Check my leaning technique

pa38112 · #1 02-20-2017, 07:50 AM

I like to run LOP all of the time. Here is what I do when I am stuck down low. Looking for feedback. O-360-A1A, 100LL, FP

Below 3,000 feet I will fly at 2,400rpm and lean to about 20LOP. At this point my RPM's have dropped to about 2,100rpm. Then I go to Wide open throttle, which causes roughness. I then enrich until the engine is reasonably smooth and back at 2,400rpm. I do it this way because I don't want to lean through the peak at WOT down low, but this way I am not 100% sure that I am actually LOP. At a given lean setting, does the A/F ratio stay relatively steady through different throttle settings? My Fuel flow is about 8.4, which is 70% power IF I am LOP. CHT's are all 350 and below.

lr172 · #2 02-20-2017, 07:59 AM

Your engine will require infinitely variable amounts of fuel flow based mostly upon RPM/MAP combination. Think of your mixture knob as a restrictor, with any unique setting allowing a specific maximum fuel flow and allowing any flow below that maximum. Any time you make a change that will require an increased fuel flow, such as going from 2100 -> 2400 RPM, you will need to adjust the mixture to allow additional fuel flow to maintain the same air fuel ratio (i.e. the LOP %age).

When I level off at 3000', I adjust approximate throttle for my desired RPM/speed and then pull the knob back till I hear the engine speed fall off. I then increase the mixture as I adjust up to my desired EGT to get 30-40* LOP. I then tweak the throttle setting to the desired RPM or airspeed then re-adjust the mixture back to my desired EGT, if necessary. If you want, you can then enrich to peak and go lean again to hit an exact LOP setting. I have FI / EI and can go well over 100 LOP. With a carb and mags, you want to be carefull not to overdo the pull as it will get real rough if you go to far and upset your passengers.

Larry

BobTurner · #3 02-20-2017, 01:11 PM

It sounds like you do not have a 4 cylinder egt readout. If this is true, there is no way to really know what's going on in each cylinder. Some carb'd engines have good fuel-air distribution; some do not.