@nton

Hi,

I have standart UPPIPE with NO CAT in it on Impreza STI 2002 EUR and I am going to replace ALL the exaust (header as well). Is it necessary to replace the UPPIPE as well? What for?

Thanks!

Dave T-S

Be careful - without introducing any other control, on this car decat from turbo back will result in 1.5 bar peak boost, adding an up pipe will result in 1.7 bar spikes

StephenDone

Having no cat in the up-pipe allows you to run leaner mixtures without risk of your cat burning up and your turbo attempting to chew it into little pieces. If it's got no cat in, then there's not a lot of point in swapping it - it's only extra expense really.

Bear in mind that some headers have the up-pipe built in too (for better flow and longer pipe lengths), so you may not need to use an up-pipe anyway. The Maxim Racing manifold is like this on the '99, though I haven't seen the '02 version yet.

Regs.

Steve

@nton

Thanks!
Will I resolve this issue (without introducing any other control, on this car decat from turbo back will result in 1.5 bar peak boost, adding an up pipe will result in 1.7 bar spikes) if install boost controller? Or it's not enough?

The possible aims of installing new uppipe are:
- to install EGT Sensor in new one as the old one is in cover.
- it should be wider than standart as well - or it's not necessary for me?

Razor2001

You can solve the boost spike problems cuased by uppipes and downpipes by playing with restritor sizes. Start with a 1.35mm and then work your way down till you achieve desired peak and held boost levels. Alternatively you can get a flow valve and install it instead of retrictor which will enable you to make adjustments in about 15 secs vs. having to wait for car to cool down and attacking the restrictor. There is a thread on the flow valve, do a search for it, think it is something like "flow valve instead of restrictor, excellent results" ....hmmm, sounds close

Cheers,
Ray