Detonation...

[RAYDEO]

During the trackday at ruapuna i found my car was Detonating up the stright...

what causes this and how do i fix it?

im asuming one of the causes is the fuel? 98

[Guest Fastfour]

Detonation......

Straight

Assuming

haha spelling nazi

[RAYDEO]

yeah ok... but you knew what i ment...

[99GTB]

Was most likely doing it round the whole track but could definitely hear the detonation as you boosted past the pits, did not sound good, could have been the reason your previous motor blew also.

[MINTGTB]

ouch.. you really do look after ya car(s) well Ray

[Guest loren]

crap, a whole track day of det... not good at all.

just use avgas on the track, I have always had to, even with a tune that doesn't det

on the dyno or street or hillclimbs etc.

[Guest]

 RAYDEO said:

During the trackday at ruapuna i found my car was Detonating up the stright...

what causes this and how do i fix it?

im asuming one of the causes is the fuel? 98

It's an uncontrolled explosion in your cylinders.

less boost

less timing

better fuel

better intercooler might help

[RAYDEO]

 Qwerty said:

less boost

im only running factory around 15psi...

[RAYDEO]

 99GTB said:

Was most likely doing it round the whole track but could definitely hear the detonation as you boosted past the pits, did not sound good, could have been the reason your previous motor blew also.

yeah it was detonating before the rebuild... just cant work out why...

[Guest keltik]

So you rebuilt it without fixing whatever made the first one go bang....not the best judgement there

[subieboy]

I say this is a perfect excuse to do the split fuel rail you always wanted... ;D

[RAYDEO]

 keltik said:

So you rebuilt it without fixing whatever made the first one go bang....not the best judgement there

my builder said it was possibly det because of the buggered piston, this is the first time since the rebuild I've been on the track and because I dont know what im listening for its hard to know when it is fixed or not...

[dubbedup]

det kinda sounds like coins being thrown down a steel pipe....

[RAYDEO]

they are new... what ever is factory genuine subaru for a V5 sti

[Koom]

Have you checked that the vacuum line to the fuel regulator is still attached?

The fuel pump could also be dying.

Could be alsorts causing it.

Do you have a breather bottle or still using the factory breather system?

[Guest boostin]

Dying AFM's are a leading cause too.

[RAYDEO]

everything is stil factory...

[Guest]

If stock then check the obvious as said above AFM / Fuel supply.

Std AFR tune for Sti's is usually on the safe side.

[RAYDEO]

cool. how do i check the AFM?

im assuming chucking a walbro 500hp pump is overkill? what else in the fuel supply can i check?

[99GTB]

Check the afm by borrowing a good one.

[RAYDEO]

 99GTB said:

Check the afm by borrowing a good one.

uhhhuh, and assuming mines buggered what difference should i notice?

i mean my car runs fine now around town... so do i borrow one for the next trackday or....?

[Guest boostin]

You think it runs fine now. It will most likely run better.

[Guest]

Put the car on a dyno and get the air fuel ratios checked. Way way cheaper than a rebuild.

If the afr's are way off you will know whats causing it to det.

If you can, get a replacement AFM to test if needed. Then if a different AFM solves the problem you know what needs replacing.

If the AFRs are still bad fuel pump is the next logical place to look. Not sure if you have replaced the fuel filter ? another possible.

Remember these cars are getting old. You can also check what sort of voltage is getting to your fuel pump.

Ver 5 AFM's are well known for dieing especially with aftermkt filters. But even everything stock they die. Some experts think you should replace them when you do the cambelt.

Since det + tracks can kill your engine its not something i'd do testing for det.

[Solja]

if you cant burrow a spare afm. try some afm cleaner you spray it onto the afm sensor its available butler automart stanmore rd see if that helps otherwise replacing afm may be only option, reguarding walbro 500hp intank id consider it a must if your ever replacing factory fuepump and can afford to do, if both these options dont sort the det id suggest getting it on a dyno for hour or two or at least to someone to check

[RAYDEO]

im going to try those soulitions, but ive just been tlaking o my builder and hes got me wondering if i have the correct ECU in the car... its only runs 15psi... so im not sure...