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Pull till it pops?

cgoldy

Registered User
Moogerah Queensland Australia
This is not a question about LOP vs ROP. But a lot of people talk about the pull till it pops then richen till it disapears method. But what is regarded as a pop? There seems to be 3 stages.

1- slight reduction in rpm
2- slightly perceivable modulation of rpm detected
3- distinct misfire

So what is your "POP"?
 
Another way to get extended range. Select operation on one mag. reduce mixture until a slight ruffness, now select both mags engine will smooth out. Ole time trick to extend range. Try at your own risk.
 
A more careful way of leaning involves setting a constant cruise speed, then leaning in small steps. Note your cruise speed, which should be increasing as you progressively lean. When you lean more and the speed decreases, you have gone over. Back off a half turn or so and there's your mixture setting. The whole process may take 5 minutes.
 
It varies with each engine. If all the cylinders are getting a nice even mixture of fuel you will only get a reduction of RPM but the engine will continue to run fairly smooth and there will be a broad band between leaning it out and actual roughness/stopping. On these engines it can be hard to tell where the first point of "too Lean" is so use the first hint of RPM decay. Other engines will go from smooth to rough very quickly as you lean them out. There will be no doubt where the first point of roughness (or popping ) is. Push the throttle in until it smooths out and you are there.

Bill
 
Here's the recommendation from Lycoming's Tips booklet: NOTE — When leaned, engine roughness is caused by misfiring due to a lean fuel/air mixture which will not support combustion. Roughness is eliminated by enriching slightly until the engine is smooth.

I have repeatedly, and on several engines compared this procedure with the procedure of leaning using EGT gauges in airplanes with four probe EGT/CHT gauges, and frankly, I found that Lycoming's recommended technique really comes VERY close to the EGT monitoring process.

Note that Lycoming specifically recommends against running their engines (with few exceptions) lean of peak EGT.

MTV
 
another useful tool is a horizon digital tach.. Its easy to see exactly when you get any rpm drop. If your engine goes rough at the same time as it starts dropping RPM you might want to check for induction leaks as this indicates 1 cylinder that is already way leaner than the rest and drops off as soon as you pull the mixture out.

Dave
 
...somewhere between #2 and #3...then push the mixture back in about 3/8ths of an inch.

I, too, have compared this procedure to using the EGT gauges. The simple leaning procedure works every time. IMHO D
 
Thanks all. I think I have it a little clearer now.

Tim - that link answered allot of my concerns of getting too lean.

Thanks again
 
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