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rick(at)rvairshows.com Guest
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Posted: Sat Oct 09, 2010 5:53 am Post subject: Cowl design and CHT |
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I have noticed large differences in the CHT temps of two Sukhois and three Yak 52's running similar power levels. Sukhois seem to be able to maintain cool CHT's through any operating condition and duration, with hovering at full power on a 95 degree day giving green CHT's. The cowl design on the Sukhoi has a leading edge that is an airfoil, with an inner cowl shape to speed airflow. The Yak 52 uses a cowl design that is a shell with the same external shape and no "flying" surface internally to speed airflow. All three of the Yak 52's I have flown seem to be limited to climbing Vy at max cruise. At any rate, they seem significantly hotter at much less extreme conditions. Cowl vents on the Sukhoi are a louver design. On the Yak, the cowl venting is a large opening behind the cowl. When the Sukhoi Design Bureau added horsepower with the M9R engine, they added a larger oil cooler and louvers on the side of the cowl that looked more like rear facing opening of a Yak 52. These Russians must talk to each other!
Has anyone seen the BEAR 360 that has been marketed by Skip Holm? Skip has incorporated many of his Reno race speed tricks on this M14P powered aircraft. The actual airframe design was penned by Sergei Yakovlev. Skip Holm has put a giant spinner on his Bear 360. He has also devised an added aerodynamic device placed behind the spinner to further reduce drag (unknown effect on CHT). Exhausts are flush and aim back into the airflow. The decreased back pressure has increased power. The exhaust pressure in the backwards direction contribute to airspeed. I am told that six inches of protruding exhausts give several knots of speed penalty. Much has been said about CO buildup and exhaust design. I hope they have done their homework in that respect.
My question is this: Since more Yak 52 owners are playing in extreme corners of the operating envelope with a perceived need to maintain lower cylinder head temps, should owners develop cowl mods to improve cooling? Has anyone attempted to build airfoil shapes internal to the existing cowl? Behind the spinner ? I noticed a CHT reduction of an average of 20 degrees going from the Russian V530 two blade prop without spinner to the three blade MT with large spinner. Surely there are other mods that could help manage CHT further. Am I alone in this thought? My contention is that it would be beneficial to be able to climb at any airspeed above the stall at full power as long as you wish, ala Sukhoi, without getting into yellow CHT's.
Rick Volker
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richard.goode(at)russiana Guest
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Posted: Sat Oct 09, 2010 6:26 am Post subject: Cowl design and CHT |
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The main reason that different M14P engines work at different temperatures for the same sort of flying is that few owners ever bother to change the compensating jets,and running with smaller jets [which means more fuel] will greatly reduce CHT.
The M14P runs very rich most of the time with some of the fuel going to cool the cylinders.
The jets are easy to change [5 minutes with the cowling off];come in a range 1.1to 2.1mm.
In fact it is a good idea to change the jet between summer and winter,to avoid over-cooling in winter.
Richard
Richard Goode Aerobatics
Rhodds Farm
Lyonshall
Hereford
HR5 3LW
United Kingdom
Tel: +44 (0) 1544 340120
Fax: +44 (0) 1544 340129
www.russianaeros.com
[quote] ---
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radiopicture
Joined: 23 Jun 2008 Posts: 263
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Posted: Sat Oct 09, 2010 6:34 am Post subject: Cowl design and CHT |
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Richard, I thought these compensating jets affected things primarily during throttle changes, and hesitation is the bi-product of lower CHT. Remarks?
What about the cruise mixture thingy on the back of the carb?
On Oct 9, 2010, at 10:23 AM, Richard Goode wrote:
[quote]The main reason that different M14P engines work at different temperatures for the same sort of flying is that few owners ever bother to change the compensating jets,and running with smaller jets [which means more fuel] will greatly reduce CHT.
The M14P runs very rich most of the time with some of the fuel going to cool the cylinders.
The jets are easy to change [5 minutes with the cowling off];come in a range 1.1to 2.1mm.
In fact it is a good idea to change the jet between summer and winter,to avoid over-cooling in winter.
Richard
Richard Goode Aerobatics
Rhodds Farm
Lyonshall
Hereford
HR5 3LW
United Kingdom
Tel: +44 (0) 1544 340120
Fax: +44 (0) 1544 340129
www.russianaeros.com
[quote]---
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wise(at)txc.net.au Guest
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Posted: Sat Oct 09, 2010 2:09 pm Post subject: Cowl design and CHT |
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G'Day Richard,
Years ago I belonged to the Waikerie Gliding Club and used to fly the Piper Pawnee 260HP tug.
As I never competed in any big gliding comps I undertook the role as tugmaster.
Now Waikerie can have temps over 40C on some days as the cyl temps would get pretty hot if not careful.
We found that running a bigger spinner in the summer would significantly reduce the cyl head temps as the air was possibly directed over the cyl heads more so than a smaller spinner.
I would imagine that the USA has similar climated conditions as we have here in Australia.
When flying the 52 or 18T on these hot summer days, one is always aware of the cyl temps.
The same applies as did the cyl temps on the Pawnee in the summer.
The Yaks with the big spinners run cooler.
Cheers,
Chris
[quote] ---
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viperdoc(at)mindspring.co Guest
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Posted: Sun Oct 10, 2010 5:02 am Post subject: Cowl design and CHT |
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Rick,
I've noticed a difference in the CHT on my 52 with the 18 lip stick spinner vs my 50 with the skull cap on the V450 two blade. Can't quantify the # of degrees specifically.
Doc
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mark.bitterlich(at)navy.m Guest
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Posted: Sun Oct 10, 2010 11:09 am Post subject: Cowl design and CHT |
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Chris,
I run a YAK-18T spinner on my YAK-50. It is one huge spinner. I have operated the engine with the spinner off and with the spinner on, and for the one cylinder in my engine that has a probe stuck in it, the engine ran somewhat cooler with the spinner attached exactly as you mention. What the other eight were doing, I have no idea.
That said:
I worked with a gent who put in new higher compression pistons and new cylinders (on a M-14 engine) and another person who was having very high oil temperature problems (along with cylinder head temps) on his M-14PF. In both cases, changing the fuel mixture made a DRAMATIC change in temperatures. I mean, taking it from borderline RED down into GREEN. The amount of fuel that is dumped into this engine makes a dramatic change in temps. Spinners can indeed make an impact, but not nearly as much as fuel.
Another interesting tidbit. One Sukhoi (that I had time watching) got equipped with a 9 position cylinder head temperature gage (Hubie Tolson). I wish he had done an exhaustive study (pun intended) but he mainly just wanted to make sure that he knew what the hottest jug was. What cylinder ran highest temps changed dramatically from running it on the ground, to running it in the air, which is logical. As I remember, hottest on the ground was #2. However in the air it moved around to #4 or #5 ... I am not sure of that, it was awhile ago, but anyway it tends to show that the Russians had a good idea what they were doing when they stuck the probe where they did.
Lastly, Richard Goode mentioned that the cylinder head temperature gages we use are far from being dead nuts calibrated units. I've found that to be true as well (using a calibrated IR unit by Raytec and also a Thermal IR video unit). What I found from a sampling of 5 spare probes was fairly consistent readings between probes, but a big difference between gages. I did not even try to calibrate mine, but instead just recorded where max temp REALLY was and put a mark on the gage. We tend to put faith in what a gage is telling us, but that is really far from true. Comparing cylinder head temps from one aircraft to another (without first running a calibration check on the instruments you are using) ends up being very much like comparing apples to oranges.
As an aside, I have only seen one person mess with the jets on these engines, and interestingly enough it was done exactly like we did on the drag strip. Make a change, go up and fly it, come back.. talk about it... make another change, go up and fly it, etc. I doubt if there is any real "standard" on how to mess with these things other than to have some idea what you are trying to cure and what adjustment you should start with, something I wish I knew far more about, but don't.
Mark Bitterlich
________________________________
From: owner-yak-list-server(at)matronics.com on behalf of Chris Wise
Sent: Sat 10/9/2010 7:06 PM
To: yak-list(at)matronics.com
Subject: Re: Cowl design and CHT
G'Day Richard,
Years ago I belonged to the Waikerie Gliding Club and used to fly the Piper Pawnee 260HP tug.
As I never competed in any big gliding comps I undertook the role as tugmaster.
Now Waikerie can have temps over 40C on some days as the cyl temps would get pretty hot if not careful.
We found that running a bigger spinner in the summer would significantly reduce the cyl head temps as the air was possibly directed over the cyl heads more so than a smaller spinner.
I would imagine that the USA has similar climated conditions as we have here in Australia.
When flying the 52 or 18T on these hot summer days, one is always aware of the cyl temps.
