My IO360 leaning graph

I haven't seen a graph that appears the same as this one from my engine so I'm curious what others have to say about this.

The top chart is showing Fuel Flow along with the EGT's and the bottom has percent power with CHT.

I was running 21" at 2350RPM approx. 63 percent power on the dynon screen when I started leaning. FF on #4 peak EGT was about 7.8 and buy the time #1 reached peak, FF was 7.2


About the time cylinder number 1 hit 20LOP the engine started popping out the exhaust and I assume that's the reason for the climb in EGT's.
I kept leaning until the engine almost died then went back to full rich and got back to the airport so I could download the info.

This is a fairly new engine from Lycoming with one mag and a Pmag both timed to about 23BTDC.

I would guess that afterfies would raise EGT, but have never observed it. Its more likely that when you got very lean, the mag's spark wasn't strong enough to light the lean mixture and that would cause retarded timing and the spike in EGT on the two leanest cyl's. The Pmag has a stonger spark and therefore can light a leaner mixture than the mag.

You can tighten up the spread in peak EGTs with custoem restrictors from AFP. Very inexpensive and will yield slightly more efficient cruise power with an ability to get leaner without roughness.

Larry

Too many variables, so perhaps time to rebase.

You know #1 cylinder is getting too much gas so start there. Replace the #1 injector nozzle with 0.027" and keep all the rest at the stock 0.028". Nozzles in different sizes are available from Airflow Performance for ~$26. They are identical to the stock nozzles you got with the engine, just a different size.

Recommend you retime both the mag and pMag for 25 degrees BTDC (the standard timing for a parallel valve IO-360). Remember when timing the pMag to get that 25 degrees you set the pMag timing with the crank at TDC.

Keep the pMag jumper in.

Do another data run and see what you have. You may need to change another nozzle before you are done. This is an iterative process, but usually 3-5 data runs with get you in the ballpark.

Carl

Your GAMI Spread is about 0.6 GPH, and at such a low power 10dF LOP is all you need.

As suggested above get that tweaked and aim for a 4 cylinder engine of a spread of 0.3 GPH or better. Then life will be good.

I retimed the engine to 25 degrees and replaced the stock .028 injectors in #1 & 2 to .0275

Getting closer but #1 is still rich so I'll be installing a .027 size injector and trying again.

Before


After