First off, this is relating to my RV7A, with IO-375 low compression Aerosport engine with dual Pmags. I also run the EI Commander that lets me see and change the timing etc. I do like the setup I have, and I wold not want to have it without the EI Commander.
Recently I called Bill Repucci and he walked me through the steps to retard the timing in an effort to get CHTs more in control as they would go past 400F very easily. We reduced the timing advance by shifting the curve 2.8 degrees and this adjustment did make a difference. Now that I have flown this way awhile, I think maybe even more retardation is something to consider. I will post a savvy analysis plot of my recent light here:
https://www.savvyanalysis.com/flight/1493062/db5110c8-30ea-4bfd-b93f-9cda52ffecd2
Too bad the EI Commander can't be part of the data log posted above. I did not take notes on the flight, but remember seeing 23 degrees advance at full power at 4,500' with 80F OAT. The curve will advance up to about 30 deg. up at altitude with lower MAP. 23 degrees does not seem like much advance but reducing it by the 2.8 degrees did help so maybe even less advance will help more? That is my question.
The 2.8 deg. adjustment made my CHTs more manageable for sure, but I still have to dump fuel through the engine to keep them below 400F in full power conditions down low as the logged data from the flight shows.
Running LOP brings the temps down very nicely of course.
Richening to 12 GPH will still get CHTs above 400F, take it up to 13GPH, and then they come into good control staying below 400F.
MY thought here is that pouring that much fuel into the engine is nearly the same thing as retarding the timing via slowing down the fuel burn. If I retard further, I should in theory be able to maintain the same performance at a lower fuel flow...
I wonder if my data is unusual or do others experience similar fuel flows to keep their CHTs under 400F?
I am interested in opinions on this. I was going to write this directly to Bill Repucci but realized others might benefit from the data and I am interested in others thoughts on this theory..
Randall Crothers
From Sedona, working in Northern California.
Recently I called Bill Repucci and he walked me through the steps to retard the timing in an effort to get CHTs more in control as they would go past 400F very easily. We reduced the timing advance by shifting the curve 2.8 degrees and this adjustment did make a difference. Now that I have flown this way awhile, I think maybe even more retardation is something to consider. I will post a savvy analysis plot of my recent light here:
https://www.savvyanalysis.com/flight/1493062/db5110c8-30ea-4bfd-b93f-9cda52ffecd2
Too bad the EI Commander can't be part of the data log posted above. I did not take notes on the flight, but remember seeing 23 degrees advance at full power at 4,500' with 80F OAT. The curve will advance up to about 30 deg. up at altitude with lower MAP. 23 degrees does not seem like much advance but reducing it by the 2.8 degrees did help so maybe even less advance will help more? That is my question.
The 2.8 deg. adjustment made my CHTs more manageable for sure, but I still have to dump fuel through the engine to keep them below 400F in full power conditions down low as the logged data from the flight shows.
Running LOP brings the temps down very nicely of course.
Richening to 12 GPH will still get CHTs above 400F, take it up to 13GPH, and then they come into good control staying below 400F.
MY thought here is that pouring that much fuel into the engine is nearly the same thing as retarding the timing via slowing down the fuel burn. If I retard further, I should in theory be able to maintain the same performance at a lower fuel flow...
I wonder if my data is unusual or do others experience similar fuel flows to keep their CHTs under 400F?
I am interested in opinions on this. I was going to write this directly to Bill Repucci but realized others might benefit from the data and I am interested in others thoughts on this theory..
Randall Crothers
From Sedona, working in Northern California.