The same applies as did the cyl temps on the Pawnee in the summer.
The Yaks with the big spinners run cooler.
Cheers,
Chris
---
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radiopicture
Joined: 23 Jun 2008 Posts: 263
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Posted: Sun Oct 10, 2010 12:23 pm Post subject: Cowl design and CHT |
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Mark, when you say the fuel mixture increase made a big difference, do
you mean the click-stop adjustment on the back of the carburetor?
On Oct 10, 2010, at 3:05 PM, Bitterlich, Mark G CIV Det Cherry Point,
MALS-14 64E wrote:
[quote]
Point, MALS-14 64E" <mark.bitterlich(at)navy.mil>
Chris,
I run a YAK-18T spinner on my YAK-50. It is one huge spinner. I
have operated the engine with the spinner off and with the spinner
on, and for the one cylinder in my engine that has a probe stuck in
it, the engine ran somewhat cooler with the spinner attached exactly
as you mention. What the other eight were doing, I have no idea.
That said:
I worked with a gent who put in new higher compression pistons and
new cylinders (on a M-14 engine) and another person who was having
very high oil temperature problems (along with cylinder head temps)
on his M-14PF. In both cases, changing the fuel mixture made a
DRAMATIC change in temperatures. I mean, taking it from borderline
RED down into GREEN. The amount of fuel that is dumped into this
engine makes a dramatic change in temps. Spinners can indeed make
an impact, but not nearly as much as fuel.
Another interesting tidbit. One Sukhoi (that I had time watching)
got equipped with a 9 position cylinder head temperature gage (Hubie
Tolson). I wish he had done an exhaustive study (pun intended) but
he mainly just wanted to make sure that he knew what the hottest jug
was. What cylinder ran highest temps changed dramatically from
running it on the ground, to running it in the air, which is
logical. As I remember, hottest on the ground was #2. However in
the air it moved around to #4 or #5 ... I am not sure of that, it
was awhile ago, but anyway it tends to show that the Russians had a
good idea what they were doing when they stuck the probe where they
did.
Lastly, Richard Goode mentioned that the cylinder head temperature
gages we use are far from being dead nuts calibrated units. I've
found that to be true as well (using a calibrated IR unit by Raytec
and also a Thermal IR video unit). What I found from a sampling of
5 spare probes was fairly consistent readings between probes, but a
big difference between gages. I did not even try to calibrate
mine, but instead just recorded where max temp REALLY was and put a
mark on the gage. We tend to put faith in what a gage is telling
us, but that is really far from true. Comparing cylinder head temps
from one aircraft to another (without first running a calibration
check on the instruments you are using) ends up being very much like
comparing apples to oranges.
As an aside, I have only seen one person mess with the jets on these
engines, and interestingly enough it was done exactly like we did on
the drag strip. Make a change, go up and fly it, come back.. talk
about it... make another change, go up and fly it, etc. I doubt if
there is any real "standard" on how to mess with these things other
than to have some idea what you are trying to cure and what
adjustment you should start with, something I wish I knew far more
about, but don't.
Mark Bitterlich
________________________________
From: owner-yak-list-server(at)matronics.com on behalf of Chris Wise
Sent: Sat 10/9/2010 7:06 PM
To: yak-list(at)matronics.com
Subject: Re: Cowl design and CHT
G'Day Richard,
Years ago I belonged to the Waikerie Gliding Club and used to fly
the Piper Pawnee 260HP tug.
As I never competed in any big gliding comps I undertook the role as
tugmaster.
Now Waikerie can have temps over 40C on some days as the cyl temps
would get pretty hot if not careful.
We found that running a bigger spinner in the summer would
significantly reduce the cyl head temps as the air was possibly
directed over the cyl heads more so than a smaller spinner.
I would imagine that the USA has similar climated conditions as we
have here in Australia.
When flying the 52 or 18T on these hot summer days, one is always
aware of the cyl temps.
The same applies as did the cyl temps on the Pawnee in the summer.
The Yaks with the big spinners run cooler.
Cheers,
Chris
---
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rick(at)rvairshows.com Guest
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Posted: Sun Oct 10, 2010 3:22 pm Post subject: Cowl design and CHT |
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Mark,
I use a JPI engine analyzer on my SU26. On the ground, they are all within 10 degrees of each other- almost equal. In the air, #2 is the hottest, followed very closely by #1, then #9. The coolest cylinder is #4 (master cylinder), followed closely by #5. EGT is interesting: The closest spread that I get is about 70 degrees. 80 degrees for economy cruise. 110 for max cruise. The worst in flight is 150 degrees diff. at full power. I can run it up at 65% rpm on the ground and it will take about 20 sec after a long taxi (250 degrees EGT diff meaning loaded up plugs) to get to a low of 110 degrees diff. That is when I shut down, assuming plugs are all cleared. I have run two M14P engines on this JPI monitor and have seen the same profile on each. The EGT diff is normal for a carbureted engine. The #7 cylinder has very low EGT and is responsible for most of the differential. Initially on the last engine, I thought this might be due to some problems with the cylinder and compression was a little lower than the rest on a high time engine, I replaced it. The new cylinder had the same low EGT. My new M14P engine again has the same profile. I am kicking myself for wasting the new cylinder on what is likely the position of the probe on the #7 exhaust stack, or the shape of the exhaust stack, or that the fuel happens to sling into this cylinder more( the engine monitor suggests this) on every engine. All in, you can second guess these things a bit too much. I have fun keeping all cylinders from getting too cool on descents. I get to watch the shock cooling alert when I do gyroscopic or severely yawed maneuvers, as air flow gets rerouted. Flying inverted brings the coolest cylinders up in temp and the previously hottest cylinders down. The only reason to use the EGT on this motor would be to diagnose cylinder problems, or to back up ignition timing. I have been told that Swift fuel has a delayed burn, requires about a 3 degree advance of timing with corresponding EGT rise to get 100% power. Leaving tim!
ing stoc
k gives about 97% power but 15 % more range from the same fuel volume. I have seen an improperly timed M14P crack rings on every cylinder. I will bet this would have showed on the EGT if the pilot had a similar JPI and knew what to expect. The JPI probes test accurately.
My old SU29 had the pilot in command panel CHT on #2 cylinder and the passenger panel CHT on #4. This could be viewed with a little leaning around the head of the passenger, giving all the info you need. I always thought the poor man's engine monitor would be an extra Russian CHT on this #4 cylinder- it takes up very little space and they are plentiful on the used market. If anyone likes, I will send the JPI monitor profile of the air show I did in 95 degree F weather. it is a ground start with complete warm up and ground start for the routine. It carries on for 8 minutes at full manifold pressure and 99% rpm, then power is reduced with a landing one minute later.
Rick Volker
www.rvairshows,com
On Oct 10, 2010, at 3:05 PM, Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E wrote:
[quote]
Chris,
I run a YAK-18T spinner on my YAK-50. It is one huge spinner. I have operated the engine with the spinner off and with the spinner on, and for the one cylinder in my engine that has a probe stuck in it, the engine ran somewhat cooler with the spinner attached exactly as you mention. What the other eight were doing, I have no idea.
That said:
I worked with a gent who put in new higher compression pistons and new cylinders (on a M-14 engine) and another person who was having very high oil temperature problems (along with cylinder head temps) on his M-14PF. In both cases, changing the fuel mixture made a DRAMATIC change in temperatures. I mean, taking it from borderline RED down into GREEN. The amount of fuel that is dumped into this engine makes a dramatic change in temps. Spinners can indeed make an impact, but not nearly as much as fuel.
Another interesting tidbit. One Sukhoi (that I had time watching) got equipped with a 9 position cylinder head temperature gage (Hubie Tolson). I wish he had done an exhaustive study (pun intended) but he mainly just wanted to make sure that he knew what the hottest jug was. What cylinder ran highest temps changed dramatically from running it on the ground, to running it in the air, which is logical. As I remember, hottest on the ground was #2. However in the air it moved around to #4 or #5 ... I am not sure of that, it was awhile ago, but anyway it tends to show that the Russians had a good idea what they were doing when they stuck the probe where they did.
Lastly, Richard Goode mentioned that the cylinder head temperature gages we use are far from being dead nuts calibrated units. I've found that to be true as well (using a calibrated IR unit by Raytec and also a Thermal IR video unit). What I found from a sampling of 5 spare probes was fairly consistent readings between probes, but a big difference between gages. I did not even try to calibrate mine, but instead just recorded where max temp REALLY was and put a mark on the gage. We tend to put faith in what a gage is telling us, but that is really far from true. Comparing cylinder head temps from one aircraft to another (without first running a calibration check on the instruments you are using) ends up being very much like comparing apples to oranges.
