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Richard Pike
Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee
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 Posted: Mon Apr 19, 2021 10:21 am Post subject: Jetting puzzler |
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Finally got the 3.47:1 E gearbox, the 72" three blade Warp Drive prop and the 582 to be happy with each other. And working around our trashy thrashy spring winds, it only took six weeks...
The problem was that every time I throttled back to cruise, the 582 "fell off the pipe." Ran great on takeoff and climbout, made no difference if I pitched the prop for a 6,000 rpm climb, a 6,250 rpm climb, or a 6,450 rpm climb, when I pulled the throttle back to anything less than 5,000, the engine would sag off to around 4,600 and misfire, and the egt's would go from around 1100 - 1150 to around 1000. A bit low, but not horrible.
Jetting was exactly as specified, new plugs, new plug caps, cleaned and reoiled the air filter, new choke valves, as close to the book as I could get it, no joy.
Yesterday I pulled the #55 idler jets and replaced them with a set of #50's I had. Bingo! Not great, but way better. Then I dropped the jet needles one notch and I've got my airplane back. Ran perfect.
This morning I added some pitch to the prop and tried it again, still perfect.
So here's the question: why would going from a 2.58:1 B box and a two blade 68" Ivo to a 3.47:1 E box and a three blade 72" Warp require leaner jetting? There is probably a good reason, and one of you probably knows what it is.
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_________________
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0
Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing. |
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Jerry-TS-MkII
Joined: 23 Aug 2017
Posts: 79
Location: Indiana
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| Posted: Mon Apr 19, 2021 1:18 pm Post subject: Jetting puzzler |
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Richard..
Granted this is a educated guess.. and even the "educated" part could be
in question. But knowing how 2 strokes run.. and how you have made your
changes in gear box and prop? As a computer tech, we used to align floppy
drives, and a part of that was observing the "instantaneous" speed of the
disk. How does that relate? You have a difference in the gear box type,
the gear ratio, the prop inertia )due to diameter change), and likely it's
actual mass too. And being a 2 stroke, most of the function of the engine
depends on the flow thru the engine, and even the "super-charging effects"
of a tuned pipe. If you had measured the exact speed of each part of the
rotation, and how that affects fuel flow, loading, flame progression, and
general timing.. all of the new toys may have simply changed how the engine
responds.. and while I don't know the exact amount of difference in fuel
flow from a idle jet change, or one click of the needle going leaner.. but
clearly those carbs are designed as super versatile, in their range of
available adjustments. I wouldn't question the slight changes making what
appears as big differences. Just pat yourself on the back for tweaking it
correctly! Sounds like you have it dialed in, perfectly!! And there are
other folks (reminded of the HKS and all those mods) that never got that
plane to fly right!
As other have said here, worth everything you didn't pay for the possible
reasons above. Best Wishes! Enjoy! Jerry
On Mon, 19 Apr 2021 11:21:23 -0700, "Richard Pike"
<thegreybaron(at)charter.net> wrote:
| Quote: |
<thegreybaron(at)charter.net>
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| Quote: |
Finally got the 3.47:1 E gearbox, the 72" three blade Warp Drive prop
and
|
| Quote: | the 582 to be happy with each other. And working around our trashy
thrashy
|
| Quote: | spring winds, it only took six weeks...
The problem was that every time I throttled back to cruise, the 582
"fell
|
| Quote: | off the pipe." Ran great on takeoff and climbout, made no difference if
I
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| Quote: | pitched the prop for a 6,000 rpm climb, a 6,250 rpm climb, or a 6,450
rpm
|
| Quote: | climb, when I pulled the throttle back to anything less than 5,000, the
engine would sag off to around 4,600 and misfire, and the egt's would go
from around 1100 - 1150 to around 1000. A bit low, but not horrible.
Jetting was exactly as specified, new plugs, new plug caps, cleaned and
reoiled the air filter, new choke valves, as close to the book as I
could
|
| Quote: | get it, no joy.
Yesterday I pulled the #55 idler jets and replaced them with a set of
#50's I had. Bingo! Not great, but way better. Then I dropped the jet
needles one notch and I've got my airplane back. Ran perfect.
This morning I added some pitch to the prop and tried it again, still
perfect.
