Matronics Email Lists :: View topic - Engine roughness, as in stops. starts. stops. starts.

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Engine roughness, as in stops. starts. stops. starts.
Goto page 1, 2 Next

Matronics Email Lists Forum Index -> Yak-List

View previous topic :: View next topic

Author Message

mark.bitterlich(at)navy.m
Guest

Posted: Fri May 29, 2015 6:59 am Post subject: Engine roughness, as in stops. starts. stops. starts.

Might as well add my 2 cents.   First of all, I totally concur with Richard Goode, not only because he has been around these aircraft longer than most anyone else on this list, but also because I have experienced the exact same symptoms troubleshooting a YAK-52 just a few months ago.  



Very likely NOT the carb.   And this is not meant as sarcasm, but after some "mechs" mess around with it for a while it might very well end up being that as well.  Very few people know how to adjust these pressure carbs properly and there is much more to it than turning the "screw" on the outside.   Of course there is nothing like "doing" to help in learning, as long as it is on your aircraft and not mine please.  What I am saying here is that messing around with the carb should be LAST on anyone's list and never first.  Also it is the nature of pressure carbs that if you adjust one thing, it impacts another.  Just had a Bendix PS-7BD rebuilt and flowed ($3000 by the way) and while not Russian, the theory is the same and worth reading about.  



There is a very simple test to run here.  Go up and fly it one more time and just simply fly it until it starts doing this again, and then switch off one mag and then the other to see if it then STOPS doing it or gets much worse on one.   It is very  unusual for both mags to have something go bad with them at the same time (thankfully).   STRONGLY recommend this before applying fingers or tools to the carb.   



The problem with the coils is legendary.  If you own one of these aircraft it is not a matter of "if" you will have a coil go bad, but when.   Other things can cause the coil to over-heat faster and these range from wide gaps on spark plugs, to misadjusted points "or dwell" as mentioned.  Also, I have seen the point assembly actually crack leading to erratic ignition (you mentioned that one yourself).  Points will not usually come out of adjustment through normal use enough to cause what you are experiencing, but if they are cracked and flexing they can cause these exact symptoms too.  



I have had two personal experiences with mag issues on my own aircraft.  In one case, the internal gearing in the mag (M9F) let go, and the engine just STOPPED.   Ernie (in another message) mentioned that this should not happen should it?   Well, that is what we are all taught, but as it turns out it is not necessarily accurate.   I did not time how many seconds it just STOPPED, but it was enough time for me to think: "Oh crap, I am going to have to land this thing on the freaking OUTER BANKS!  Should I go in gear up or down?".  And then it came back running rougher than blazes.  I tried the mag switch, and it ran on one mag perfectly and on the other it just stopped.  So why did that happen?  It should not have.   But it did.  Lots of "might be maybe" theory, but honestly I do not know.  



Second time was a mag coil.  Pretty much exactly what you are talking about here.   Again, simply switching between mags in flight isolated the problem very quickly.   Why did it impact engine performance on both?  Well, all I can think of is a spark plug firing way in advance.   In my mind, only three things can happen with ignition.  It doesn't work at all, it fires early, or it fires late.  Not working at all would not make the engine cough and gag, UNLESS you had a problem with the OTHER ignition set that you didn't know about (bad plug, etc.)  If it fired late, it would not matter at all.  But if it fired early... way early, as the piston was coming up on the compression stroke ..... some weird stuff would happen, bad detonation and engine coughing and puking being one.   So that is my "theory".  



If this test is performed in flight and it does it again on EITHER MAG, then the next step is a compression test.   But really, you need to fly it one more time. 



Mark





--

cjpilot710(at)aol.com
Guest

Posted: Fri May 29, 2015 8:12 am Post subject: Engine roughness, as in stops. starts. stops. starts.

I think Mark is right on the money here.

 Jim "Pappy" Goolsby

  

  In a message dated 5/29/2015 11:00:01 A.M. Eastern Daylight Time,  mark.bitterlich(at)navy.mil writes:

 [quote]-->    Yak-List message posted by: "Bitterlich, Mark G CIV NAVAIR, WD"    <mark.bitterlich(at)navy.mil>



Might as well add my 2    cents.   First of all, I totally concur with Richard Goode, not only    because he has been around these aircraft longer than most anyone else on this    list, but also because I have experienced the exact same symptoms    troubleshooting a YAK-52 just a few months ago.  



Very likely NOT    the carb.   And this is not meant as sarcasm, but after some "mechs"    mess around with it for a while it might very well end up being that as    well.  Very few people know how to adjust these pressure carbs properly    and there is much more to it than turning the "screw" on the    outside.   Of course there is nothing like "doing" to help in    learning, as long as it is on your aircraft and not mine please.  What I    am saying here is that messing around with the carb should be LAST on anyone's    list and never first.  Also it is the nature of pressure carbs that if    you adjust one thing, it impacts another.  Just had a Bendix PS-7BD    rebuilt and flowed ($3000 by the way) and while not Russian, the theory is the    same and worth reading about.  



There is a very simple test to run    here.  Go up and fly it one more time and just simply fly it until it    starts doing this again, and then switch off one mag and then the other to see    if it then STOPS doing it or gets much worse on one.   It is    very  unusual for both mags to have something go bad with them at the    same time (thankfully).   STRONGLY recommend this before applying    fingers or tools to the carb.   