As an aside, I have only seen one person mess with the jets on these engines, and interestingly enough it was done exactly like we did on the drag strip. Make a change, go up and fly it, come back.. talk about it... make another change, go up and fly it, etc. I doubt if there is any real "standard" on how to mess with these things other than to have some idea what you are trying to cure and what adjustment you should start with, something I wish I knew far more about, but don't.
Mark Bitterlich
________________________________
From: owner-yak-list-server(at)matronics.com on behalf of Chris Wise
Sent: Sat 10/9/2010 7:06 PM
To: yak-list(at)matronics.com
Subject: Re: Cowl design and CHT
G'Day Richard,
Years ago I belonged to the Waikerie Gliding Club and used to fly the Piper Pawnee 260HP tug.
As I never competed in any big gliding comps I undertook the role as tugmaster.
Now Waikerie can have temps over 40C on some days as the cyl temps would get pretty hot if not careful.
We found that running a bigger spinner in the summer would significantly reduce the cyl head temps as the air was possibly directed over the cyl heads more so than a smaller spinner.
I would imagine that the USA has similar climated conditions as we have here in Australia.
When flying the 52 or 18T on these hot summer days, one is always aware of the cyl temps.
The same applies as did the cyl temps on the Pawnee in the summer.
The Yaks with the big spinners run cooler.
Cheers,
Chris
---
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mark.bitterlich(at)navy.m Guest
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Posted: Sun Oct 10, 2010 3:35 pm Post subject: Cowl design and CHT |
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No, I am talking about the main mixture jet, which Richard Goode refers to as the "Compensation Jet". Although yes, I have messed with the one you are talking about.
Being perfectly clear here Eric, I was just a spectator. I profess no special knowledge on this darn thing other than:
1. I have seen where adjusting the accelerator pump jet will cure hesitation on throttle advancement versus just plugging the darn thing, which was the initial cure until smart people figured out you could buy a jet kit and adjust it accordingly. I am VERY familiar with this kind of thing because you run into it a lot adjusting a Holley carb where there are many MANY adjustments for the amount of fuel you dump in when you move the throttle plates.
2. The main jet or "Compensation Jet" has the ability to dramatically change fuel mixture in the mid to high range of engine RPM.
I would very much love to hear Richard Goode go into more detail on how he determines how much change to make based on engine indications. He obviously has way more experience than I do. I have seen it done ONCE... but it worked, in a big way.
I would also like to hear Richard tell me how many clicks on the back of the carb equates to one jet size....if that is the case at all.
Mark
________________________________
From: owner-yak-list-server(at)matronics.com on behalf of Eric Wobschall
Sent: Sun 10/10/2010 4:20 PM
To: yak-list(at)matronics.com
Subject: Re: Cowl design and CHT
Mark, when you say the fuel mixture increase made a big difference, do
you mean the click-stop adjustment on the back of the carburetor?
On Oct 10, 2010, at 3:05 PM, Bitterlich, Mark G CIV Det Cherry Point,
MALS-14 64E wrote:
[quote]
Point, MALS-14 64E" <mark.bitterlich(at)navy.mil>
Chris,
I run a YAK-18T spinner on my YAK-50. It is one huge spinner. I
have operated the engine with the spinner off and with the spinner
on, and for the one cylinder in my engine that has a probe stuck in
it, the engine ran somewhat cooler with the spinner attached exactly
as you mention. What the other eight were doing, I have no idea.
That said:
I worked with a gent who put in new higher compression pistons and
new cylinders (on a M-14 engine) and another person who was having
very high oil temperature problems (along with cylinder head temps)
on his M-14PF. In both cases, changing the fuel mixture made a
DRAMATIC change in temperatures. I mean, taking it from borderline
RED down into GREEN. The amount of fuel that is dumped into this
engine makes a dramatic change in temps. Spinners can indeed make
an impact, but not nearly as much as fuel.
Another interesting tidbit. One Sukhoi (that I had time watching)
got equipped with a 9 position cylinder head temperature gage (Hubie
Tolson). I wish he had done an exhaustive study (pun intended) but
he mainly just wanted to make sure that he knew what the hottest jug
was. What cylinder ran highest temps changed dramatically from
running it on the ground, to running it in the air, which is
logical. As I remember, hottest on the ground was #2. However in
the air it moved around to #4 or #5 ... I am not sure of that, it
was awhile ago, but anyway it tends to show that the Russians had a
good idea what they were doing when they stuck the probe where they
did.
Lastly, Richard Goode mentioned that the cylinder head temperature
gages we use are far from being dead nuts calibrated units. I've
found that to be true as well (using a calibrated IR unit by Raytec
and also a Thermal IR video unit). What I found from a sampling of
5 spare probes was fairly consistent readings between probes, but a
big difference between gages. I did not even try to calibrate
mine, but instead just recorded where max temp REALLY was and put a
mark on the gage. We tend to put faith in what a gage is telling
us, but that is really far from true. Comparing cylinder head temps
from one aircraft to another (without first running a calibration
check on the instruments you are using) ends up being very much like
comparing apples to oranges.
As an aside, I have only seen one person mess with the jets on these
engines, and interestingly enough it was done exactly like we did on
the drag strip. Make a change, go up and fly it, come back.. talk
about it... make another change, go up and fly it, etc. I doubt if
there is any real "standard" on how to mess with these things other
than to have some idea what you are trying to cure and what
adjustment you should start with, something I wish I knew far more
about, but don't.
Mark Bitterlich
________________________________
From: owner-yak-list-server(at)matronics.com on behalf of Chris Wise
Sent: Sat 10/9/2010 7:06 PM
To: yak-list(at)matronics.com
Subject: Re: Cowl design and CHT
G'Day Richard,
Years ago I belonged to the Waikerie Gliding Club and used to fly
the Piper Pawnee 260HP tug.
As I never competed in any big gliding comps I undertook the role as
tugmaster.
Now Waikerie can have temps over 40C on some days as the cyl temps
would get pretty hot if not careful.
We found that running a bigger spinner in the summer would
significantly reduce the cyl head temps as the air was possibly
directed over the cyl heads more so than a smaller spinner.
I would imagine that the USA has similar climated conditions as we
have here in Australia.
When flying the 52 or 18T on these hot summer days, one is always
aware of the cyl temps.
The same applies as did the cyl temps on the Pawnee in the summer.
The Yaks with the big spinners run cooler.
Cheers,
Chris
---
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mark.bitterlich(at)navy.m Guest
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Posted: Sun Oct 10, 2010 3:48 pm Post subject: Cowl design and CHT |
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|
Actually, I have no idea how to do what Richard was saying. I watched a gent with a handful of parts mess with the darn thing and in the end the EGT and Cylinder Head temps along with oil temps changed dramatically.
I really just do not fully understand this pressure carb.
Mark
________________________________
From: owner-yak-list-server(at)matronics.com on behalf of Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E
Sent: Sun 10/10/2010 7:32 PM
To: yak-list(at)matronics.com
Subject: RE: Cowl design and CHT
No, I am talking about the main mixture jet, which Richard Goode refers to as the "Compensation Jet". Although yes, I have messed with the one you are talking about.
Being perfectly clear here Eric, I was just a spectator. I profess no special knowledge on this darn thing other than:
1. I have seen where adjusting the accelerator pump jet will cure hesitation on throttle advancement versus just plugging the darn thing, which was the initial cure until smart people figured out you could buy a jet kit and adjust it accordingly. I am VERY familiar with this kind of thing because you run into it a lot adjusting a Holley carb where there are many MANY adjustments for the amount of fuel you dump in when you move the throttle plates.
2. The main jet or "Compensation Jet" has the ability to dramatically change fuel mixture in the mid to high range of engine RPM.
I would very much love to hear Richard Goode go into more detail on how he determines how much change to make based on engine indications. He obviously has way more experience than I do. I have seen it done ONCE... but it worked, in a big way.
I would also like to hear Richard tell me how many clicks on the back of the carb equates to one jet size....if that is the case at all.
Mark
________________________________
From: owner-yak-list-server(at)matronics.com on behalf of Eric Wobschall
Sent: Sun 10/10/2010 4:20 PM
To: yak-list(at)matronics.com
Subject: Re: Cowl design and CHT
Mark, when you say the fuel mixture increase made a big difference, do
you mean the click-stop adjustment on the back of the carburetor?
On Oct 10, 2010, at 3:05 PM, Bitterlich, Mark G CIV Det Cherry Point,
MALS-14 64E wrote:
[quote]
Point, MALS-14 64E" <mark.bitterlich(at)navy.mil>
Chris,
I run a YAK-18T spinner on my YAK-50. It is one huge spinner. I
have operated the engine with the spinner off and with the spinner
on, and for the one cylinder in my engine that has a probe stuck in
it, the engine ran somewhat cooler with the spinner attached exactly
as you mention. What the other eight were doing, I have no idea.
