PPonk engine not getting enough air?

Katamarino

Katamarino

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Katamarino
I'm getting some weird behaviour from my 182, which I bought with a PPonk engine with 80 hours on it. At lower altitudes and cooler temps, it is pretty great; my EGTs and CHTs are fairly close and manageable. However, above about 5,000ft, the CHTs and EGTs on cylinders 4, 5, and 6 go south fairly rapidly and the engine starts to vibrate, the higher I go the worse it gets. See the associated engine trace from a good exemplar flight:

https://savvyanalysis.com/flight/2573918/71d6625b-d517-4a08-8269-a9c71913abf8

And some shots from the JPI:

Low down, higher power:
KlUblUCl.jpg


Low down, lower power:
ocjT1jQl.jpg


High up (only 10k feet, though), engine getting crappy:
N3RSBtgl.jpg


All I can think of so far is that cylinders 4,5,6 aren't getting enough air, so once climbing to thinner air they start to get way too rich.
 
Insulate your balance tube. In cool temps fuel condenses and the front cylinders run rich. Look at resident 470s and 520s in Alaska and you'll find their balance tubes insulated.

16.6 gph at 53% hp is a lot of fuel. I'm under the flow rate at 24.5"/2450 at 1000'.
 
My HP% isn't calibrated yet; but, thank you, I'll look into doing the balance tube!
 
That was taken while I was playing with mixture to try and figure things out. Can you open the Savvy link? Gives full data for that flight.
 
I'm looking at the screen you used in your example. At those power settings and altitude you were supplying too much fuel. Temps bear that out. As far as engine roughness? Too little air is relative to too much fuel. I'd still say the balance tube is suspect.
 
Mixture is way too rich for 10K, should be more 11 gph. I assume you have carb temp somewhere on the panel (if not, get that asap). Try partial carb heat to keep carb temps in the low 40s (F), that tends to help balance out the fuel distribution in our Pponk.
 
PPonk called me and talked me through a whole bunch of ideas and tips. Amazing service from those guys!!
 
Ross, run carb heat and lean it out, all EGTs get even, I also run high GPH or else the EGTs get too high along with CHTs, about 13 to 14GPH at those altitudes
 
Check for induction leaks. Happens a lot with these.
 
Pponk has an approval to convert an O-470 to 520 ci. You can also start with an IO-520. PPonk, Kenmore, and TX Skyways all have a version of that path.
 
I have heard this word few times before and was thinking this would be some kind of texting lingo. Interesting.
Thanks
 
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Don’t have any experience with a pponk but the stock O-470Us and R’s do this when carb temps are in the freezing range. Lean it harder and run with partial carb heat. There is a chapter in the “Skylane Companion” book about this.
 
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