I have just fitted a twin dump decat downpipe to my sti4. Before this, my boost gauge registered 1.4 then down to 1.2 at max revs.
It is now reading 1.6bar and 1.4/5 bar and max revs.
Is this going to cause damage to my engine/turbo? And if so, how to fix it?

Cheers guys

 

Anyone?

 

dont know how to fix it but 1.6 bar peak will be ok , but im not too sure about 1.5 bar top end will a boost controller not help you on this either manual or electric

 

Yes it will likely cause damage. I would run it at about 1 bar unless you have checked for knock and fuelling - ie knocklink or det cans and wideband lambda.

You can play with restrictors to adjust the boost. On your model year I think you need to increase the bore of the restrictor in 0.1mm steps to reduce boost. Get a set of fine drills from Maplin or similar, and don't use so much throttle that you ever go over 1 bar again until you've done it. I'm surprised you aren't cringing in the cabin from the really obvious detonation this is likely to be producing. Ouch, that could blow up the car in a few miles of hard driving. This all assuming standard ECU.

 

I recently had the same problem after fitting a twin dump downpipe. Tried to cure the creep with dawes and AVCR but no joy. I was told on here that the twin dump was causing the problem. I re-fitted the cat downpipe and problem solved, no more creep. I have just sold that pipe and purchashed an open neck pipe which so I am lead to believe will not cause the same issues.

Apprently it has something to do with the wastegate gasses interupting the flow.

 

I saw this once with a VF24 on an STi as well. Yet on other cars it has been fine. Easy way to tell if you have real boost creep is to disconnect the wastegate flapper. You should get no boost anywhere. I don't mean the actuator's pneumatic feed, that would give you way too much boost.

 

I have a STI 4 with a VF23 so could well be the same problem. I just connected a hose between inlet and actuator and still got creep rather than base boost.

I ran a 96 UK car before with a TD05 and twin dump but that was fine.

 

I've got boost creep on my 22b which has a VF23 and bpm twin dump. But AndyF mapped my AVC-R to keep it under control so it peaks where I wanted, at 1.3bar.

He mentioned cutting the splitter out of the DP may help the problem. If that doesn't work then he said porting the wastegate would resolve it.

From what I know, its due to the design of the twin dumps which does not allow the wastegate gases to flow efficiently, this makes the turbo boost 'creep' passed the level set as the wastegate can't dump enough air to stop it.

Dave.