Holes in the Pistons are PRE IGNITION, very harmful stuff...not necessarily caused by running lean, but can be.

 

yeah, what are we talking about as far as lean mixtures that can put holes in pistons? 18-19 a/f ?

 

Depends on the cylinder pressures. More pressure = more heat on compression.

 

would this be what is happening when you are hauling *** then let off the gas?

because i had to do that for a speed trap and i thought my ---- was going to blow.

full vacuum but like 21 afr.

 

No, that's injector cut...basically the engine starts to act like a giant air pump when decelling and off the throttle.

 

Pre-Ignition is NOT detonation. They are two entirely different phenomena.

Detonation is a second ignition after the spark plug has already initiated combustion.

Pre-Ignition is ignition before the spark plug has a chance to do it, which is WAY WAY more harmful than detonation. Pre-Ignition is a combustion event that totally works against piston travel, kind of like the worst case of advanced timing. It happens because when the piston is at BDC, the pressure in the cylinder is very low, thus any fuel inside is really easy to ignite, but has a slow flame propagation. Any hotspots in the cylinder could ignite the mixture.

 

that bad?

 

when the injectors cut off you get no fuel. vacuum volumes of air and no fuel, sound like a possibility for detonation to you?

it's normal.

 

No, think about it.

You need fuel to have any form of combustion. Without fuel, you can't have normal combustion, detonation, or pre-ignition.


Fuel cut is a rather harsh way to cut engine speed though. Ignition cut is way way softer.

 

you cut fuel every time you let off the throttle