That said:
I worked with a gent who put in new higher compression pistons and
new cylinders (on a M-14 engine) and another person who was having
very high oil temperature problems (along with cylinder head temps)
on his M-14PF. In both cases, changing the fuel mixture made a
DRAMATIC change in temperatures. I mean, taking it from borderline
RED down into GREEN. The amount of fuel that is dumped into this
engine makes a dramatic change in temps. Spinners can indeed make
an impact, but not nearly as much as fuel.
Another interesting tidbit. One Sukhoi (that I had time watching)
got equipped with a 9 position cylinder head temperature gage (Hubie
Tolson). I wish he had done an exhaustive study (pun intended) but
he mainly just wanted to make sure that he knew what the hottest jug
was. What cylinder ran highest temps changed dramatically from
running it on the ground, to running it in the air, which is
logical. As I remember, hottest on the ground was #2. However in
the air it moved around to #4 or #5 ... I am not sure of that, it
was awhile ago, but anyway it tends to show that the Russians had a
good idea what they were doing when they stuck the probe where they
did.
Lastly, Richard Goode mentioned that the cylinder head temperature
gages we use are far from being dead nuts calibrated units. I've
found that to be true as well (using a calibrated IR unit by Raytec
and also a Thermal IR video unit). What I found from a sampling of
5 spare probes was fairly consistent readings between probes, but a
big difference between gages. I did not even try to calibrate
mine, but instead just recorded where max temp REALLY was and put a
mark on the gage. We tend to put faith in what a gage is telling
us, but that is really far from true. Comparing cylinder head temps
from one aircraft to another (without first running a calibration
check on the instruments you are using) ends up being very much like
comparing apples to oranges.
As an aside, I have only seen one person mess with the jets on these
engines, and interestingly enough it was done exactly like we did on
the drag strip. Make a change, go up and fly it, come back.. talk
about it... make another change, go up and fly it, etc. I doubt if
there is any real "standard" on how to mess with these things other
than to have some idea what you are trying to cure and what
adjustment you should start with, something I wish I knew far more
about, but don't.
Mark Bitterlich
________________________________
From: owner-yak-list-server(at)matronics.com on behalf of Chris Wise
Sent: Sat 10/9/2010 7:06 PM
To: yak-list(at)matronics.com
Subject: Re: Cowl design and CHT
G'Day Richard,
Years ago I belonged to the Waikerie Gliding Club and used to fly
the Piper Pawnee 260HP tug.
As I never competed in any big gliding comps I undertook the role as
tugmaster.
Now Waikerie can have temps over 40C on some days as the cyl temps
would get pretty hot if not careful.
We found that running a bigger spinner in the summer would
significantly reduce the cyl head temps as the air was possibly
directed over the cyl heads more so than a smaller spinner.
I would imagine that the USA has similar climated conditions as we
have here in Australia.
When flying the 52 or 18T on these hot summer days, one is always
aware of the cyl temps.
The same applies as did the cyl temps on the Pawnee in the summer.
The Yaks with the big spinners run cooler.
Cheers,
Chris
---
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mark.bitterlich(at)navy.m Guest
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Posted: Sun Oct 10, 2010 4:02 pm Post subject: Cowl design and CHT |
|
|
I am going to go WAY out on a limb here and ask for comments to this statement: (Richard? HELP PLEASE!)
My very vague understanding is that the needle click adjustment on the rear of the carb adjusts the initial set point of the fuel metering tube. Thus it is basically set for mixture // fuel consumption in the mid range of the engine as the throttle linkage comes off idle and into initial cruise. This metering rod comes off the stop as you come above idle, and greatly impacts how much fuel the engine gets from that point to the point where you get to much higher power settings.
On the other hand, the compensation or "suction jet" while impacting mixture across the entire engine operating range to some degree, is mainly meant to adjust top end power ratings. I.E. Takeoff power and maybe high end cruise settings.
In other words, you would adjust the suction jet at wide open throttle first, and get that to where the engine is performing right. THEN you would adjust the initial metering rod adjustment with the "click knob" on the rear of the carb to control off idle to high mid range power settings.
Please tell me if I am even in the ball park here.
Mark Bitterlich
________________________________
From: owner-yak-list-server(at)matronics.com on behalf of Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E
Sent: Sun 10/10/2010 7:32 PM
To: yak-list(at)matronics.com
Subject: RE: Cowl design and CHT
No, I am talking about the main mixture jet, which Richard Goode refers to as the "Compensation Jet". Although yes, I have messed with the one you are talking about.
Being perfectly clear here Eric, I was just a spectator. I profess no special knowledge on this darn thing other than:
1. I have seen where adjusting the accelerator pump jet will cure hesitation on throttle advancement versus just plugging the darn thing, which was the initial cure until smart people figured out you could buy a jet kit and adjust it accordingly. I am VERY familiar with this kind of thing because you run into it a lot adjusting a Holley carb where there are many MANY adjustments for the amount of fuel you dump in when you move the throttle plates.
2. The main jet or "Compensation Jet" has the ability to dramatically change fuel mixture in the mid to high range of engine RPM.
I would very much love to hear Richard Goode go into more detail on how he determines how much change to make based on engine indications. He obviously has way more experience than I do. I have seen it done ONCE... but it worked, in a big way.
I would also like to hear Richard tell me how many clicks on the back of the carb equates to one jet size....if that is the case at all.
Mark
________________________________
From: owner-yak-list-server(at)matronics.com on behalf of Eric Wobschall
Sent: Sun 10/10/2010 4:20 PM
To: yak-list(at)matronics.com
Subject: Re: Cowl design and CHT
Mark, when you say the fuel mixture increase made a big difference, do
you mean the click-stop adjustment on the back of the carburetor?
On Oct 10, 2010, at 3:05 PM, Bitterlich, Mark G CIV Det Cherry Point,
MALS-14 64E wrote:
[quote]
Point, MALS-14 64E" <mark.bitterlich(at)navy.mil>
Chris,
I run a YAK-18T spinner on my YAK-50. It is one huge spinner. I
have operated the engine with the spinner off and with the spinner
on, and for the one cylinder in my engine that has a probe stuck in
it, the engine ran somewhat cooler with the spinner attached exactly
as you mention. What the other eight were doing, I have no idea.
That said:
I worked with a gent who put in new higher compression pistons and
new cylinders (on a M-14 engine) and another person who was having
very high oil temperature problems (along with cylinder head temps)
on his M-14PF. In both cases, changing the fuel mixture made a
DRAMATIC change in temperatures. I mean, taking it from borderline
RED down into GREEN. The amount of fuel that is dumped into this
engine makes a dramatic change in temps. Spinners can indeed make
an impact, but not nearly as much as fuel.
Another interesting tidbit. One Sukhoi (that I had time watching)
got equipped with a 9 position cylinder head temperature gage (Hubie
Tolson). I wish he had done an exhaustive study (pun intended) but
he mainly just wanted to make sure that he knew what the hottest jug
was. What cylinder ran highest temps changed dramatically from
running it on the ground, to running it in the air, which is
logical. As I remember, hottest on the ground was #2. However in
the air it moved around to #4 or #5 ... I am not sure of that, it
was awhile ago, but anyway it tends to show that the Russians had a
good idea what they were doing when they stuck the probe where they
did.
Lastly, Richard Goode mentioned that the cylinder head temperature
gages we use are far from being dead nuts calibrated units. I've
found that to be true as well (using a calibrated IR unit by Raytec
and also a Thermal IR video unit). What I found from a sampling of
5 spare probes was fairly consistent readings between probes, but a
big difference between gages. I did not even try to calibrate
mine, but instead just recorded where max temp REALLY was and put a
mark on the gage. We tend to put faith in what a gage is telling
us, but that is really far from true. Comparing cylinder head temps
from one aircraft to another (without first running a calibration
check on the instruments you are using) ends up being very much like
comparing apples to oranges.
As an aside, I have only seen one person mess with the jets on these
engines, and interestingly enough it was done exactly like we did on
the drag strip. Make a change, go up and fly it, come back.. talk
about it... make another change, go up and fly it, etc. I doubt if
there is any real "standard" on how to mess with these things other
than to have some idea what you are trying to cure and what
adjustment you should start with, something I wish I knew far more
about, but don't.
Mark Bitterlich
________________________________
From: owner-yak-list-server(at)matronics.com on behalf of Chris Wise
Sent: Sat 10/9/2010 7:06 PM
To: yak-list(at)matronics.com
Subject: Re: Cowl design and CHT
G'Day Richard,
Years ago I belonged to the Waikerie Gliding Club and used to fly
the Piper Pawnee 260HP tug.