So here's the question: why would going from a 2.58:1 B box and a two
blade 68" Ivo to a 3.47:1 E box and a three blade 72" Warp require
leaner
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| Quote: | jetting? There is probably a good reason, and one of you probably knows
what it is.
--------
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0
Forgiving is tough, being forgiven is wonderful, and God's grace really
is
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jhauck
Joined: 02 Jan 2020
Posts: 26
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| Posted: Mon Apr 19, 2021 2:42 pm Post subject: Jetting puzzler |
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New system is not loaded as much as your old system at mid and low range. Two strokes are very sensitive to loading and unloading, mixture, and EGT. I did lot of experimenting way back in my two stroke days. Never had a problem I couldn't solve. Then my first flight to Alaska with the new 80 hp 912 and I developed mixture problem I couldn't solve until well after I got back home in Alabama. And I discovered the solution to that one by accident and experimenting with the enricher in midrange. That was 1994.
You are working with a system that is far from standard, especially on a Kolb.
John Hauck
On the Great Loop in Astor, Florida
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slingshot003
Joined: 10 Mar 2017
Posts: 28
Location: FL USA
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| Posted: Tue Apr 20, 2021 7:23 am Post subject: Re: Jetting puzzler |
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Richard,
That is a puzzler. Raising gear ration unloads the engine which would require leaning the carbs, but you pitched the prop accordingly so the load should have returned to normal. This was the case for full throttle so why was it not the case for cruise? My guess is that the Warp Drive prop has similar characteristics at full throttle as your previous prop, but it also has different characteristics at cruise compared to the previous prop. Since Warp is turning slower and since it is probably stiffer, it probably had much less induced twist at cruise compared to the previous prop so it does not bite as much air, thus less loaded, thus leaner carb at cruise. You loaded (pitched) the Warp to match the load of the engine at full power so that would guarantee that the jetting would be the same because the previous setup was also matched for full power. It would then seem that the Warp behaves differently at midrange & turning slower than the other setup, thus demanding a leaner midrange jetting. This would be my theory. -Richard Swiderski
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slingshot003
Joined: 10 Mar 2017
Posts: 28
Location: FL USA
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| Posted: Tue Apr 20, 2021 7:46 am Post subject: Re: Jetting puzzler |
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Richard,
Since you had a significant decrease in demand for fuel at cruise rpm, it would be interesting for us to know if at that same rpm did your cruise speed remain the same or even increase? If so, then we would know how to increase the range of our Kolbs, as less fuel for the same or more speed would mean a more efficient setup. Maybe you could take note and let us know?
Also, do you have the data regarding the change of thrust at full power compared to your initial setup? Theoretically we know it should be more, but is it significantly more? Can you tell "by the seat of your pants" at take-off?
Thanks, -Richard Swiderski
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Jerry-TS-MkII
Joined: 23 Aug 2017
Posts: 79
Location: Indiana
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| Posted: Tue Apr 20, 2021 9:26 am Post subject: Jetting puzzler |
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The reason we have PRUs is not to just add weight and complexity. It's to
turn a larger prop at a speed that keeps the tips from going super-sonic or
even close. And as for props? Well you don't see any wind-mill farms with
6' propellers! The larger prop is more efficient, right at the get go.
And yet that makes for larger gyroscopic loads and heavier bearings, and in
many cases, a longer landing gear for ground clearance.
On Tue, 20 Apr 2021 08:46:58 -0700, "slingshot003" <i2bxtn(at)gmail.com>
wrote:
| Quote: |
Richard,
Since you had a significant decrease in demand for fuel at cruise rpm,
it
|
| Quote: | would be interesting for us to know if at that same rpm did your cruise
speed remain the same or even increase? If so, then we would know how to
increase the range of our Kolbs, as less fuel for the same or more speed
would mean a more efficient setup. Maybe you could take note and let us
know?
