pjc
Well Known Member
Seeking knowledge ...
I have an RV-6 with a 150hp (7:1 compression) O-320 E2D. Dual slick mags, L is 120 since new, R is 160 since overhaul. Champion REM40E plugs. Absolutely stock in configuration as far as I know. Engine is 980 SMOH (many years ago). Compressions were good at last annual 10 months and 60 hrs ago. Starts, idles, runs smoothly historically. Uses 1-2 quarts between oil changes every 40 hrs.
I have recently (about 30 hrs ago) began running 89 octane ethanol free auto gas for which the fuel system and engine are designed/approved. (Please don’t hate, it’s experimentation). At the last annual I switched from Aeroshell 100W to Phillips XC 20-50. I have not observed any operational changes with the fuel or oil switches. CHTs routinely 300-360F (depending on flight regime). Never seen any rapid CHT transients that might suggest detonation.
This weekend I got a poor mag drop (~250 rpm and roughness) on the R mag. Typical drop is ~75 rpm from both sides. L is still ~75 rpm. Engine was heat soaked on startup (had been sitting a hour or so) so vaporizing fuel was a thought/concern but doesn’t correlate well to one bad mag drop. Start up and run up on Both mags was unremarkable.
Investigation begun with plugs, which appear Ash (?) fouled (photo attached). The deposit is chalky (soft) and degrades to a fine powder when removed. All 8 were similar in appearance. Some were a little worse than the example in the photo. I have not experienced deposits such as these previously. Plugs cleaned re-gapped and re-installed. I have not re-confirmed static timing (25 BTDC) but intend to before a ground run.
What I was able to find using search suggests:
A). Possibly over-lean condition - this would be concerning (and unexpected)
B). Possibly ash deposits in the fuel (presumably the newly introduced auto gas)
C). Possibly ash deposits from burning oil (but oil consumption has been low)
D). Possibly ash deposits from oil additive package (although this experience seems to be from auto engines using auto oils).
Any thoughts about these theories, or suggestions about what is going on, diagnostics or maintenance to be performed, or operational tests or changes to be implemented?
Thx in advance,
Peter
I have an RV-6 with a 150hp (7:1 compression) O-320 E2D. Dual slick mags, L is 120 since new, R is 160 since overhaul. Champion REM40E plugs. Absolutely stock in configuration as far as I know. Engine is 980 SMOH (many years ago). Compressions were good at last annual 10 months and 60 hrs ago. Starts, idles, runs smoothly historically. Uses 1-2 quarts between oil changes every 40 hrs.
I have recently (about 30 hrs ago) began running 89 octane ethanol free auto gas for which the fuel system and engine are designed/approved. (Please don’t hate, it’s experimentation). At the last annual I switched from Aeroshell 100W to Phillips XC 20-50. I have not observed any operational changes with the fuel or oil switches. CHTs routinely 300-360F (depending on flight regime). Never seen any rapid CHT transients that might suggest detonation.
This weekend I got a poor mag drop (~250 rpm and roughness) on the R mag. Typical drop is ~75 rpm from both sides. L is still ~75 rpm. Engine was heat soaked on startup (had been sitting a hour or so) so vaporizing fuel was a thought/concern but doesn’t correlate well to one bad mag drop. Start up and run up on Both mags was unremarkable.
Investigation begun with plugs, which appear Ash (?) fouled (photo attached). The deposit is chalky (soft) and degrades to a fine powder when removed. All 8 were similar in appearance. Some were a little worse than the example in the photo. I have not experienced deposits such as these previously. Plugs cleaned re-gapped and re-installed. I have not re-confirmed static timing (25 BTDC) but intend to before a ground run.
What I was able to find using search suggests:
A). Possibly over-lean condition - this would be concerning (and unexpected)
B). Possibly ash deposits in the fuel (presumably the newly introduced auto gas)
C). Possibly ash deposits from burning oil (but oil consumption has been low)
D). Possibly ash deposits from oil additive package (although this experience seems to be from auto engines using auto oils).
Any thoughts about these theories, or suggestions about what is going on, diagnostics or maintenance to be performed, or operational tests or changes to be implemented?
Thx in advance,
Peter