The problem with the coils    is legendary.  If you own one of these aircraft it is not a matter of    "if" you will have a coil go bad, but when.   Other things can cause    the coil to over-heat faster and these range from wide gaps on spark plugs, to    misadjusted points "or dwell" as mentioned.  Also, I have seen the point    assembly actually crack leading to erratic ignition (you mentioned that one    yourself).  Points will not usually come out of adjustment through normal    use enough to cause what you are experiencing, but if they are cracked and    flexing they can cause these exact symptoms too.  



I have had two    personal experiences with mag issues on my own aircraft.  In one case,    the internal gearing in the mag (M9F) let go, and the engine just    STOPPED.   Ernie (in another message) mentioned that this should not    happen should it?   Well, that is what we are all taught, but as it    turns out it is not necessarily accurate.   I did not time how many    seconds it just STOPPED, but it was enough time for me to think: "Oh crap, I    am going to have to land this thing on the freaking OUTER BANKS!  Should    I go in gear up or down?".  And then it came back running rougher than    blazes.  I tried the mag switch, and it ran on one mag perfectly and on    the other it just stopped.  So why did that happen?  It should not    have.   But it did.  Lots of "might be maybe" theory, but    honestly I do not know.  



Second time was a mag coil.  Pretty    much exactly what you are talking about here.   Again, simply    switching between mags in flight isolated the problem very    quickly.   Why did it impact engine performance on both?  Well,    all I can think of is a spark plug firing way in advance.   In my    mind, only three things can happen with ignition.  It doesn't work at    all, it fires early, or it fires late.  Not working at all would not make    the engine cough and gag, UNLESS you had a problem with the OTHER ignition set    that you didn't know about (bad plug, etc.)  If it fired late, it would    not matter at all.  But if it fired early... way early, as the piston was    coming up on the compression stroke ..... some weird stuff would happen, bad    detonation and engine coughing and puking being one.   So that is my    "theory".  



If this test is performed in flight and it does it    again on EITHER MAG, then the next step is a compression test.   But    really, you need to fly it one more time.    



Mark





--

jan.mevis(at)informavia.b
Guest

Posted: Sun May 31, 2015 9:05 am Post subject: Engine roughness, as in stops. starts. stops. starts.

Massive discharge with the heat induced break down of the capacitor?

I don't understand this, can you explain please?

Jan

On 31/05/15 18:48, "Roger Kemp" <f16viperdoc(at)me.com> wrote:

 	  Quote: 	

As explained by the Lithuanian engineers the massive discharge with the

heat induced break down of the capacitor in the coil results in arcing in

the distributor cap so that discharge flows / jumps to the next cylinder

in line on the intake stroke. With the intake valve open when that

aberrant discharge arrives the spark will consume the supercharger

contents. The backfire is most likely through the carb when the charge is

consumed. 

The pilots of the  aircraft in formation with me said they saw a sudden

belch of black smoke from under the chin of my bird. I felt the

hesitation as well as saw the momentary hesitation of the prop slowing.

Then the engine picked back up like nothing occurred. Have had that

happen twice since owning my 52. Did an airborne mag check the second

time with the engine quitting on selection of the #1 mag. In both cases

changing the mag coils resolved the problem.

Litaurus and Termikus are the bearers of that tidbit of info. Made sense

to me then and now.

Doc

Sent from my iPad

> On May 31, 2015, at 3:38 AM, JL2A <info(at)flyingwarbirds.com.au> wrote:

> 

> 

> 

> I'm with Egon, getting an engine anywhere near 200°C on the ground is

>very hard on them, let alone 250°C. Without the proper cooling airflow

>wrapping around the cylinders they are getting unevenly hot,  with

>hotspots that may exceed the temperature of where the thermocouple is

>placed.

> 

> I've got to ask - what are we talking about lighting the whole

>supercharger 'charge' on fire?

> 

> Do they mean the spark is so advanced it lights off way early and the

>flame front travels backwards through the induction system? Is this even

>physically at anything above starting RPM?

> 

> 

> 

> 

> Read this topic online here:

> 

> http://forums.matronics.com/viewtopic.php?p=442829#442829

> 

> 

> 

> 

> 

> 

> 

> 

> 

>

jblake207(at)comcast.net
Guest

Posted: Sun May 31, 2015 4:03 pm Post subject: Engine roughness, as in stops. starts. stops. starts.

Doc, does that spinal infusion come with a little umbrella and slice of lime?  JB

Sent from my Verizon Wireless 4G LTE DROID

Roger Kemp <f16viperdoc(at)me.com> wrote:

 	  Quote: 	

Jan,

I personally do not know what is breaking down in the coil between the primary and secondary windings that causes the aberrant high voltage discharge. I do not know how the Russians build their secondary winding pies or how they insulate them. Is it an internal resistor that fails, is it the waxed cardboard insulation or the break down of the rubberized insulation that results in the current leakage. Is it internal heat build up and air bubble expansion that allows internal arching I do not know. I just know I was told there is a breakdown and that results in an aberrant spark that causes an impressive internal backfire with momentary engine pause that causes an eye opening experience. 

I personally accepted what Litaurus and Termikus said because it made sense it its simplified term. It is kind of like me telling a cancer patient suffering from intractable pain that I can put a catheter in their subarachnoid space in their spinal canal that infuses micro-milliliters of narcotic and local anesthetic into the cerebrospinal fluid with the tip of the catheter over the dermatonal  segment that corresponds to their afferent pain input into level three and seven of the Rexed Lamina  in the posterior horn of the cord. Using that combination we will be blocking nocioceptive and neuropathic pain. 

