Tom @ N269CP
Well Known Member
I had a local service shop replace my left magneto early this week (Slick 4371 IC mag). On my first post-work flight I noticed the cyl # 1 EGT climb to possibly over 1450F with Cyl #1 CHT of 425F...other three cylinders were lower and comparable to each other...only the Cyl #1 temperatures spiked. During the left mag drop test the rpm dropped by about 120 rpm. The planes climb rate was definitely sluggish compared to normal climbout. I normally take off full rich as the plane has bags of power and it helps keep my CHT's below 400F.
Today the workshop checked the magneto timing which he found to be 30 deg BTC versus the Lycoming spec of 25 deg BTC. The discrepancy appears to have been caused by an internal mag timing error which the shop set while installing the mag, compounded by their not electronically confirming the advance....timing appears to have been set solely off the flywheel timing mark..which is wrong if the mag internal timing was wrong to begin with.
Static manifold pressure at my home airport is about 24.5"Hg. Takeoff RPM is 2650 rpm....this puts the takeoff power at somewhat over 75% (24/24).
My question for VAF is this: Could this 5 deg advance timing error have resulted in detonation during takeoff which may have caused the higher than expected EGT/CHT?
I'm hesitant to fly the plane until I better understand the potential for detonation damage...may have another shop borescope the cylinders Friday morning before flying it anywhere.
I would be grateful for any suggestions as to my next course of action. I'd rather be safe than sorry.
Today the workshop checked the magneto timing which he found to be 30 deg BTC versus the Lycoming spec of 25 deg BTC. The discrepancy appears to have been caused by an internal mag timing error which the shop set while installing the mag, compounded by their not electronically confirming the advance....timing appears to have been set solely off the flywheel timing mark..which is wrong if the mag internal timing was wrong to begin with.
Static manifold pressure at my home airport is about 24.5"Hg. Takeoff RPM is 2650 rpm....this puts the takeoff power at somewhat over 75% (24/24).
My question for VAF is this: Could this 5 deg advance timing error have resulted in detonation during takeoff which may have caused the higher than expected EGT/CHT?
I'm hesitant to fly the plane until I better understand the potential for detonation damage...may have another shop borescope the cylinders Friday morning before flying it anywhere.
I would be grateful for any suggestions as to my next course of action. I'd rather be safe than sorry.
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