As I never competed in any big gliding comps I undertook the role as
tugmaster.
Now Waikerie can have temps over 40C on some days as the cyl temps
would get pretty hot if not careful.
We found that running a bigger spinner in the summer would
significantly reduce the cyl head temps as the air was possibly
directed over the cyl heads more so than a smaller spinner.
I would imagine that the USA has similar climated conditions as we
have here in Australia.
When flying the 52 or 18T on these hot summer days, one is always
aware of the cyl temps.
The same applies as did the cyl temps on the Pawnee in the summer.
The Yaks with the big spinners run cooler.
Cheers,
Chris
---
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mark.bitterlich(at)navy.m Guest
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Posted: Sun Oct 10, 2010 4:21 pm Post subject: Cowl design and CHT |
|
|
Now THIS is good test information.
Thank you Rick. Yes, I very much would like to see that data.
A factoid is that my temperature checks ....which differ from yours ... first were looked at on a YAK-50 (mine) that has no shutters on the cowl. In other words, the air has a straight shot into the engine except for the huge spinner. In that way it is kind of like a Suke with an Iris fully open.
What I do not understand is the test data I got from my friend Hube with the SU-26 using the same JPI engine monitor that apparently you have.
Another thing that you said that grabbed my interest was the position of EGT probes in the exhaust stacks. This is kind of off-topic, but a lot of experimentation has been done in this area with smoke systems. People have assumed that putting the smoke injector higher up in the manifold would result in more burn and thus more smoke. That did not happen. There is clearly a position just somewhat above the exhaust exit that is best. This leads me to wonder just what kind of weird flow is going on in a radials exhaust systems, where a "ring" is used versus individual stacks going right to a collection point and then out.
Just put a picture in your mind of an engine firing on every other cylinder and then look at that exhaust ring and imagine what the gas pressures and flows might look like and how they behave. In drag racing engines, we work very VERY hard to equalize back pressure to every cylinder using equal length exhaust tubing to a central collector. In fact, Tom Johnson on his YAK-50 has a custom made exhaust system that does exactly that. This ALWAYS increases horsepower, and equalizes exhaust gas temps to a great extent. So, it makes me wonder... can we trust exhaust gas readings on an engine using a central "ring" or not? If not, how much of a spread would there be?
Is it a good idea to run the engine on the ground using a thermal imager and trust that data? Or just what?
In the end, I gave up. What I decided is that what I thought I knew, really wasn't trustworthy. I think maybe that the "tune for best performance" idea may just be the best bet.
With that in mind, I clearly do not know enough about these engines to even have a valid opinion.
Mark Bitterlich
________________________________
From: owner-yak-list-server(at)matronics.com on behalf of RICHARD VOLKER
Sent: Sun 10/10/2010 7:18 PM
To: yak-list(at)matronics.com
Subject: Re: Cowl design and CHT
Mark,
I use a JPI engine analyzer on my SU26. On the ground, they are all within 10 degrees of each other- almost equal. In the air, #2 is the hottest, followed very closely by #1, then #9. The coolest cylinder is #4 (master cylinder), followed closely by #5. EGT is interesting: The closest spread that I get is about 70 degrees. 80 degrees for economy cruise. 110 for max cruise. The worst in flight is 150 degrees diff. at full power. I can run it up at 65% rpm on the ground and it will take about 20 sec after a long taxi (250 degrees EGT diff meaning loaded up plugs) to get to a low of 110 degrees diff. That is when I shut down, assuming plugs are all cleared. I have run two M14P engines on this JPI monitor and have seen the same profile on each. The EGT diff is normal for a carbureted engine. The #7 cylinder has very low EGT and is responsible for most of the differential. Initially on the last engine, I thought this might be due to some problems with the cylinder and co!
mpression was a little lower than the rest on a high time engine, I replaced it. The new cylinder had the same low EGT. My new M14P engine again has the same profile. I am kicking myself for wasting the new cylinder on what is likely the position of the probe on the #7 exhaust stack, or the shape of the exhaust stack, or that the fuel happens to sling into this cylinder more( the engine monitor suggests this) on every engine. All in, you can second guess these things a bit too much. I have fun keeping all cylinders from getting too cool on descents. I get to watch the shock cooling alert when I do gyroscopic or severely yawed maneuvers, as air flow gets rerouted. Flying inverted brings the coolest cylinders up in temp and the previously hottest cylinders down. The only reason to use the EGT on this motor would be to diagnose cylinder problems, or to back up ignition timing. I have been told that Swift fuel has a delayed burn, requires about a 3 degree advance of timi!
ng with corresponding EGT rise to get 100% power. Leaving tim!
ing stoc
k gives about 97% power but 15 % more range from the same fuel volume. I have seen an improperly timed M14P crack rings on every cylinder. I will bet this would have showed on the EGT if the pilot had a similar JPI and knew what to expect. The JPI probes test accurately.
My old SU29 had the pilot in command panel CHT on #2 cylinder and the passenger panel CHT on #4. This could be viewed with a little leaning around the head of the passenger, giving all the info you need. I always thought the poor man's engine monitor would be an extra Russian CHT on this #4 cylinder- it takes up very little space and they are plentiful on the used market. If anyone likes, I will send the JPI monitor profile of the air show I did in 95 degree F weather. it is a ground start with complete warm up and ground start for the routine. It carries on for 8 minutes at full manifold pressure and 99% rpm, then power is reduced with a landing one minute later.
Rick Volker
www.rvairshows,com
On Oct 10, 2010, at 3:05 PM, Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E wrote:
[quote]
Chris,
I run a YAK-18T spinner on my YAK-50. It is one huge spinner. I have operated the engine with the spinner off and with the spinner on, and for the one cylinder in my engine that has a probe stuck in it, the engine ran somewhat cooler with the spinner attached exactly as you mention. What the other eight were doing, I have no idea.
That said:
I worked with a gent who put in new higher compression pistons and new cylinders (on a M-14 engine) and another person who was having very high oil temperature problems (along with cylinder head temps) on his M-14PF. In both cases, changing the fuel mixture made a DRAMATIC change in temperatures. I mean, taking it from borderline RED down into GREEN. The amount of fuel that is dumped into this engine makes a dramatic change in temps. Spinners can indeed make an impact, but not nearly as much as fuel.
Another interesting tidbit. One Sukhoi (that I had time watching) got equipped with a 9 position cylinder head temperature gage (Hubie Tolson). I wish he had done an exhaustive study (pun intended) but he mainly just wanted to make sure that he knew what the hottest jug was. What cylinder ran highest temps changed dramatically from running it on the ground, to running it in the air, which is logical. As I remember, hottest on the ground was #2. However in the air it moved around to #4 or #5 ... I am not sure of that, it was awhile ago, but anyway it tends to show that the Russians had a good idea what they were doing when they stuck the probe where they did.
Lastly, Richard Goode mentioned that the cylinder head temperature gages we use are far from being dead nuts calibrated units. I've found that to be true as well (using a calibrated IR unit by Raytec and also a Thermal IR video unit). What I found from a sampling of 5 spare probes was fairly consistent readings between probes, but a big difference between gages. I did not even try to calibrate mine, but instead just recorded where max temp REALLY was and put a mark on the gage. We tend to put faith in what a gage is telling us, but that is really far from true. Comparing cylinder head temps from one aircraft to another (without first running a calibration check on the instruments you are using) ends up being very much like comparing apples to oranges.
As an aside, I have only seen one person mess with the jets on these engines, and interestingly enough it was done exactly like we did on the drag strip. Make a change, go up and fly it, come back.. talk about it... make another change, go up and fly it, etc. I doubt if there is any real "standard" on how to mess with these things other than to have some idea what you are trying to cure and what adjustment you should start with, something I wish I knew far more about, but don't.
Mark Bitterlich
________________________________
From: owner-yak-list-server(at)matronics.com on behalf of Chris Wise
Sent: Sat 10/9/2010 7:06 PM
To: yak-list(at)matronics.com
Subject: Re: Cowl design and CHT
G'Day Richard,
Years ago I belonged to the Waikerie Gliding Club and used to fly the Piper Pawnee 260HP tug.
As I never competed in any big gliding comps I undertook the role as tugmaster.
Now Waikerie can have temps over 40C on some days as the cyl temps would get pretty hot if not careful.
We found that running a bigger spinner in the summer would significantly reduce the cyl head temps as the air was possibly directed over the cyl heads more so than a smaller spinner.
I would imagine that the USA has similar climated conditions as we have here in Australia.
When flying the 52 or 18T on these hot summer days, one is always aware of the cyl temps.
The same applies as did the cyl temps on the Pawnee in the summer.
