Even if you did detect one, you've got very little time to do anything before something bad happens, if the engine is an older block, I think.



B

yep, less room for error on the older ones

That is true, but its part of the tuning process, to slowly roll into your tune, thats how you buy engine life, as John Cleese so aptly said, you just dont go stampeding for the clitoris, you start with a simple kiss..

Some things just happen, while others are avoidable, running really rich mixtures, weak ignitions , bad wires etc etc, that stuff is avoidable..

Typically though misfires will show and you can back out, 99% of the time its not where its a totally one shot happening that destroys the motor like detonation. Sometimes you cant even hear the misfires especially at rpm, but it will show with the tools I listed previouly, and contrary to popular belief it will show as a small torque drop then a large torque rise and the back to the mean output. But do it repeatedly and even an FD engine will succumb to misfire damage.

I know nothing of boosted engines, but isn't a flattened apex or corner seal spring, often evidence of a cycle of detonation?



I cracked out a front dowel hole years ago in a NA 12A with a cross fire. If you have a misfire, does the fuel air unspent and entering the turbo make the turbo more effective long enough to see the boost increase you have now?



I have misfires in NA 12A bridgeport any time the plug gap gets above .012". I set them at .010" before the race. This is with a MSD-6AL on both leading and trailing, with no split at all.



Another thought: in the definition of detonation is the part about "remote from the spark plug"........the split timing fits right in there.



Is there a possibility that the waste gate piping is seeing some harmonic in the primary pipe that is impeading flow and replicating a closing waste gate?



At the RPM where you are having this problem, the rotor face is moving very slowly. (compared to a piston moving over TDC) or dwell time. The time the rotor is at TDC is adequate for complete combustion and then some, with very little ignition advance.



The hair on the back of my neck is telling me that the boost spike is jacking the effective compression ratio up into the range where only a few degrees of advance can be tolerated.



Is there knock sensor in that data stream?



Lynn E. Hanover

i agree its either detonation or misfires, or possibly a little of both...

i hate flattened corner seal springs.. always a good indication of detonation.. engine looked flawlessly cleaned for a 2 year build..

Detonation as per the text-book definition of a second flame front post-spark event? That could be I figure as I was running well past 10:1 AFR's when it happened. My guess was that it was spark blow-out that created misfire then the shake-the-hell-out-of-the-motor thing.



B