Double Peak When Locating ROP O-360C1A

[paulsmeds]

Question for engine guru's. O-360C1A w/CS prop. Engine starts easy, runs smoothly, seems to have plenty of power, but does seem to have a slightly higher FF than others discuss here (@6500 feet, 2400 RPM, 22 MP, 100 ROP about 10 to 10.5 GPH). I also get a deep pop periodically when slowing down in the pattern with MP less than 13". Above 13" smooth. Other than that no complaints!

Locating ROP with the EDM-350 there is a strange behavior of the #3 EGT where it seems to peak twice. It starts the second EGT climb to peak right when the others peak. It is fairly consistent and behaves like this for almost all the ROP locating with the EDM-350. Once I did it super slowly and it resulted in the second graph below where #3, #4 and #1 all have a slight double peak but this is the only time I've seen the others do this.

This looks odd compared to the all 4 EGT smooth peaks I'm used to with fuel injection. Can this point to some condition that needs attention or is this just normal for a carbureted O-360?

 

[paulsmeds]

I think I just solved this. They are not double peaking -- #3 is peaking and at that point LOP but I keep leaning. Then when #2 finally peaks and I start enrichen, then #3 does peak again as it comes out of LOP. The brain light bulb came on right after I posted. I think my only issue is the EDM-350 is not recognizing the #3 peak first even though it is in ROP mode. I'll see if JPI can shed some light on why it isn't detecting the first cylinder to peak.

 

[BillL]

This bugged me on my IO360M1B, and concluded that the first peak both plugs are firing and the real peak you want. The second one is when a plug is misfiring and effectively retarding the timing so the EGT goes back up. I would guess that due to a number of factors, that every cylinder may not exhibit this characteristic.

Try this on and see how it fits your engine.