All they care about is their pain going to be better controlled and they are not going to be gorked on drugs in their last months or days. Litaurus's explanation fits the simplified answer. All I wanted was does changing the coil out stop the problem. It did in my case. I now have two spare coils sitting in my spares cabinet. 

Doc

Sent from my iPad

> On May 31, 2015, at 11:48 AM, Roger Kemp <f16viperdoc(at)me.com> wrote:

> 

> 

> 

> As explained by the Lithuanian engineers the massive discharge with the heat induced break down of the capacitor in the coil results in arcing in the distributor cap so that discharge flows / jumps to the next cylinder in line on the intake stroke. With the intake valve open when that aberrant discharge arrives the spark will consume the supercharger contents. The backfire is most likely through the carb when the charge is consumed. 

> The pilots of the  aircraft in formation with me said they saw a sudden belch of black smoke from under the chin of my bird. I felt the hesitation as well as saw the momentary hesitation of the prop slowing. Then the engine picked back up like nothing occurred. Have had that happen twice since owning my 52. Did an airborne mag check the second time with the engine quitting on selection of the #1 mag. In both cases changing the mag coils resolved the problem.

> Litaurus and Termikus are the bearers of that tidbit of info. Made sense to me then and now. 

> Doc

> 

> Sent from my iPad

> 

>> On May 31, 2015, at 3:38 AM, JL2A <info(at)flyingwarbirds.com.au> wrote:

>> 

>> 

>> 

>> I'm with Egon, getting an engine anywhere near 200Â°C on the ground is very hard on them, let alone 250Â°C. Without the proper cooling airflow wrapping around the cylinders they are getting unevenly hot,  with hotspots that may exceed the temperature of where the thermocouple is placed.

>> 

>> I've got to ask - what are we talking about lighting the whole supercharger 'charge' on fire?

>> 

>> Do they mean the spark is so advanced it lights off way early and the flame front travels backwards through the induction system? Is this even physically at anything above starting RPM?

>> 

>> 

>> 

>> 

>> Read this topic online here:

>> 

>> http://forums.matronics.com/viewtopic.php?p=442829#442829

> 

> 

> 

> 

> 

_-============================================================

_-=          - The Yak-List Email Forum -

_-= Use the Matronics List Features Navigator to browse

_-= the many List utilities such as List Un/Subscription,

_-= Archive Search & Download, 7-Day Browse, Chat, FAQ,

_-= Photoshare, and much much more:

_-=

_-=   --> http://www.matronics.com/Navigator?Yak-List

_-=

_-============================================================

_-=               - MATRONICS WEB FORUMS -

_-= Same great content also available via the Web Forums!

_-=

_-=   --> http://forums.matronics.com

_-=

_-============================================================

_-=             - List Contribution Web Site -

_-=  Thank you for your generous support!

_-=                              -Matt Dralle, List Admin.

_-=   --> http://www.matronics.com/contribution

_-============================================================

jan.mevis(at)informavia.b
Guest

Posted: Sun May 31, 2015 9:07 pm Post subject: Engine roughness, as in stops. starts. stops. starts.

Ok Doc, it's simple curiosity.

The people from Termikas are very knowledgeable. I've been there several

times.



Thanks,



Jan



On 31/05/15 22:21, "Roger Kemp" <f16viperdoc(at)me.com> wrote:



 	  Quote: 	
		  



Jan,

I personally do not know what is breaking down in the coil between the

primary and secondary windings that causes the aberrant high voltage

discharge. I do not know how the Russians build their secondary winding

pies or how they insulate them. Is it an internal resistor that fails, is

it the waxed cardboard insulation or the break down of the rubberized

insulation that results in the current leakage. Is it internal heat build

up and air bubble expansion that allows internal arching I do not know. I

just know I was told there is a breakdown and that results in an aberrant

spark that causes an impressive internal backfire with momentary engine

pause that causes an eye opening experience.

I personally accepted what Litaurus and Termikus said because it made

sense it its simplified term. It is kind of like me telling a cancer

patient suffering from intractable pain that I can put a catheter in

their subarachnoid space in their spinal canal that infuses

micro-milliliters of narcotic and local anesthetic into the cerebrospinal

fluid with the tip of the catheter over the dermatonal  segment that

corresponds to their afferent pain input into level three and seven of

the Rexed Lamina  in the posterior horn of the cord. Using that

combination we will be blocking nocioceptive and neuropathic pain.

All they care about is their pain going to be better controlled and they

are not going to be gorked on drugs in their last months or days.

Litaurus's explanation fits the simplified answer. All I wanted was does

changing the coil out stop the problem. It did in my case. I now have two

spare coils sitting in my spares cabinet.

Doc



Sent from my iPad



> On May 31, 2015, at 11:48 AM, Roger Kemp <f16viperdoc(at)me.com> wrote:

> 

> 

> 

> As explained by the Lithuanian engineers the massive discharge with the

>heat induced break down of the capacitor in the coil results in arcing

>in the distributor cap so that discharge flows / jumps to the next

>cylinder in line on the intake stroke. With the intake valve open when

>that aberrant discharge arrives the spark will consume the supercharger

>contents. The backfire is most likely through the carb when the charge

>is consumed. 

> The pilots of the  aircraft in formation with me said they saw a sudden

>belch of black smoke from under the chin of my bird. I felt the

>hesitation as well as saw the momentary hesitation of the prop slowing.

>Then the engine picked back up like nothing occurred. Have had that

>happen twice since owning my 52. Did an airborne mag check the second

>time with the engine quitting on selection of the #1 mag. In both cases

>changing the mag coils resolved the problem.

