I've searched but didnt really find a exact answer I was looking for.

I just installed a tanabe downpipe on a stock cat last night.
The car already has a 3in exhaust.

Took the car out for a drive afterwards and this is what happens.
Pull on 4th gear, the boost spikes to almost 1.5bar and comes down to 1.3bar then slowly creeps back to 1.4 bar.

Am I experiencing boost creep or is it because I have the stock cat on there?
I've checked to make sure there are no leaks from the downpipe (no ticking or gas noise).

The car held boost at 1.4 bar perfectly when I had the stock downpipe.

Any suggestions/help would be appreciated.

Thanks.

 

Doesn't surprise me. I'd reset the ecu. If it still happens, I wouldn't worry about it.

 

Well I just installed my boost gauge on Saturday finally and now see how my car has been running the last year. I spike to 23psi!!! All I have done so far is a 3" catless TBE and no tune. It makes sense though. Less back pressure. But I was very suprised to see it spike THAT high. I would say the less restrictive dp is the problem. Do you have a MBC???

 

That is not boost creep.

Boost creep is when the boost keeps rising due to the inability of the wastegate to get eenough exhaust gas out or bypassing the exhaust side of the turbo; this could also be because of the physical aspects of the manifold or hotside being to small and the wastegate being sufficient etc.

what you have is a spike.

 

A little spike to 1.4bar then to 1.3 and then back to 1.4bar is ok I am assuming?

BTW, I do have a mbc.
I turned it down to 1.4bar because it boosted to 1.5bar after the downpipe install.
The ecu was resetted too.

 

yes you may have to adjust the MBC with the addition of new parts etc; a spike and then drop to a steady psi is fairly common. As long as that is where your tune is you are fine.