The Yaks with the big spinners run cooler.
Cheers,
Chris
---
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radiopicture
Joined: 23 Jun 2008 Posts: 263
|
Posted: Sun Oct 10, 2010 4:31 pm Post subject: Cowl design and CHT |
|
|
Mark:
I had what I considered to be somewhat high CHT on a VERY LOW TIME first run factory engine. This was with factory settings which I was loathe to touch. I'm in Western NY state, so you'd think average settings would cover me. I have checked and tightened various things, including cylinder and supercharger case gland nuts. The temps seem to have crept down. Maybe some of it is break-in, although Jill G. would say break-in is done on a test stand before it sees an airplane. Maybe I've gotten better at managing climb angle, etc.
Rick Volker has been around this plane and felt there was an issue compared with the Sukhois he owned. He also feels spinner and cowl play a big part. as you've read.
I did ring up Vladamir Yastremski (sp?), and he said my temps were well within acceptable limits, and to worry more about low temps. Dennis S. has said about the same thing in the past. Rick suggested test where I climb-out at Vy to 5000 ft. I tried that, and I kept it under 210 C, and then leveled off at max cruise, after which time it stayed in the high green. So that wasn't bad. Now keep in mind this was at 63 degrees ambient at the departure airport (KBQR 752').
About all of these jets: Richard Goode says they all need adjusting, and I think it was Sergei Prolegiev who suggested that I get it out of my head that it left the factory perfectly adjusted. I do have a slight hesitation when I feed power back in on final, but it's not scary. I have all of the different jets, if only I knew what I was doing. I was hoping one or two clockwise clicks on the cruise mixture adjustment would enrichen the mixture enough to make my plane and I happy. I do have great fuel economy, so maybe I'm lean.
Here's my gage and the Yak-UK translated DOSAAF manual I usually go by. Remarks, anyone? -Eric
[img]cid:F0FADBD6-963C-42F6-A4AE-776FA40324EC(at)home[/img]
On Oct 10, 2010, at 7:32 PM, Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E wrote:
[quote]--> Yak-List message posted by: "Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E" <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)>
No, I am talking about the main mixture jet, which Richard Goode refers to as the "Compensation Jet". Although yes, I have messed with the one you are talking about.
Being perfectly clear here Eric, I was just a spectator. I profess no special knowledge on this darn thing other than:
1. I have seen where adjusting the accelerator pump jet will cure hesitation on throttle advancement versus just plugging the darn thing, which was the initial cure until smart people figured out you could buy a jet kit and adjust it accordingly. I am VERY familiar with this kind of thing because you run into it a lot adjusting a Holley carb where there are many MANY adjustments for the amount of fuel you dump in when you move the throttle plates.
2. The main jet or "Compensation Jet" has the ability to dramatically change fuel mixture in the mid to high range of engine RPM.
I would very much love to hear Richard Goode go into more detail on how he determines how much change to make based on engine indications. He obviously has way more experience than I do. I have seen it done ONCE... but it worked, in a big way.
I would also like to hear Richard tell me how many clicks on the back of the carb equates to one jet size....if that is the case at all.
Mark
________________________________
From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) on behalf of Eric Wobschall
Sent: Sun 10/10/2010 4:20 PM
To: yak-list(at)matronics.com (yak-list(at)matronics.com)
Subject: Re: Cowl design and CHT
--> Yak-List message posted by: Eric Wobschall <eric(at)buffaloskyline.com (eric(at)buffaloskyline.com)>
Mark, when you say the fuel mixture increase made a big difference, do
you mean the click-stop adjustment on the back of the carburetor?
On Oct 10, 2010, at 3:05 PM, Bitterlich, Mark G CIV Det Cherry Point,
MALS-14 64E wrote:
[quote]--> Yak-List message posted by: "Bitterlich, Mark G CIV Det Cherry
Point, MALS-14 64E" <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)>
Chris,
I run a YAK-18T spinner on my YAK-50. It is one huge spinner. I
have operated the engine with the spinner off and with the spinner
on, and for the one cylinder in my engine that has a probe stuck in
it, the engine ran somewhat cooler with the spinner attached exactly
as you mention. What the other eight were doing, I have no idea.
That said:
I worked with a gent who put in new higher compression pistons and
new cylinders (on a M-14 engine) and another person who was having
very high oil temperature problems (along with cylinder head temps)
on his M-14PF. In both cases, changing the fuel mixture made a
DRAMATIC change in temperatures. I mean, taking it from borderline
RED down into GREEN. The amount of fuel that is dumped into this
engine makes a dramatic change in temps. Spinners can indeed make
an impact, but not nearly as much as fuel.
Another interesting tidbit. One Sukhoi (that I had time watching)
got equipped with a 9 position cylinder head temperature gage (Hubie
Tolson). I wish he had done an exhaustive study (pun intended) but
he mainly just wanted to make sure that he knew what the hottest jug
was. What cylinder ran highest temps changed dramatically from
running it on the ground, to running it in the air, which is
logical. As I remember, hottest on the ground was #2. However in
the air it moved around to #4 or #5 ... I am not sure of that, it
was awhile ago, but anyway it tends to show that the Russians had a
good idea what they were doing when they stuck the probe where they
did.
Lastly, Richard Goode mentioned that the cylinder head temperature
gages we use are far from being dead nuts calibrated units. I've
found that to be true as well (using a calibrated IR unit by Raytec
and also a Thermal IR video unit). What I found from a sampling of
5 spare probes was fairly consistent readings between probes, but a
big difference between gages. I did not even try to calibrate
mine, but instead just recorded where max temp REALLY was and put a
mark on the gage. We tend to put faith in what a gage is telling
us, but that is really far from true. Comparing cylinder head temps
from one aircraft to another (without first running a calibration
check on the instruments you are using) ends up being very much like
comparing apples to oranges.
As an aside, I have only seen one person mess with the jets on these
engines, and interestingly enough it was done exactly like we did on
the drag strip. Make a change, go up and fly it, come back.. talk
about it... make another change, go up and fly it, etc. I doubt if
there is any real "standard" on how to mess with these things other
than to have some idea what you are trying to cure and what
adjustment you should start with, something I wish I knew far more
about, but don't.
Mark Bitterlich
________________________________
From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) on behalf of Chris Wise
Sent: Sat 10/9/2010 7:06 PM
To: yak-list(at)matronics.com (yak-list(at)matronics.com)
Subject: Re: Cowl design and CHT
G'Day Richard,
Years ago I belonged to the Waikerie Gliding Club and used to fly
the Piper Pawnee 260HP tug.
As I never competed in any big gliding comps I undertook the role as
tugmaster.
Now Waikerie can have temps over 40C on some days as the cyl temps
would get pretty hot if not careful.
We found that running a bigger spinner in the summer would
significantly reduce the cyl head temps as the air was possibly
directed over the cyl heads more so than a smaller spinner.
I would imagine that the USA has similar climated conditions as we
have here in Australia.
When flying the 52 or 18T on these hot summer days, one is always
aware of the cyl temps.
The same applies as did the cyl temps on the Pawnee in the summer.
The Yaks with the big spinners run cooler.
Cheers,
Chris
---
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Vic
Joined: 12 Aug 2008 Posts: 116 Location: Southern Bavaria
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Posted: Sun Oct 10, 2010 5:38 pm Post subject: Re: Cowl design and CHT |
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Hello,
another thing to keep in mind : In a radial engine you have different stroke for each piston, in fact several millimeters difference in the M14. So you have different compression ratios as well. This will have some effect on power and temperature for each cylinder. But then, this should concern cylinders with some of the longest strokes to run hotter than the rest. Maybe this fact gets clouded by some other effects still unreflected.
Vic
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dsavarese0812(at)bellsout Guest
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Posted: Mon Oct 11, 2010 7:35 am Post subject: Cowl design and CHT |
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Different stroke lengths-yes. SEVERAL mm - no. Check the specs in the M14 maint manual. Dennis
Sent from my iPhone
On Oct 10, 2010, at 8:38 PM, "Vic" <vicmolnar(at)aol.com> wrote:
Quote: |
Hello,
another thing to keep in mind : In a radial engine you have different stroke for each piston, in fact several millimeters difference in the M14. So you have different compression ratios as well. This will have some effect on power and temperature for each cylinder. But then, this should concern cylinders with some of the longest strokes to run hotter than the rest. Maybe this fact gets clouded by some other effects still unreflected.
Vic
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=315298#315298
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mark.bitterlich(at)navy.m Guest
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Posted: Mon Oct 11, 2010 10:32 am Post subject: Cowl design and CHT |
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I really do not feel qualified to advise you on any of this. If you are asking for my OPINION... well... ok.
