Can motors experience detonation in neutral?

[dibbons]

I was curious whether a motor with too high a compression ratio for the gasoline available could experience detonation in neutral, either at idle speed or when run at a steady higher RPM like 2000-3000 RPM during first fire-up/break-in run? Thank you.

 

[RustyRatRod]

Yes.

 

[MoparLeo]

Why ? What happened ? Detonation could happen by numerous variables like high compression, mixed with excessive timing advance and low octane fuel. All or any combination. If you are concerned that you have caused piston damage due to audible detonation (ping), just do a compression or leak down test. Look at the spark plug electrodes. The next step would be teardown.

 

[72bluNblu]

If the compression ratio is high enough you can get detonation whenever. Idle, higher rpms, whenever.

Although, if you have detonation at idle you're WAY off on the compression for whatever fuel you're trying to run. Or the tune/timing.

 

[MoparLeo]

Exactly.

 

[dibbons]

No problems at the moment, but the non-running 318 I purchased a while back had one piston with a hole in the center, looked like a burn hole to me. But the other 7 pistons were not damaged.

 

[AJ/FormS]

A holy teener, eh?
Flip the head over and check the exhaust valve for that cylinder

 

[dibbons]

The motor was rebuilt, unfortunately can't inspect any more parts. Thank you.

 

[whitepunkonnitro]

Anything is possible, but to experience no-load detonation, something..engine temp, fuel quality, ignition timing..has to be very seriously out of the happy zone