> Litaurus and Termikus are the bearers of that tidbit of info. Made

>sense to me then and now.

> Doc

> 

> Sent from my iPad

> 

>> On May 31, 2015, at 3:38 AM, JL2A <info(at)flyingwarbirds.com.au> wrote:

>> 

>> 

>> 

>> I'm with Egon, getting an engine anywhere near 200°C on the ground is

>>very hard on them, let alone 250°C. Without the proper cooling airflow

>>wrapping around the cylinders they are getting unevenly hot,  with

>>hotspots that may exceed the temperature of where the thermocouple is

>>placed.

>> 

>> I've got to ask - what are we talking about lighting the whole

>>supercharger 'charge' on fire?

>> 

>> Do they mean the spark is so advanced it lights off way early and the

>>flame front travels backwards through the induction system? Is this

>>even physically at anything above starting RPM?

>> 

>> 

>> 

>> 

>> Read this topic online here:

>> 

>> http://forums.matronics.com/viewtopic.php?p=442829#442829

> 

> 

> 

> 

>

mark.bitterlich(at)navy.m
Guest

Posted: Mon Jun 01, 2015 7:01 am Post subject: Engine roughness, as in stops. starts. stops. starts.

Well..  Doc, I think there might have been a misunderstanding somewhere along the line.   This is not a reasonable explanation.  



--

mark.bitterlich(at)navy.m
Guest

Posted: Mon Jun 01, 2015 8:00 am Post subject: Engine roughness, as in stops. starts. stops. starts.

What  should be keep in mind here is that Doc is actually talking about hear-say information and that he is not an expert in this particular field.  Medicine yes.  High voltage coil theory not necessarily.  



A break down between the primary and secondary winding of a coil will never cause a high voltage discharge.   A break down occurs when the primary shorts to the secondary.  When this happens, the primary winding can no longer produce the magnetic field that is necessary to induce the high voltage in the secondary.    So a break down in the coil being an explanation for this event is pretty much out of the question.  Once coil winding insulation breaks down there is a pretty much a flash-over and the short circuit remains permanent.  I.E.  It USUALLY stops working, it does not become intermittent.    Realize that the failure mode of these Mag Coils is common and has occurred multiple times across platforms.   So it is a USUAL failure mode and not a rare event.  



Something you also need to be aware of Doc is that you are talking to a gentleman who helped design and manufacture a replacement coil for the Russian design and is intimately familiar with how it works.  To a lesser degree, so am I.   I respect Jan's knowledge in this field and so should anyone else speaking to him.  He has been to all these places, he has been to Russia, he has talked face to face with many engineers about the design of this particular part.  I consider anyone who has made replacement coils for this mag to be an expert.     



Energy from the high voltage system in the magneto increasing to the point where it "flashes" across to an adjacent point internal to the mag cap is also very unlikely because of two things: 



1.  High energy goes to the path of least resistance.  An air gap represents a huge amount of resistance.  It can happen, but not likely because of an INCREASE in high voltage output, simply because there is no FAILURE mode that can cause that.  So flash over is not happening.  



2.  If it were to happen, there would be a carbon trail showing that it happened in the cap.  Inspection has proven that not to be the case.  



Investigation of failed coils has been undertaken by a number of people, including Jill and gang at M14P.com (as well as Jan Mevis).   M14P's determination was that in many cases the internal CAPACITOR in the coil had failed.  One then has to ask what that capacitor does, and what could be the by-product of it failing.  



Anyone who has driven an older model car with a distributor, points, CAPACITOR (also called a CONDENSOR)  and rotor and external coil can pretty  much understand what is going on with a mag.  The only difference is that the external high voltage coil in a CAR has the primary driven by (usually) 12 Volts DC, whereas a mag uses permanent magnets to generate a magnetic field instead of a battery to produce the same effect in an autotransformer.  This design feature allows it to produce spark energy with no external power input, which is the whole idea.  The engine runs even with a total electrical failure.  It is however a limitation as well, as it is hard to match the new high energy designs found in totals designs.  Aircraft mags don't put out anything near what an MSD ignition can, which is why I designed a method to put that exact system into these aircraft and offered the idea to anyone who wanted to run with it.  By the way, Jan Mevis prototyped that installation design.  



But we come back to the capacitor.  Caps do have a failure mode where they can change value over time and with heat.  What does the cap do?  



Quote: http://en.wikipedia.org/wiki/Ignition_system 



The capacitor has two functions. Its main function is to form a series resonant circuit with the ignition coil. During resonance, energy is repeatedly transferred to the secondary side until the energy is exhausted.[2] As a result of this resonance the duration of the spark is sustained and so implements a good flame front in the air/fuel mixture. The capacitor, by default minimizes arcing at the contacts at the point of opening. This reduces contact burning and maximizes point life. 

Unquote: 



The real clue as to how it works is this statement:  "Its main function is to form a series resonant circuit with the ignition coil"  If you understand "resonance" in Alternating Current (AC) theory, the light bulb should come on about now.  



If anyone would like this email to become another page longer, we can discuss the fact that with a failed condenser now the coil is instantly energized producing a moving magnetic field, which induces energy into the secondary when the points OPEN *AND* CLOSE.  Although much weaker, it then would be possible to get a plug to fire when it never was meant to fire.  And that could cause bad things to happen.  As in  "way too advanced" as I mentioned earlier in another email (which is why I suspected this might be happening).  This event would cause the engine to lose a huge amount of power, all at once and would indeed cause big puffs of black smoke out of the exhaust.  