Also, do you have the data regarding the change of thrust at full power
compared to your initial setup? Theoretically we know it should be more,
but is it significantly more? Can you tell "by the seat of your pants"
at
|
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neilsenrm(at)gmail.com
Guest
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| Posted: Tue Apr 20, 2021 11:52 am Post subject: Jetting puzzler |
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There is a whole lot of science that I don't understand but I learned a bit with my VW. You get a bunch more thrust moving a bunch of air slowly than less air quickly but it isn't that simple. When you have a small prop accelerating a small amount of air a lot you have a wide range of effective speeds that the prop provides thrust. If you have a bigger prop the speed range is less. I think a prop is most efficient when the prop is close to the real pitch of the prop, like a screw going into a piece of wood. I assume when you pull power to cruise you unload the prop because your are getting close to the real pitch of the prop. You should be happy with your big slow turning prop but there is a trade off. Do you pitch the prop for best cruise at cruise RPM or best climb at full power at best power RPM. The most common is to set the pitch for best power in climb, but you may find that your cruise is slower than you want. I set my pitch for best cruise speed at the recommended cruise RPM and live with lower climb power/RPM. I spend most of my time at cruise. I have a abundance of thrust with the big slow turning prop so it isn't a big deal. A few years ago I cut 1/2" off the prop tips to get more climb thrust but I ended up with less cruise and climb thrust.
There has to be people out there that have some real prop knowledge, what do you think.
Rick Neilsen
Redrive VW Powered MKIIIC
On Tue, Apr 20, 2021 at 11:26 AM slingshot003 <i2bxtn(at)gmail.com (i2bxtn(at)gmail.com)> wrote:
| Quote: | --> Kolb-List message posted by: "slingshot003" <i2bxtn(at)gmail.com (i2bxtn(at)gmail.com)>
Richard,
That is a puzzler. Raising gear ration unloads the engine which would require leaning the carbs, but you pitched the prop accordingly so the load should have returned to normal. This was the case for full throttle so why was it not the case for cruise? My guess is that the Warp Drive prop has similar characteristics at full throttle as your previous prop, but it also has different characteristics at cruise compared to the previous prop. Since Warp is turning slower and since it is probably stiffer, it probably had much less induced twist at cruise compared to the previous prop so it does not bite as much air, thus less loaded, thus leaner carb at cruise. You loaded (pitched) the Warp to match the load of the engine at full power so that would guarantee that the jetting would be the same because the previous setup was also matched for full power. It would then seem that the Warp behaves differently at midrange & turning slower than the other setup, thus demanding a lean!
er midrange jetting. This would be my theory. -Richard Swiderski
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Richard Pike
Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee
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| Posted: Tue Apr 20, 2021 6:45 pm Post subject: Re: Jetting puzzler |
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You guys are great; thanks!
I still do not have any good numbers because the wind around here for the last several weeks has been totally uncooperative. Went flying yesterday morning to try out a different prop pitch setting and managed to peg the vario both ways twice within 30 seconds. WHEEEE!!! But not much good for gathering data...
Seat of the pants is amazing, and I am having to relearn a few things. I used to start the takeoff roll stick back while gradually, smoothly feeding in full throttle, stick forward/raise the tail, accelerate some more, lower the tail, fly.
Now - If I start the takeoff roll with stick back and gradually, smoothly feed in full power, it simply lifts off well before it ought to, even as you are getting the stick forward, and it's typically in a right yaw and left roll. Not good and most unnerving.
So I quit that. 2/3 throttle and ease the stick forward until it feels right, then full throttle and lift off, feels perfect. It still gets off the ground in half the distance it used to.
So far it looks like the climb rate is about 25-30% better, and cruise might be about the same as before at similar rpm's, but right now it's hard to say. Can't wait for some decent air to get some real numbers.
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_________________
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0
Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing. |
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Richard Pike
Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee
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| Posted: Fri Apr 23, 2021 4:56 pm Post subject: Re: Jetting puzzler |
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Calm air at sunset, got some good numbers.
Prop pitch is 12 & a half degrees at the tips.
Full throttle rate of climb, 6450 rpm, variometer says 11-1200 fpm.
Cruise speed is 65 mph at 5300 rpm, 70 mph at 5500.
Jet needles in the #2 slot, egt's constant around 1100-1150.
Now that everything is sorted out and working great, it's time to sell the other 582 engine, gearbox, starter, 68" Ivoprop, BRS & the 2 seat trike that goes with it. $2800 takes it all.
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_________________
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0
Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing. |
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