jprelude92

we were street tuning the car with the tuner on the highway the car was driving fine my wideband was showing that i had enough fuel it was at 11 at wide open throttle i'm trying to find out what caused this i cheched the injectors and they all work.

welfarepc

pre-ignition by the looks of it

how much timing, what octane fuel?

jprelude92

timming was at 30 degrees and i was using 93 octane

boostedEF91

that seems like alot not??

jprelude92

timing was at 30 base i dont know where the tuner has the timing at on his lap top

tepid1

All on the intake side.... look like pre-ignition as well.

New pistons, new tuner and try it again. Obviously the tuner has no idea what their doing.

jprelude92

well what i'm thinking is that the tuner mess up i just had replace the head gasket a 1 month ago when he was tuning the car he made it detonate and it cracked the head gasket around the fire ring and also on top of the pistons was pitted on the intake side of the valve.

kyden

why was base timing at 30?????? your tuner sucks.

Scott_Tucker

Pre-ignition shows up as pock marks all over the top of the piston. When the rings lands are melted like that on the edges of the piston, that's detonation.

jprelude92

i dont know why the timing was at 30 thats where the tuner had it at

jprelude92

so what would cause detonation ?

oneludesol

is it even possible to get 30 degrees base?

boostedcivicsir

pre ignition is a case where something physical (i.e. hot spot carbon) causes the a/f mix to light before it is supposed to.

detonation is caused by lack of octane, overly advanced ign timing, or too much boost causing the a/f mix to destabilizt and light on its own.

with that, detonation is caused by, lean mix, over boost, lack of octane, too much timing, or any combination of the 4.

I CRX I

it may have been 30* at MBT, not base timing.

Bugermass

you got that backwards..

tepid1

Exactly. lol

I CRX I

what can cause pre-ignition? debris? tuning? more specifically, what are the main causes?

rorik

"Preignition" is caused by carbon build up, too hot of a spark plug, sharp edges on the piston, etc. That's not what did it here though.
I hate that term, because it does not specify if the "pre" is from an early ignition spark, or a hot spot. lol. But either way, obviously, pre ignition will cause detonation under high load conditions, since if it lights the mixture too early, that's the same exact thing as having too much timing advance.
Looks like all that happened here was that, too much timing advance, just like everyone said. Although I remember a thread a few years ago about where quite a few people had this happening with cp pistons on supposedly good tunes..

I'd smack the tuner upside the head with the laptop.

Turbo-LS

iTrader: (4)

thats detonation from to much ignition timing on a lower grade fuel. if it was 91-93 octane its easy to detonate without the porper tuning knowledge. a little to much timing for a long period of time aka a few back to back pulls will result in what you see in the pics.

new pistons, a real tuner and geturdone right

esedulerp5tenin

wait, whats the difference between pre-ign and detonation? i was under the impression that they were synonymous.

rorik

Depends how deep you want to look into it.

Bugermass

they are definatly not the same thing and they happen for different reasons completely as well as at different times during the engine cycle.. most peoples idea of what detonation and pre ignition are is incorrect and or incomplete.

cibao2ner

wow that is messed up!! i cracked a sleeve on my oem bottom on 10psi...but my pistons were mint no sign of detonation like that..those are melted and they are forged..you tuner should not be touching timing on a street tune..you can't measure the power difference while street tuning..he should have left timing slightly retarded and gotten your fuel right and then taken you to the dyno and play with the timing..

94GSRMR

u cracked a sleeve on 10psi? what motor? what turbo/trim?

Turbo B18C EJ6

30 degress advance is wayy to much i know on my setup it was set at 16 degres btdc then neptune adjusts it from there.