On a side note, igniting the fuel mixture in a Supercharger (usually called a Supercharger Backfire) is a really REALLY bad thing.  On race cars, this normally causes the blower to literally be blown right off the top of the motor.  Given that our blowers are not running nearly that kind of pressure, it still would be the kind of event that would get attention, with flames and smoke coming back out of the carb.  I do not think that is happening in the discussed event.  



Mark



.   



--

mark.bitterlich(at)navy.m
Guest

Posted: Mon Jun 01, 2015 12:49 pm Post subject: Engine roughness, as in stops. starts. stops. starts.

The problem being discussed was focused on a primary to secondary short.   Not the primary failing open.



That said, yes... you are correct.   If the points were closed, and the flux field was at maximum, and then suddenly the primary opened, there would indeed be a single spark discharge.



At that point, the coil primary would remain open, and that mag would then be totally dead.   High Voltage coil windings do not open and then fix themselves and start working again.



The rest of the thread explained what component does exhibit those tendencies and what such a failure would cause.

--

wlannon(at)shaw.ca
Guest

Posted: Mon Jun 01, 2015 6:31 pm Post subject: Engine roughness, as in stops. starts. stops. starts.

Mark;



I have been trying to get my head around this theory of a "massive 

discharge" etc. but have been too busy of late to sit down and think it 

through.   So far it just doesn't compute.

I have had only one coil failure in forty years of playing with radial 

engines.   That was in a Harvard with Bosch mags.  That mag simply quit 

working, not intermittent, no bangs or whatever just simply and permanently 

dead.

Right now dead tired and another full day tomorrow.



Cheers;

Walt

--

jan.mevis(at)informavia.b
Guest

Posted: Thu Jun 04, 2015 3:24 am Post subject: Engine roughness, as in stops. starts. stops. starts.

The timing is carefully checked and synced between left and right.

But I have an M14R 450 PS engine. Fuel consumption is about twice the

consumption of a standard engine.

I measure the temperature of all the cylinders, and keep these data for

trend evolution.

Since employing the MSD, temperature is 10 to 15 degrees centigrades

higher per cylinder.

I can easily switch back to a coil system (one hour of work) and then the

temperature is "normal".

Jan

On 04/06/15 12:13, "JL2A" <info(at)flyingwarbirds.com.au> wrote:

 	  Quote: 	

> Since then, I measure substantially higher CHT on all cylinders so

>better combustion.

Careful! I would have thought having substantially higher CHTs after

changing the ignition system would indicate you've got the timing wrong.

A normally set up factory system is going to light most of the fuel/air,

a stronger spark might help light a little more especially if very lean

of peak, but a spark is a spark, and we've got two per jug in these.

High CHTs are NOT an indicator of 'better' combustion! Unless you mean

before your engine didn't run and now it does!  

Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=442983#442983

mark.bitterlich(at)navy.m
Guest

Posted: Thu Jun 04, 2015 9:12 am Post subject: Engine roughness, as in stops. starts. stops. starts.

All things being equal I would agree.   However all things are not.... not really.    



A gross change in flame propagation will indeed change CHT.    Typical M-14's and especially the M-9R ... are always run extremely rich.  In fact the fuel is actually used for cooling and keeps the CHT in range.  So you're dumping a lot of unburnt fuel out the exhaust on a regular basis, and this is necessary condition.  If you tune for "perfect combustion" on these engines, the CHT will head to the moon.   So when you introduce a spark like an MSD produces... it is not just a spark, it is an extremely long duration event, which turns more of that fuel into energy, and the result is more power produced, but also less cooling, since more of that excess fuel is now turned into power.  



Concur that timing changes also impact CHT of course.. no disagreement.      



Jan is running an M-9R (are you familiar with that particular engine?  I ask because very few people even know they exist.  Jan had at one time a movie of an engine start.   Starting and running on the stock mag it was spitting and barking as it warmed up.  He then switched the MSD system in and the engine idled perfectly ... clock like in fact.... when dead cold.     



Jan's mech is also EXTREMELY proficient with these engines, and the timing is dead on.  



So actually Jan knows exactly where-of he speaks.  



Mark

--

Rob Rowe

Joined: 10 Jan 2006
Posts: 124
Location: Berkshire, UK

Posted: Thu Jun 25, 2015 8:01 am Post subject: Re: Engine roughness, as in stops. starts. stops. starts.

Iâ€™m a little late to this discussion about magneto erratic failure when hot, but hereâ€™s my 5 pence input for what itâ€™s worth.



A few years back I assisted in the commissioning of a magneto tester and in so doing ended up researching the nearly 100 year old information on this topic and discovered just how nuanced it is. Essentially this technology reached its peak interest post (Great) war, with research paper references going back to the 1860s!



For someone who reads a lot of technology papers itâ€™s a humble reminder that latter day technical research is not the only source of learning or innovation.



Iâ€™ve provided links to the research papers below, but first Iâ€™ll summarise some thoughts that MAY be a scenario for our YAK mag failure experiences;



1 â€“ To create a reliable spark (at least across an air gap on a magneto tester) a â€˜teaserâ€™ electrode is needed to create an ion rich area to help allow the spark to form. If this is not present then a spark may form irregularly depending on ion availability.

Point #1 - an ion rich environment is conducive to flash-over



2 â€“ With increasing height air density reduces, as does its electrical insulation properties.

