R33 gts-t detonation above 4500

[Queppa]

Hey what up,
Ive got an r33 gts-t rb25det skyline with a front mount intercooler and 3 inch mandrel bent exhaust that pings then pops straight after at around 4500 then again around 5500 when your into it.
you here it pinging right before it pops and the whole car jolts when it pops.
We checked the fuel pressure while running it and it seemed to detonate when the fuel pressure dropped below 45.
se we clamped the return line to up the pressure to stop it dropping below 48 which stopped the popping but it was still pinging.
its got 87000 on it with new plugs k&N pod an new fuel filter.
interesting that with the air con on it makes the problem even worse.
fuel is vortex. no difference with octane boost either
Any Ideas.

[EricR33]

Originally Posted by Queppa

Hey what up,
Ive got an r33 gts-t rb25det skyline with a front mount intercooler and 3 inch mandrel bent exhaust that pings then pops straight after at around 4500 then again around 5500 when your into it.
you here it pinging right before it pops and the whole car jolts when it pops.
We checked the fuel pressure while running it and it seemed to detonate when the fuel pressure dropped below 45.
se we clamped the return line to up the pressure to stop it dropping below 48 which stopped the popping but it was still pinging.
its got 87000 on it with new plugs k&N pod an new fuel filter.
interesting that with the air con on it makes the problem even worse.
fuel is vortex. no difference with octane boost either
Any Ideas.

Stupid question but what does 'pinging' actually sound like ? You hear it from the engine ?

Eric.

[Queppa]

Pinging is the noise of the pistons slapping the side of the bores in the motor. it is also called pre-ignition.
You get hot spots on the pistons that causes the fuel to ignite before the spark plug intends it too and so you get a double explosion which causes the piston to be pushed in different directions. When the pinging gets bad, thats when the engine pops (or backfires if you prefer).

[EricR33]

Originally Posted by Queppa

Pinging is the noise of the pistons slapping the side of the bores in the motor. it is also called pre-ignition.
You get hot spots on the pistons that causes the fuel to ignite before the spark plug intends it too and so you get a double explosion which causes the piston to be pushed in different directions. When the pinging gets bad, thats when the engine pops (or backfires if you prefer).

Not all backfiring is caused by pinging of course though right >

Eric.

[Queppa]

no its not. the backfiring is caused by the wrong fuel and and air mixtures. not enough fuel and the extra air makes more heat and thats when you get the hot spots on the pistons that make it ping. Also timing will make it ping aswel. The cars goin on the dyno on tuesday though so then we'll see exactly whats happenin in the fuel and timing department.

Anyone know a cheap way of altering the original cpu without getting a new computer?

[ER34GTt]

Hi,
I have the same thing going on with My ER34 same engine as yours RB25DET...well mine does the very exact same thing but only in the morning...when its really cold outside...5mins after i first get of the road it will backfire once it drops below 4000 rpm range then hitting third and forth little hesitation during acceleration...hmmm I havent figured the thing out but...my advice to you is let somebody else with more knowledge handle to job. it might just be the fuel lowere octane, build up in the piping hot spots like they said ..who knows...

[Queppa]

Hey Guys,

I know its about 3 years late but heres the solution to the problem for any readers just loggin onto this thread.
The Pinging/backfiring/gunshot was caused by a combination of three things.
The crank angle sensor needed adjusting. (The it wasn't the main cause)
The spark plug gap needed putting down to .8 (again not the main culprit)
And there was a crack in the vacuum hose running to the wastegate.
So Boost was too high.
The Air flow meters are only good up to around 14psi. the boost was going over this and therefor the engine was running very lean, and thats why we were getting the massive backfire problems.
All sorted once the crack in the line was fixed.