Rb25 Over Boost Problem Need Help Asap

[lozz_ti]

Hey guys my rb25 is over boosting for some reason on the standard Ecu. It gets to approx 8psi and I can here the gate open then there is a huge flat spot and the boost slowly creeps up to 15psi once it gets to 15psi the flat spot clears out the boost hits 22psi and hits like a early limiter/boost cut.

I fitted my brother's nistune Ecu and the car goes great no flat spot, gate opens at approx 8psi and it makes 9psi tops on my boost gauge. So at this stage I thought the Ecu was stuffed. Got another standard Ecu and fitted it. It was the exact same as my standard Ecu. I have also changed air flow meter and I have replaced the cas. I have run out of ideas as to why it over boosts and has a massive flat spot with two standard Ecu's fitted to it but not with the nistune?

Any body experienced this before? I need to fix this problem asap

Any help would be greatly appreciated!!

Cheers, lozz

[lozz_ti]

Also I disconnected the actuator from the waste gate flap so the gate was open fully open and it was still able to over boost with the standard Ecu. It's really got me confused that it can over boost with the stock Ecu and not with the nistune

Cheers, lozz

[Ben C34]

That's weird. Are you running a screamer dump pipe? how can you hear the gate open?

[scotty nm35]

Stock dump? I have only seen this happen with split dumps.

If the engine is going into rich and retard, the extra fuel dumping and timing backed out will help cause the overboost.

[89CAL]

As above

It's the stock ECU. Get a Nistune/Power FC/ Link etc and get it tuned properly

[gunt_116]

Did have split dumps. But now has a chinese cheap turbo with vband with wastegate inside. Just wants to use standard ecu not aftermarket and get it tuned etc..

[GTSBoy]

Um. Stupidity is happening? Random Chinese turbo + std ECU do not match. If much more airflow is being generated by the turbo than the ECU is happy with, then R&R and other bullshit will occur and happiness will be = zero. Proof of pudding seen by transplanting in Nistune ECU. Get rid of the turbo or get rid of the std ECU.

[gunt_116]

Was doing the same thing on standard turbo though? Except not boosting so high but still overboosting. This turbo was said to be direct swap over nothing else needed to be changed.

[Ben C34]

wow. the plot thickens

[KiwiRS4T]

Was doing the same thing on standard turbo though? Except not boosting so high but still overboosting. This turbo was said to be direct swap over nothing else needed to be changed.

They lied. You can't tune a stock ecu - get a Nistune chip/

[lozz_ti]

As said it was doing the same thing with the standard turbo but not over boosting as bad. It did have a split dump pipe On it it with the screamer returning back to the exhaust but you could here how loud the car was as soon as the gate opened and there being a massive flat spot it started to sound like a Holden red motor with no exhaust going up a big hill. The standard turbo let go do to over speeding. Put another second hand standard turbo on that the guy promised was mint and the oil seal exhaust side was buggered being the only reason I slapped the Chinese unit On and if I could get it running right I was going to put a decent turbo, Ecu, injector, etc... But really just need it going for now

[89CAL]

Are you sure there isnt a problem with the wastegate line or a boost tee etc that you dont know about?

A leak in the wastegate line will cause overboosting. If you'r stock turbo blew up due to overboosting and now your still having overboosting problems then I would check there is nothing wrong on the wastegate vac line side of things.

Running the stock ECU with any bigger then stock turbo is still not a good idea. The car will run horribly. Even stock turbo with extra boost can be bad. Mine wouldnt run any more than 8psi with stock ECU, would just hit a massive cut in the tune and the car would jerk and then go again. It also had horribly rich AFR's (10:1)

We aren't trying to make you spend more money. Most of us have all been there trying to get the stock ECU to do something it doesnt want to do. They are usually more forgiving on R32's but still sometimes throw problems up

[lozz_ti]

Thanks for the info guys I ended up buying a the nistune I borrowed. The New turbo came with a new hose it went straight from the compressor housing to the actuator. It really just had me confused that the standard Ecu could make it over boost and build up to 22 psi and the nistune wouldn't build anymore that 8-9 psi

[Dose Pipe Sutututu]

Sounds like timing might be off for whatever reason, like full retarded to build that kind of boost.

Not half retard, full retard lol..

Still doesn't make any sense, but hey your car is running

[Ben C34]

You never go full retard!

[Cyifly]

Thanks for the info guys I ended up buying a the nistune I borrowed. The New turbo came with a new hose it went straight from the compressor housing to the actuator. It really just had me confused that the standard Ecu could make it over boost and build up to 22 psi and the nistune wouldn't build anymore that 8-9 psi

There has been a few guys I've neg with standard ecu's runnin 20 - 23 pound boost. Don't ask me how ..

Just happened to be what they were running. They ran rough though apart from wot. Would have gone way better had they spent the money on an ecu