Point #2 â€“ as height increases the voltage required for a flash-over inside the magneto reduces



3 â€“ A leaner cylinder mixture increases the voltage required for a spark-plug to fire 

Point #3 â€“ leaning the aircraft in cruise increases the magneto voltage required for spark-plug operation



4 â€“ Magneto impedance (as weâ€™re referring to its AC properties) is related more to inductance than resistance with rising frequency (increasing engine RPM).

Point #4 â€“ in the cruise with reduced RPM then magneto resistive heating may be more apparent, aggravated by #3 where the cruise also requires a higher magneto energy level to be generated



From the above we might infer that when in the cruise at height the magnetos are at their mostly likely to heat up and are more vulnerable to air insulation break-down.



Now put this in conjunction with Jan Mevisâ€™s observation, that the variable construction quality of the winding insulation (with heat) can lead to any trapped moisture vaporising and breaking down the insulation across weak points.



Then such a break-down would create an ion rich environment around the windings that could trigger premature & successive flash overs to other weak points impacting engine operation - in much the same way as lightning storm ions from an initial strike may often lead to the triggering of multiple events. In this case each event progressively weakens the secondary insulation, making it more likely to fail subsequently when subjected to similar conditions.



Now this is all subject to a LOT of contributory variables, hence why such a perfect (ion) storm failure mode might be a highly unpredictable initial occurrence & subject to small environmental changes that might push a marginally functioning magneto finally over the edge.



Anyway so much for my conjecture, here are the research paper links â€¦ enjoy!



Characteristics of  High Tension Magnetos (1920) â€“ NACA #58

http://naca.central.cranfield.ac.uk/reports/1920/naca-report-58.pdf



Simplified Theory of the Magneto (1923) â€“ NACA #123

http://naca.central.cranfield.ac.uk/reports/1923/naca-report-123.pdf



The Sparking Voltage of Spark Plugs (1925) â€“ NACA #202

http://naca.central.cranfield.ac.uk/reports/1925/naca-report-202.pdf

Brgds, Rob

mark.bitterlich(at)navy.m
Guest

Posted: Thu Jun 25, 2015 11:55 am Post subject: Engine roughness, as in stops. starts. stops. starts.

Good Stuff as usual Rob.



Mark

--

jan.mevis(at)informavia.b
Guest

Posted: Thu Jun 25, 2015 12:15 pm Post subject: Engine roughness, as in stops. starts. stops. starts.

Thanks a lot, Rob!

Very valuable information!



Jan



On 25/06/15 18:01, "Rob Rowe" <owner-yak-list-server(at)matronics.com on

behalf of yak-list(at)robrowe.plus.com> wrote:



 	  Quote: 	
		  



IÃ¢Â€Â™m a little late to this discussion about magneto erratic failure when

hot, but hereÃ¢Â€Â™s my 5 pence input for what itÃ¢Â€Â™s worth.



A few years back I assisted in the commissioning of a magneto tester and

in so doing ended up researching the nearly 100 year old information on

this topic and discovered just how nuanced it is. Essentially this

technology reached its peak interest post (Great) war, with research

paper references going back to the 1860s!



For someone who reads a lot of technology papers itÃ¢Â€Â™s a humble reminder

that latter day technical research is not the only source of learning or

innovation.



IÃ¢Â€Â™ve provided links to the research papers below, but first IÃ¢Â€Â™ll

summarise some thoughts that MAY be a scenario for our YAK mag failure

experiences;



1 Ã¢Â€Â“ To create a reliable spark (at least across an air gap on a magneto

tester) a Ã¢Â€Â˜teaserÃ¢Â€Â™ electrode is needed to create an ion rich area to

help allow the spark to form. If this is not present then a spark may

form irregularly depending on ion availability.

Point #1 - an ion rich environment is conducive to flash-over



2 Ã¢Â€Â“ With increasing height air density reduces, as does its electrical

insulation properties.

Point #2 Ã¢Â€Â“ as height increases the voltage required for a flash-over

inside the magneto reduces



3 Ã¢Â€Â“ A leaner cylinder mixture increases the voltage required for a

spark-plug to fire

Point #3 Ã¢Â€Â“ leaning the aircraft in cruise increases the magneto voltage

required for spark-plug operation



4 Ã¢Â€Â“ Magneto impedance (as weÃ¢Â€Â™re referring to its AC properties) is

related more to inductance than resistance with rising frequency

(increasing engine RPM).

Point #4 Ã¢Â€Â“ in the cruise with reduced RPM then magneto resistive

heating may be more apparent, aggravated by #3 where the cruise also

requires a higher magneto energy level to be generated



>From the above we might infer that when in the cruise at height the

>magnetos are at their mostly likely to heat up and are more vulnerable

>to air insulation break-down.



Now put this in conjunction with Jan MevisÃ¢Â€Â™s observation, that the

variable construction quality of the winding insulation (with heat) can

lead to any trapped moisture vaporising and breaking down the insulation

across weak points.



Then such a break-down would create an ion rich environment around the

windings that could trigger premature & successive flash overs to other

weak points impacting engine operation - in much the same way as

lightning storm ions from an initial strike may often lead to the

triggering of multiple events. In this case each event progressively

weakens the secondary insulation, making it more likely to fail

subsequently when subjected to similar conditions.



Now this is all subject to a LOT of contributory variables, hence why

such a perfect (ion) storm failure mode might be a highly unpredictable

initial occurrence & subject to small environmental changes that might

push a marginally functioning magneto finally over the edge.



