G3X Lean Assist questions

I have been trying to figure out the Lean Assist on my G3X. I can get all the cylinders in the blue but the temps are not even - up to 30 degrees or so different. Im all for leaning the mixture but not really sure what temp I am going for. Questions:

1. How close to the same temp should all the cylinders be?
2. What temp should it be and what is the max - temp?
3. I know from watching Mike and Vic videos that there is a place you dont want to be. What is that place?

I have an O-320 D2A with 160 hp, fixed pitch Catto, and a carb. Use 100ll.

Thanks for the help. I will check out other videos and see what I can figure out.

rockwoodrv9 said:

1. How close to the same temp should all the cylinders be?
2. What temp should it be and what is the max - temp?
3. I know from watching Mike and Vic videos that there is a place you dont want to be. What is that place?

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The actual EGT numbers are not nearly as relevant, the aim is to have them peak as close to each other as possible (even fuel flow within all four cylinder) and within 0.2GPH between the first that peaks and the last is a good goal.
As for what EGT number to shoot for, 50F LOP is the goal but if you can lean even more as long as the engine still running smoothly, that would be great unless you start seeing a great sacrifice in speed. Lastly, the red zone that Mike and Vic refer to is related to the engine power, above 75% power setting or a high CHT, this is when a greater chance for detonation exist.

Thanks. That makes me feel better. I thought the temps were CHT rather that EGT displayed in lean assist. I’m going up this afternoon and will check it out and be sure to keep the power under 75%.

It has been my understanding that there is no red zone below 65% even if ROP. LOP your safe up to 75%. This is from Mike Bush's teaching that the zone is really shaped like a fin. Gives a little bit more detail of where it is safe to run.

You want to learn about the GAMI lean test and be able to run that to understand the "GAMI Spread" on your cylinders before confidently running lean of peak in the "red zone". The GAMI spread needs to be acceptable (around 0.5 GPH) before LOP operation is routinely "doable" (except outside "red zone" where you can't do any harm as noted in Glenn's post). Lots of resources out there on that, may want to start with Martin Pauly's video on the topic:

https://youtu.be/h3bATVXMHQg

Detailed instructions on GAMI Lean Test:

https://www.advancedpilot.com/downloads/GAMI Lean Test.pdf

Some folks hate the Lean Find feature in these engine monitors, because they require you to slowly pull the mixture through the red fin (when above 65% power) in order to find the peak EGT. But I haven't heard any credible claims that you can hurt the engine by doing that when at a power setting of 65% or lower.

I typically climb to 65% or less at WOT (8000 MSL, more or less) and then use Lean Find to get ~50 F lean of peak on the last cylinder to peak, or possibly enrichen a bit to regain some engine smoothness and airspeed if 50F LOP turned out to be too much (usually because I pulled the mixture too quickly and the peak reading wasn't the actual peak).

My technique seems to be sound, and it's definitely simple. I just fly grossly ROP for those short trips where going to 8000 doesn't make sense. I don't care if I burn 10 gph or 12 gph on a flight where the cruise portion is 15 minutes long.

I do have my CHT yellow range marked fairly low, and never see a yellow CHT figure while leaning or cruising. I have had to adjust mixture in the climb to keep CHTs down, but leaning in the climb is another topic altogether.

I run 65% power and LOP at all times in level flight. I used the LOP feature on the G3X enough times to figure out what fuel flows gives me LOP. I always do the big mixture pull even though there is no red zone at 65% power.
If you want to check how far below LOP you are you can lean until the engine stumbles and then enrich the mixture until in smooths out. (the old fashion way that we were taught as a student) You will do no harm and will be certain to be well out of the red zone. You will loose some power and therefore some speed being well lean of peak versus being at peak or just lean of it.

The G3X Lean Assist function works coming up from lean as well. So if you're worried about 'the red fin' you can do a big mixture pull until the engine stumbles, enable lean assist, and then slowly richen the mixture .1 GPH at a time until every cylinder peaks, then lean back down to the desired setting.

Thanks for the info. I have been using the free Savvy reporting but just signed up with the monitored plan and should get a report from my flight data tomorrow or Wednesday. I am really interested what it says.

It may be good enough weather tomorrow and I will try the 65% power, lean until rough, rich a bit, then turn on lean assist and see what I can get it to. Im not sure the -temp I want to achieve but I will see how the RPM's and temp goes.

rockwoodrv9 said:

Thanks for the info. I have been using the free Savvy reporting but just signed up with the monitored plan and should get a report from my flight data tomorrow or Wednesday. I am really interested what it says.

It may be good enough weather tomorrow and I will try the 65% power, lean until rough, rich a bit, then turn on lean assist and see what I can get it to. Im not sure the -temp I want to achieve but I will see how the RPM's and temp goes.

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I would suggest hitting lean assist prior to leaning. It will show when each cylinder hits LOP and then calculates each cylinder temp below peak as you continue leaning. Lean very slowly. You will see how far LOP you can go before the engine starts to run rough. Watch fuel flow as well. This will tell you fuel flow from Peak to maximum LOP.