Can't get LOP.

AAflyer · #1 10-30-2016, 05:54 PM

I've got about 35 hours on my new AeroSport IO-360 with dual PMags. It's running pretty darn well..until I start trying to lean it below 'peak'.
Almost as soon has I get the last cylinder to peak...which is only about 40 degrees behind the others...the engine loses significant power. It doesn't really run 'rough'..it just bogs down A LOT.
I'm not quite ready to practice my in-flight engine re-start procedures, so I always chicken out and advance the mixture.
If this helps...I really don't get much of an RPM rise when I kill the engine by pulling the mixture to ICO.
Any thoughts?
P-Mag "curve"?
Mixture setting at fuel servo?

Thanks in advance.

BobTurner · #2 10-30-2016, 05:58 PM

Sounds like you need to balance your injectors, so all cylinders peak at the same time.

Rupester · #3 10-30-2016, 05:59 PM

When I go from ROP to LOP I always lose some RPM. In most cases its around 100 RPM, once in awhile a tiny bit more.
In the idle condition, when fully leaned RPMs should rise around 40. If it is more than that, your idle mixture is likely too rich.

SmilingJack · #4 10-30-2016, 06:00 PM

Ohm out your wires per the Pmag manual.

Carl Froehlich · #5 10-30-2016, 06:12 PM

180hp or 200?

What is total fuel flow when the first cylinder peaks? Total fuel flow when the last cylinder peaks?

Are you running with the pMag jumpers in or out?

Carl

dtw_rv6 · #6 10-30-2016, 06:17 PM

The lack of engine RPM rise is unrelated to your inability to run LOP, but you should adjust the mixture control on your fuel servo. What you describe indicates that it is set too lean for your current weather conditions. I usually change mine twice a year - once in the fall for colder more dense air (richer setting), and once in the spring for warmer less dense mixtures (leaner fuel setting).

Don

Toobuilder · #7 10-30-2016, 06:19 PM

Quote:

Originally Posted by AAflyer

...I'm not quite ready to practice my in-flight engine re-start procedures, so I always chicken out and advance the mixture...

Just so you know, advancing the mixture IS the "restart procedure" in this scenario.

As for the other thing, there is a loss of power when going LOP - how much depends how far you go, and THAT depends on the FF spread between the first and last cylinders to peak.

scsmith · #8 10-30-2016, 07:25 PM

40 degrees seems like a lot. If I understand what you meant, that when the last cylinder peaks, the first one or more are already 40 degrees lean of their peaks. Thats kind of a marginal spread for useful LOP. That one that leans last, (its richest) you could try putting a slightly smaller injector in that cylinder. If you have 0.028" injectors (the most common) then try an 0.0275" or 0.0270". They are $27 each from Don at Air Flow Performance. buy a couple of each. Only change one cylinder at a time, and repeat your leaning test.

I should say though, that before you do much else, you really should do the classic GAMI test and write down what you have, so you can really see that the other cylinders are much leaner, and where they stand relative to each other.

It is normal to get some power loss as you go lean. If you are making really small changes (0.1 gph at a time) you will hardly notice. If you do it all at once, then yeah, you will hear the engine power drop off.

RV8iator · #9 10-30-2016, 08:55 PM

Balance your injectors and your problem will go away.

lr172 · #10 10-30-2016, 10:49 PM

Balancing the injectors is a good idea, but it really is an efficiency thing, not a performance thing. Right now, that last cylinder is running at peak, not 40 LOP like the others. Once you balance it, it will produce less power like the others and total power output will drop a small tad as will the FF. If your cylinders don't peak at the same time, you are throwing extra fuel at the rich ones without any real benefit. This situation also leaves the rich cylinder with a higher ICP. That cylinder is not getting the detonation margin benefits of running LOP. It's ICP will be higher, putting more stress on the cylinder and decreasing detonation margin.

40* LOP will produce a good bit less power than peak or best power. You need to qualify "really bogs down" and "a LOT."

Measure your RPM and TAS at Peak or best power (wherever you have it that is is not bogged down) and then again at 40* LOP and post here. The group will tell you whether or not that is consistent with the norm.

Larry