Anyway so much for my conjecture, here are the research paper links Ã¢Â€Â¦

enjoy!



Characteristics of  High Tension Magnetos (1920) Ã¢Â€Â“ NACA #58

http://naca.central.cranfield.ac.uk/reports/1920/naca-report-58.pdf



Simplified Theory of the Magneto (1923) Ã¢Â€Â“ NACA #123

http://naca.central.cranfield.ac.uk/reports/1923/naca-report-123.pdf



The Sparking Voltage of Spark Plugs (1925) Ã¢Â€Â“ NACA #202

http://naca.central.cranfield.ac.uk/reports/1925/naca-report-202.pdf

Brgds, Rob





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=444037#444037

JL2A

Joined: 07 Apr 2015
Posts: 113
Location: Australia

Posted: Mon Jun 29, 2015 4:32 am Post subject: Re: Engine roughness, as in stops. starts. stops. starts.

 	  Quote: 	
		  If you tune for "perfect combustion" on these engines, the CHT will head to the moon. So when you introduce a spark like an MSD produces... it is not just a spark, it is an extremely long duration event, which turns more of that fuel into energy, and the result is more power produced, but also less cooling, since more of that excess fuel is now turned into power. If you tune for "perfect combustion" on these engines, the CHT will head to the moon. So when you introduce a spark like an MSD produces... it is not just a spark, it is an extremely long duration event, which turns more of that fuel into energy, and the result is more power produced, but also less cooling, since more of that excess fuel is now turned into power. 	




Thanks Mark, very interesting. I had not considered a very rich mixture and the effects spark on flame propagation. Your example of smooth cold idling is interesting and am assuming it illustrates the benefits of spark on very rich mixtures.



In those comments I had assumed we were talking about 'normal' engine operation, i.e., cruise or 50-70% power. I had no idea that the M14R 450 PS engine runs extremely rich even at this setting.  	  Quote: 	
		  Fuel consumption is about twice the consumption of a standard engine. 	
 



Any idea why? 



My non-expert knowledge can only guess that pulling 450PS out of this engine even at cruise power the internal cylinder pressures are still so high (in relation to the initial design of 360hp) that the only way to slow combustion down enough (hence lower ICPs) is to run very rich mixture.



Which leads to another point - and if I'm wrong above then I'm justing getting even more wrong but hey, I'm learning stuff here - why not run these engines very lean of peak. A much more cost effective way of lowering ICP's and as practised on very high specific output western radial engines like the R-3350 etc. It sounds as though the MSD would be of great benefit to smooth and efficient LOP operation!

jan.mevis(at)informavia.b
Guest

Posted: Mon Jun 29, 2015 8:13 am Post subject: Engine roughness, as in stops. starts. stops. starts.

The 450 PS engines run very rich by design. At full power, the CHT and oil

temp go to the red zone very fast.

I replaced the standard oil cooler by an oil cooler from an MI 8

helicopter (a lot bigger).

Now oil temp is ok, all the time.

But CHT can be problematic. When it's very hot outside, I simply don't fly.

Another peculiar thing about the 450 PS engine: CHT has to be kept above

170 degrees centigrades (when in the circuit).

At lower temperature the plugs foul up rapidly.

Fuel consumption of the M14R is about 130 liters/hour at 82/80 settings.

At fully fine, full throttle, it is 220 liters/hour.

The blower in the supercharger runs tremendously fast and has been

constructed by Lyulka (now Saturn) the company that makes the engines for

the Flanker etc.

Intake pressure goes to 1150 mmHg.

So, for a 25% increase in power, I have to feed the horses twice as much.

But the reward is absolutely amazing. You get an incredible torque.

Jan

On 29/06/15 14:32, "JL2A" <owner-yak-list-server(at)matronics.com on behalf

of info(at)flyingwarbirds.com.au> wrote:

 	  Quote: 	

> If you tune for "perfect combustion" on these engines, the CHT will

>head to the moon. So when you introduce a spark like an MSD produces...

>it is not just a spark, it is an extremely long duration event, which

>turns more of that fuel into energy, and the result is more power

>produced, but also less cooling, since more of that excess fuel is now

>turned into power. If you tune for "perfect combustion" on these

>engines, the CHT will head to the moon. So when you introduce a spark

>like an MSD produces... it is not just a spark, it is an extremely long

>duration event, which turns more of that fuel into energy, and the

>result is more power produced, but also less cooling, since more of that

>excess fuel is now turned into power.

Thanks Mark, very interesting. I had not considered a very rich mixture

and the effects spark on flame propagation. Your example of smooth cold

idling is interesting and am assuming it illustrates the benefits of

spark on very rich mixtures.

In those comments I had assumed we were talking about 'normal' engine

operation, i.e., cruise or 50-70% power. I had no idea that the M14R 450

PS engine runs extremely rich even at this setting.

> Fuel consumption is about twice the consumption of a standard engine.

Any idea why? 

My non-expert knowledge can only guess that pulling 450PS out of this

engine even at cruise power the internal cylinder pressures are still so

high (in relation to the initial design of 360hp) that the only way to

slow combustion down enough (hence lower ICPs) is to run very rich

mixture.

Which leads to another point - and if I'm wrong above then I'm justing

getting even more wrong but hey, I'm learning stuff here - why not run

these engines very lean of peak. A much more cost effective way of

lowering ICP's and as practised on very high specific output western

radial engines like the R-3350 etc. It sounds as though the MSD would be

of great benefit to smooth and efficient LOP operation!

Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=444157#444157

mark.bitterlich(at)navy.m
Guest

Posted: Mon Jun 29, 2015 8:23 am Post subject: Engine roughness, as in stops. starts. stops. starts.

 	  Quote: 	
		   Your example of smooth cold idling is interesting and am assuming it illustrates the benefits of spark on very rich mixtures.


	


The MSD system actually stands for "Multiple Spark Discharge".   At idle, there are actually multiple "sparks" occurring at the plug that go a long way to initiate a solid burn.  The same premise could be shown on an old 327 Chevy engine with a Rochester carb and a temperature controlled choke plate.  In cold weather on initial start-up, that engine had to be idled quite high and with a very rich mixture.  Look at what we have today with direct port fuel injection, computer controlled ignition, etc.   You turn the key, the engine starts and runs like a watch.  The only cold start mechanism we have on the M-14 is prime, and the rest is left up to the operator.  Get it started, and keep it running, often with continued shots of prime.  The MSD system was an amazing demonstration of what good ignition can do.  The video in question actually compared running on one M9F mag, and then bringing in the MSD.  It was not a small change, it was like a "wow, listen to that" moment.  



 	  Quote: 	
		   In those comments I had assumed we were talking about 'normal' engine operation, i.e., cruise or 50-70% power. I had no idea that the M14R 450 PS engine runs extremely rich even at this setting. 


	


Actually "normal" engine operation of the M-14 runs the gamut.  You mention cruise at 50-70% power.  Some owners of these engines do run them like that, including many on this list.  However, many others on this list, including myself by the way, do not.  My engine RARELY spins below 80%, except when I taxi.      There are reasons for this, but it is in the end an individual choice.  An example is many of the guys running these engines in competitive aerobatics.  They are either WFO, or at idle.  Very little in-between, and this does not seem to bother them at all.  In fact, I believe the M-14 likes to be run hard as long as CHT and oil temps are within range.  Of course this is completely open for debate as many feel otherwise.  The only real key takeaway from this is the fact that engine cooling on the M-14 is impacted tremendously by adding extra fuel.  The last thing to remember is that THERE IS NO MANUAL MIXTURE CONTROL.  Mixture is adjusted automatically by a barostat internal to the pressure carb.  This is not unique to the Russian engines alone.  Lycoming did the exact same thing with the GSO-480 series, running a PS-7BD pressure carb, and in fact with those engines if you pulled back on manifold pressure while keeping engine RPM up, the CHT and EGT's would climb to the moon once again because the when you pulled back on the throttle, the auto-mixture control would make the engine go lean and up go the temps.  You actually have to keep manifold pressure UP, to get the engine rich, to cool it.  Same exact thing the Russians did.  



 	  Quote: 	
		  > Fuel consumption is about twice the consumption of a standard engine.


	


 	  Quote: 	
		   Any idea why?


	


The more power generated, the more heat has to be dissipated.  



 	  Quote: 	
		   Which leads to another point - and if I'm wrong above then I'm justing getting even more wrong but hey, I'm learning stuff here - why not run these engines very lean of peak


	


Because there is no manual mixture control.



Mark



--

richard.goode(at)russiana
Guest

Posted: Mon Jun 29, 2015 9:00 am Post subject: Engine roughness, as in stops. starts. stops. starts.

We funded OKBM (Vedenyeev) for the development of the M 14 R. It genuinely

does give the power, but is rather too specialised an engine for general use

as Jan implies. As he correctly says, Lyulka were responsible for the

supercharger, which is where the extra power is developed.



If you look at the impeller and diffuser of a standard engine, you will see

that, in supercharger terms, they are very crude with the vanes only having

single-plane curvature and clearly much less efficient than they could be.

So Vedenyeev went to Lyulka, who make the exceedingly fine and powerful jet

engines for the Sukhoi 27 family of fighters, and they produced a new

impeller and diffuser with compound curvature.



Also the impeller is turned a little faster - unfortunately I can't find the

figure at the moment - than the M 14 PF, which again helps.



Richard Goode Aerobatics

Rhodds Farm

Lyonshall

Hereford

HR5 3LW



Tel:  +44 (0) 1544 340120

Fax: +44 (0) 1544 340129

www.russianaeros.com

--

JL2A

Joined: 07 Apr 2015
Posts: 113
Location: Australia

Posted: Tue Jun 30, 2015 5:07 am Post subject: Re: Engine roughness, as in stops. starts. stops. starts.

Interesting stuff!



good to compare it to the R-985, which seems a more efficient way of producing 450hp. But would look a bit funny hanging on the front of a Yak

jan.mevis(at)informavia.b
Guest

Posted: Tue Jun 30, 2015 5:40 am Post subject: Engine roughness, as in stops. starts. stops. starts.

The R-985 is about 70 kg heavier than the M14x so it would be a serious

balance problem bolting this on a Yak.

The R-985 also has a much larger displacement I think.

So, the Russian design is rather good: more power for less engine weight

(but I am biased, I admit it).



Jan





On 30/06/15 15:07, "JL2A" <owner-yak-list-server(at)matronics.com on behalf

of info(at)flyingwarbirds.com.au> wrote:



 	  Quote: 	
		  



Interesting stuff!



good to compare it to the R-985, which frankly seems a way more efficient

way of producing 450hp. But would look a bit funny hanging on the front

of a Yak





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=444222#444222

Display posts from previous:

	Matronics Email Lists Forum Index -> Yak-List	All times are GMT - 8 Hours Goto page 1, 2 Next
Page 1 of 2

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum