LOP Help

[macrafic]

OK, I am not interested in restarting the LOP/ROP debate. I have read significant amounts of material, listed to many experts, read the VAF forums, etc. I have made the decision to run LOP on my IO-360 fuel-injected std bore engine.

My question is for those of you running LOP, especially those with a G3X with Lean Assist (I have the non-touch G3X, if it makes a difference). How do you use that feature? I have read the Garmin documentation and am just not getting it.

Also, how much LOP is everybody running?

[rleffler]

I would test to see what your fuel flow is (i.e. GAMI test) before I would worry about how far to lean. You want your fuel flow to be close in each injector when you get peak EGT. If one cylinder peaks ahead or behind the rest, your engine won't run as smooth until they're balance.

For example, my engine came from the factory with a 1.2 spread. After balancing the injectors, I was able to get it down to .2

Here are the instructions on how you can measure things yourself.

http://airflowperformance.com/wp-con...structions.pdf

Don at Airflow Performance can provide the injectors. Just let him know who's FI system you have.

[Auburntsts]

Essentially if you use the G3X's lean assist function and copy the fuel flows as each cylinder peaks in addition of the other data, you are performing the alternative method outlined in AFP's version of the GAMI test that Bob provided the link to.

As to your question as to how the lean assist works, after enabling the assist, just lean until the EGT column on the display goes "blue" for a given cylinder. Once it does indicating that a cylinder has peaked the actual peak EGT number will be displayed in gray at the top of the column for each cylinder that has peaked. The number at the bottom of the column is the "delta" or the amount of decrease from peak as the EGT temp drops as you continue to lean the mixture. That "delta" number will be in a solid blue box for the first cylinder to peak, and outlined with a thin blue border for the last cylinder to peak. These numbers really aren't that important. What's important is the fuel flow as each cylinder peaks and the flow spread from when the first cylinder peaks to when the last cylinder peaks. The reason being if the spread is too great from first to last to peak, the first and possibly other cylinders, will end up way too lean by the time last gets LOP resulting in roughness and loss of power.

Note: After doing the GAMI test and looking at the data, in practice I simply lean to specific fuel flow.

[N941WR]

Going LOP has a lot to do with your ignition, not just your fueling.

I have a carbureted O-360 and can run fairly well balanced up to 100 degrees LOP and that is because I have dual electronic ignition.

The temperature LOP has a lot to do with how far way from the exhaust port the temperature probes are placed.

Thus it is difficult to compare your numbers to mine, or anyone else.

[MarkW]

Hey Rich,
Todd has answered the question of what the display looks like on the G3X.
I pick an altitude and cruise then start the process. ( I have been leaning all along just not using the lean feature until I get everything settled in). Full throttle and what I feel is close to peak, I hit the lean button and then start slowly leaning. Slow is the key. After a while you get to remember about where peak is so that you can get to peak quicker. I lean until I see all four cyl. LOP and then go another 50-100 degrees. I can usually get about 100 LOP before I starts to loose significant power/speed. Once I get a little too far, say 150 LOP it gets too slow. I only loose about 7 knots from ROP to LOP operation and the GPH drops 3-5 GPH. Nice and smooth and things start to cool further down.