cast iron

Full Load "pinking"

7 posts in this topic

rebuilt last years race engine with all but the old knife edged and lightened crank, same compression rods pistons cams and head, put the original map back in and its pinking / knocking badly at full load from around 3K. Lift to part load or change down and its fine.

What can have changed to cause this?

I can only think that the standard heavier crank wont spin up as quick?

The TPS values are spot on, strobe shows the timing to be pretty good.

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fuel or thinner head gasket maybe

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Sounds like it's detonating.

Maybe requires a different AFR or ignition timing to stop the detonation - if you have a vacuum leak, injector gone out of spec, fuel pump/filter/regulator/different octane fuel (or older) etc all could cause it.

If you have overbored the engine this will increase compression as will a change in cam timing.(I appreciate you do say same pistons)

Spark plugs too 'hot' - have you changed plugs to a 'hotter plug'?

Anything that slows down the turning of the crank will keep cylinder pressures higher for longer and can instigate the 'second' burn.

Unless you stop it you will damage the ring lands on the pistons very quickly.

- needs a re-map urgently.

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Hi Fraser, I know what it needs, just like to know a reason why:) Nothing changes without a reason. If I could find and fix the cause I might avoid a remap. Oh well off to the rollers with her

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If you can access the map then reduce the ignition timing. Failing that. Higher octane fuel.

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If it wasn't so wet I was going to go out and play. Will just do the geometry today. Local rollers booked for 21st :)

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Well a turn up for the books, perhaps i didn't fully explain the situation, which doesn't help!

The car was overheating yesterday 105 degrees, this morning i bled the system cold, ran it at tick-over up to temp, bled it off again, now the temp is pretty solid at 90 degrees in all conditions and it doesn't pink!!

Still going to get it checked over on the rollers and wont be thrashing it just yet

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