Cliff notes: for the past few weeks, I noticed that my cylinder #5 is pulls timing pretty regularly, often pulling 6-9 degrees of advance.
Things I've tried:
Setup FBO, Cobb V3, 455LPH LPFP, e50-e85 (depending on trial).
I normally run E70 and have tried going to e50 to bring HPFP up and it is still chatty. I even went so far as to set timing to 8 degrees flat, and this is quiet but number 5 still pulls a few degrees from time to time. The other cylinders are typically quiet. Lastly, I went full 100% e85 and #5 still pulls timing progressively, on a moderately aggressive tune (9-10 deg in midrange ramping to 13.5 at 6k).
I've done compression tests, as recently as this weekend: on a cold engine, all cylinders read 150psi with 8 cranks, 115-120psi on 2 cranks, and 90psi with 1 crank. They are read the same which is good. Looking at the plugs, my #2 smells like fuel (prob leaky injector), but the rest are good.
Following the compression test, I cleaned all plugs and moved the coil and spark plug from #5 to other cylinders to rule those out as culprits.
At this point I'm out of ideas and looking for advice or possible theories. Does this truly appear to be knock? The only thing I've changed recently, is I went from Cobb V2 to V3, which likely doesn't matter (the maps have to be regenerated and re-loaded).
Here are some logs:
Things I've tried:
- e50, e70, e85
- Run only 8 deg advance
- Compression test
- Swap plug and coil for #5
- Test ethanol of fuel (reads exactly 85% ethanol)
- No codes thrown
Setup FBO, Cobb V3, 455LPH LPFP, e50-e85 (depending on trial).
I normally run E70 and have tried going to e50 to bring HPFP up and it is still chatty. I even went so far as to set timing to 8 degrees flat, and this is quiet but number 5 still pulls a few degrees from time to time. The other cylinders are typically quiet. Lastly, I went full 100% e85 and #5 still pulls timing progressively, on a moderately aggressive tune (9-10 deg in midrange ramping to 13.5 at 6k).
I've done compression tests, as recently as this weekend: on a cold engine, all cylinders read 150psi with 8 cranks, 115-120psi on 2 cranks, and 90psi with 1 crank. They are read the same which is good. Looking at the plugs, my #2 smells like fuel (prob leaky injector), but the rest are good.
Following the compression test, I cleaned all plugs and moved the coil and spark plug from #5 to other cylinders to rule those out as culprits.
At this point I'm out of ideas and looking for advice or possible theories. Does this truly appear to be knock? The only thing I've changed recently, is I went from Cobb V2 to V3, which likely doesn't matter (the maps have to be regenerated and re-loaded).
Here are some logs:
- e85 5th cyl pull only http://www.datazap.me/u/ghost/204-e8...-9-11-12-13-15
- e85 5th cyl pull only (zoom to first few seconds) http://www.datazap.me/u/ghost/202-e8...7-8-9-11-13-15
- e50 only 8 deg advance http://www.datazap.me/u/ghost/143-m3...-9-12-13-15-17
- Here is an e65 1/4 run a couple weeks ago that is pretty clean (AP V2 FWIW) http://www.datazap.me/u/ghost/44-132...-9-12-13-15-17