The slight hesitation when adding power on final can probably be cured by changing the size of the Acceleration Pump jet. However, I would not do this if you plan on messing with other adjustments. I'd do it last. However, I WOULD mess with this one. It's easy and the change will be felt immediately when you go flying and you are not messing with fuel ratios. Just fuel delivered when the throttle is moved.
I trust Vladimir Yastremski and Dennis and realize fully that both of them have more knowledge and experience on this engine than I probably ever will have.
But if you want to go on .......
Before even thinking of adjusting your carb, make absolutely certain that your timing is correct.
Next... the nice thing about this and most other well build carbs is that you can always put things back to where they were if you are not satisfied with the change you make. The important thing is to be very careful to know where you started and how to get back there should you have to. Be very VERY careful to document everything. I am tempted to advise you to turn the adjustment screw out and count the clicks until it reaches the stop, so you know EXACTLY where it is now. However, having not have done this myself.. and having only read about it... . see what I mean?
It seems that no one on this list has any real first hand experience in making these adjustments. Me included. Several of us have watched people doing it that seem to understand the concepts. Second hand knowledge to be exact.
My YAK-50 will run right up to the red if held in a max performance climb to 5000 feet and I consider it to be adjusted perfectly. Push it over and climb at Vy, and it will stay at high end of green, just as yours seems to.
It's up to you.
Mark
From: Eric Wobschall
Sent: Sun 10/10/2010 8:25 PM
To: yak-list(at)matronics.com
Subject: Re: Cowl design and CHT
Mark:
I had what I considered to be somewhat high CHT on a VERY LOW TIME first run factory engine. This was with factory settings which I was loathe to touch. I'm in Western NY state, so you'd think average settings would cover me. I have checked and tightened various things, including cylinder and supercharger case gland nuts. The temps seem to have crept down. Maybe some of it is break-in, although Jill G. would say break-in is done on a test stand before it sees an airplane. Maybe I've gotten better at managing climb angle, etc.
Rick Volker has been around this plane and felt there was an issue compared with the Sukhois he owned. He also feels spinner and cowl play a big part. as you've read.
I did ring up Vladamir Yastremski (sp?), and he said my temps were well within acceptable limits, and to worry more about low temps. Dennis S. has said about the same thing in the past. Rick suggested test where I climb-out at Vy to 5000 ft. I tried that, and I kept it under 210 C, and then leveled off at max cruise, after which time it stayed in the high green. So that wasn't bad. Now keep in mind this was at 63 degrees ambient at the departure airport (KBQR 752').
About all of these jets: Richard Goode says they all need adjusting, and I think it was Sergei Prolegiev who suggested that I get it out of my head that it left the factory perfectly adjusted. I do have a slight hesitation when I feed power back in on final, but it's not scary. I have all of the different jets, if only I knew what I was doing. I was hoping one or two clockwise clicks on the cruise mixture adjustment would enrichen the mixture enough to make my plane and I happy. I do have great fuel economy, so maybe I'm lean.
Here's my gage and the Yak-UK translated DOSAAF manual I usually go by. Remarks, anyone? -Eric
[img][/img]
On Oct 10, 2010, at 7:32 PM, Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E wrote:
[quote] --> Yak-List message posted by: "Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E" <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)>
No, I am talking about the main mixture jet, which Richard Goode refers to as the "Compensation Jet". Although yes, I have messed with the one you are talking about.
Being perfectly clear here Eric, I was just a spectator. I profess no special knowledge on this darn thing other than: �
1. I have seen where adjusting the accelerator pump jet will cure hesitation on throttle advancement versus just plugging the darn thing, which was the initial cure until smart people figured out you could buy a jet kit and adjust it accordingly. I am VERY familiar with this kind of thing because you run into it a lot adjusting a Holley carb where there are many MANY adjustments for the amount of fuel you dump in when you move the throttle plates.
2. The main jet or "Compensation Jet" has the ability to dramatically change fuel mixture in the mid to high range of engine RPM.
I would very much love to hear Richard Goode go into more detail on how he determines how much change to make based on engine indications. He obviously has way more experience than I do. I have seen it done ONCE... but it worked, in a big way.
I would also like to hear Richard tell me how many clicks on the back of the carb equates to one jet size....if that is the case at all.
Mark
________________________________
From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) on behalf of Eric Wobschall
Sent: Sun 10/10/2010 4:20 PM
To: yak-list(at)matronics.com (yak-list(at)matronics.com)
Subject: Re: Cowl design and CHT
--> Yak-List message posted by: Eric Wobschall <eric(at)buffaloskyline.com (eric(at)buffaloskyline.com)>
Mark, when you say the fuel mixture increase made a big difference, do
you mean the click-stop adjustment on the back of the carburetor?
On Oct 10, 2010, at 3:05 PM, Bitterlich, Mark G CIV Det Cherry Point,
MALS-14 64E wrote:
[quote]--> Yak-List message posted by: "Bitterlich, Mark G CIV Det Cherry
Point, MALS-14 64E" <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)>
Chris,
I run a YAK-18T spinner on my YAK-50. It is one huge spinner. I
have operated the engine with the spinner off and with the spinner
on, and for the one cylinder in my engine that has a probe stuck in
it, the engine ran somewhat cooler with the spinner attached exactly
as you mention. What the other eight were doing, I have no idea.
That said:
I worked with a gent who put in new higher compression pistons and
new cylinders (on a M-14 engine) and another person who was having
very high oil temperature problems (along with cylinder head temps)
on his M-14PF. In both cases, changing the fuel mixture made a
DRAMATIC change in temperatures. I mean, taking it from borderline
RED down into GREEN. The amount of fuel that is dumped into this
engine makes a dramatic change in temps. Spinners can indeed make
an impact, but not nearly as much as fuel.
Another interesting tidbit. One Sukhoi (that I had time watching)
got equipped with a 9 position cylinder head temperature gage (Hubie
Tolson). I wish he had done an exhaustive study (pun intended) but
he mainly just wanted to make sure that he knew what the hottest jug
was. What cylinder ran highest temps changed dramatically from
running it on the ground, to running it in the air, which is
logical. As I remember, hottest on the ground was #2. However in
the air it moved around to #4 or #5 ... I am not sure of that, it
was awhile ago, but anyway it tends to show that the Russians had a
good idea what they were doing when they stuck the probe where they
did.
Lastly, Richard Goode mentioned that the cylinder head temperature
gages we use are far from being dead nuts calibrated units. I've
found that to be true as well (using a calibrated IR unit by Raytec
and also a Thermal IR video unit). What I found from a sampling of
5 spare probes was fairly consistent readings between probes, but a
big difference between gages. I did not even try to calibrate
mine, but instead just recorded where max temp REALLY was and put a
mark on the gage. We tend to put faith in what a gage is telling
us, but that is really far from true. Comparing cylinder head temps
from one aircraft to another (without first running a calibration
check on the instruments you are using) ends up being very much like
comparing apples to oranges.
As an aside, I have only seen one person mess with the jets on these
engines, and interestingly enough it was done exactly like we did on
the drag strip. Make a change, go up and fly it, come back.. talk
about it... make another change, go up and fly it, etc. I doubt if
there is any real "standard" on how to mess with these things other
than to have some idea what you are trying to cure and what
adjustment you should start with, something I wish I knew far more
about, but don't.
Mark Bitterlich
________________________________
From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) on behalf of Chris Wise
Sent: Sat 10/9/2010 7:06 PM
To: yak-list(at)matronics.com (yak-list(at)matronics.com)
Subject: Re: Cowl design and CHT
G'Day Richard,
Years ago I belonged to the Waikerie Gliding Club and used to fly
the Piper Pawnee 260HP tug.
As I never competed in any big gliding comps I undertook the role as
tugmaster.
Now Waikerie can have temps over 40C on some days as the cyl temps
would get pretty hot if not careful.
We found that running a bigger spinner in the summer would
significantly reduce the cyl head temps as the air was possibly
directed over the cyl heads more so than a smaller spinner.
I would imagine that the USA has similar climated conditions as we
have here in Australia.
When flying the 52 or 18T on these hot summer days, one is always
aware of the cyl temps.
The same applies as did the cyl temps on the Pawnee in the summer.
The Yaks with the big spinners run cooler.
Cheers,
Chris
---
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dsavarese0812(at)bellsout Guest
|
Posted: Mon Oct 11, 2010 10:40 am Post subject: Cowl design and CHT |
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M14 Stroke:
#4 - 130.00 mm
#3 and #5 130.15 mm
#2 and #6 130.23 mm
#8 and #9 130.39 mm
#1 and #7 131.25 mm
Largest difference #4 to #1 or #7 = 1.25 mm
Dennis
[quote] ---
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radiopicture
Joined: 23 Jun 2008 Posts: 263
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Posted: Mon Oct 11, 2010 2:38 pm Post subject: Cowl design and CHT |
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|
Thanks, Mark. Plugging it into the formula.
On Oct 11, 2010, at 2:26 PM, Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E wrote:
[quote] I really do not feel qualified to advise you on any of this. If you are asking for my OPINION... well... ok.
The slight hesitation when adding power on final can probably be cured by changing the size of the Acceleration Pump jet. However, I would not do this if you plan on messing with other adjustments. I'd do it last. However, I WOULD mess with this one. It's easy and the change will be felt immediately when you go flying and you are not messing with fuel ratios. Just fuel delivered when the throttle is moved.
I trust Vladimir Yastremski and Dennis and realize fully that both of them have more knowledge and experience on this engine than I probably ever will have.
But if you want to go on .......
Before even thinking of adjusting your carb, make absolutely certain that your timing is correct.
Next... the nice thing about this and most other well build carbs is that you can always put things back to where they were if you are not satisfied with the change you make. The important thing is to be very careful to know where you started and how to get back there should you have to. Be very VERY careful to document everything. I am tempted to advise you to turn the adjustment screw out and count the clicks until it reaches the stop, so you know EXACTLY where it is now. However, having not have done this myself.. and having only read about it... . see what I mean?
It seems that no one on this list has any real first hand experience in making these adjustments. Me included. Several of us have watched people doing it that seem to understand the concepts. Second hand knowledge to be exact.
My YAK-50 will run right up to the red if held in a max performance climb to 5000 feet and I consider it to be adjusted perfectly. Push it over and climb at Vy, and it will stay at high end of green, just as yours seems to.
It's up to you.
Mark
From: Eric Wobschall
Sent: Sun 10/10/2010 8:25 PM
To: yak-list(at)matronics.com (yak-list(at)matronics.com)
Subject: Re: Cowl design and CHT
Mark:
I had what I considered to be somewhat high CHT on a VERY LOW TIME first run factory engine. This was with factory settings which I was loathe to touch. I'm in Western NY state, so you'd think average settings would cover me. I have checked and tightened various things, including cylinder and supercharger case gland nuts. The temps seem to have crept down. Maybe some of it is break-in, although Jill G. would say break-in is done on a test stand before it sees an airplane. Maybe I've gotten better at managing climb angle, etc.
Rick Volker has been around this plane and felt there was an issue compared with the Sukhois he owned. He also feels spinner and cowl play a big part. as you've read.
I did ring up Vladamir Yastremski (sp?), and he said my temps were well within acceptable limits, and to worry more about low temps. Dennis S. has said about the same thing in the past. Rick suggested test where I climb-out at Vy to 5000 ft. I tried that, and I kept it under 210 C, and then leveled off at max cruise, after which time it stayed in the high green. So that wasn't bad. Now keep in mind this was at 63 degrees ambient at the departure airport (KBQR 752').
About all of these jets: Richard Goode says they all need adjusting, and I think it was Sergei Prolegiev who suggested that I get it out of my head that it left the factory perfectly adjusted. I do have a slight hesitation when I feed power back in on final, but it's not scary. I have all of the different jets, if only I knew what I was doing. I was hoping one or two clockwise clicks on the cruise mixture adjustment would enrichen the mixture enough to make my plane and I happy. I do have great fuel economy, so maybe I'm lean.
Here's my gage and the Yak-UK translated DOSAAF manual I usually go by. Remarks, anyone? -Eric
[img][/img]
On Oct 10, 2010, at 7:32 PM, Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E wrote:
[quote] --> Yak-List message posted by: "Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E" <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)>
No, I am talking about the main mixture jet, which Richard Goode refers to as the "Compensation Jet". Although yes, I have messed with the one you are talking about.
Being perfectly clear here Eric, I was just a spectator. I profess no special knowledge on this darn thing other than:
1. I have seen where adjusting the accelerator pump jet will cure hesitation on throttle advancement versus just plugging the darn thing, which was the initial cure until smart people figured out you could buy a jet kit and adjust it accordingly. I am VERY familiar with this kind of thing because you run into it a lot adjusting a Holley carb where there are many MANY adjustments for the amount of fuel you dump in when you move the throttle plates.
2. The main jet or "Compensation Jet" has the ability to dramatically change fuel mixture in the mid to high range of engine RPM.
I would very much love to hear Richard Goode go into more detail on how he determines how much change to make based on engine indications. He obviously has way more experience than I do. I have seen it done ONCE... but it worked, in a big way.
I would also like to hear Richard tell me how many clicks on the back of the carb equates to one jet size....if that is the case at all.
Mark
________________________________
From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) on behalf of Eric Wobschall
Sent: Sun 10/10/2010 4:20 PM
To: yak-list(at)matronics.com (yak-list(at)matronics.com)
Subject: Re: Cowl design and CHT
--> Yak-List message posted by: Eric Wobschall <eric(at)buffaloskyline.com (eric(at)buffaloskyline.com)>
Mark, when you say the fuel mixture increase made a big difference, do
you mean the click-stop adjustment on the back of the carburetor?
On Oct 10, 2010, at 3:05 PM, Bitterlich, Mark G CIV Det Cherry Point,
MALS-14 64E wrote:
[quote]--> Yak-List message posted by: "Bitterlich, Mark G CIV Det Cherry
Point, MALS-14 64E" <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)>
Chris,
I run a YAK-18T spinner on my YAK-50. It is one huge spinner. I
have operated the engine with the spinner off and with the spinner
on, and for the one cylinder in my engine that has a probe stuck in
it, the engine ran somewhat cooler with the spinner attached exactly
as you mention. What the other eight were doing, I have no idea.
That said:
I worked with a gent who put in new higher compression pistons and
new cylinders (on a M-14 engine) and another person who was having
very high oil temperature problems (along with cylinder head temps)
on his M-14PF. In both cases, changing the fuel mixture made a
DRAMATIC change in temperatures. I mean, taking it from borderline
RED down into GREEN. The amount of fuel that is dumped into this
engine makes a dramatic change in temps. Spinners can indeed make
an impact, but not nearly as much as fuel.
Another interesting tidbit. One Sukhoi (that I had time watching)
got equipped with a 9 position cylinder head temperature gage (Hubie
Tolson). I wish he had done an exhaustive study (pun intended) but
he mainly just wanted to make sure that he knew what the hottest jug
was. What cylinder ran highest temps changed dramatically from
running it on the ground, to running it in the air, which is
logical. As I remember, hottest on the ground was #2. However in
the air it moved around to #4 or #5 ... I am not sure of that, it
was awhile ago, but anyway it tends to show that the Russians had a
good idea what they were doing when they stuck the probe where they
did.
Lastly, Richard Goode mentioned that the cylinder head temperature
gages we use are far from being dead nuts calibrated units. I've
found that to be true as well (using a calibrated IR unit by Raytec
and also a Thermal IR video unit). What I found from a sampling of
5 spare probes was fairly consistent readings between probes, but a
big difference between gages. I did not even try to calibrate
mine, but instead just recorded where max temp REALLY was and put a
mark on the gage. We tend to put faith in what a gage is telling
us, but that is really far from true. Comparing cylinder head temps
from one aircraft to another (without first running a calibration
check on the instruments you are using) ends up being very much like
comparing apples to oranges.
As an aside, I have only seen one person mess with the jets on these
engines, and interestingly enough it was done exactly like we did on
the drag strip. Make a change, go up and fly it, come back.. talk
about it... make another change, go up and fly it, etc. I doubt if
there is any real "standard" on how to mess with these things other
than to have some idea what you are trying to cure and what
adjustment you should start with, something I wish I knew far more
about, but don't.
Mark Bitterlich
________________________________
From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) on behalf of Chris Wise
Sent: Sat 10/9/2010 7:06 PM
To: yak-list(at)matronics.com (yak-list(at)matronics.com)
Subject: Re: Cowl design and CHT
G'Day Richard,
Years ago I belonged to the Waikerie Gliding Club and used to fly
the Piper Pawnee 260HP tug.
As I never competed in any big gliding comps I undertook the role as
tugmaster.
Now Waikerie can have temps over 40C on some days as the cyl temps
would get pretty hot if not careful.
We found that running a bigger spinner in the summer would
significantly reduce the cyl head temps as the air was possibly
directed over the cyl heads more so than a smaller spinner.
I would imagine that the USA has similar climated conditions as we
have here in Australia.
When flying the 52 or 18T on these hot summer days, one is always
aware of the cyl temps.
The same applies as did the cyl temps on the Pawnee in the summer.
The Yaks with the big spinners run cooler.
Cheers,
Chris
---
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