Gear Head

iTrader: (2)

I have a sports cat downpipe fitted at the moment. If I leave the cat in the uppipe and decat the downpipe, will it pass an mot?

Also, is there likely overboost issues?

Matthew Gill

Mine passes with just the downpipe cat and I have 50% compression on #1 cylinder. I also ran without the up-pipe cat and an STI intercooler without any boost, emmision or det issues.

Comp was low before I fitted a de-cat and Intercooler before all the clique jump in! I thought sod it if it blows I have an engine in my bedroom. ...and before the snide remarks, I love everything scooby.

MichaelW

iTrader: (7)

Would you not be better off leaving the sports cat on and fitting a decatted up pipe? I think you'd probably notice more difference and you'd still have a good chance of it passing an emissions test.

Matthew Gill

+1

Removing cat from up-pipe is job number 1 on the WRX. Well, after you de-tango of course.

It doesn't get mentioned much in the UK but over in the US a lot is made of the extra power and spool gained and not to mention the piece of mind that bits of cat won't be going through the turbo and into the engine.

stonejedi

iTrader: (51)

+2 I have the prodrive performance cat down pipe on my car and it has never failed a emissions test.SJ.

Steve_PPP

iTrader: (3)

To answer the original question.... No, an uppipe cat is very unlikely to get you through an emissions test. Its tiny and doesn't do much.

If you decat the downpipe, you should remap too.

Turbotits

iTrader: (2)

Any cat missing regardless of emissions passing or not is technically a failure. but you'd probably be better of removing the up-pipe cat and leaving the sports cat in place.

Theres very few testers that would know if an up-pipe cat had been removed. Especially as the sti doesnt have one anyway

Matthew Gill

I think the cat can be removed from the pipe without welding etc, but I'm not 100%

just me

iTrader: (3)

SJ how much power is your car running? I had a look at your project thread, would you still be using the prodrive cat once your engine is built?

Cheers

stonejedi

iTrader: (51)

430 bhp as it stands,but No mate all pipe work is going to be changed.SJ.

just me

iTrader: (3)

All that through a prodrive cat!

Wow!! I think you just made my day!!!!!!!!!

stonejedi

iTrader: (51)

When i started to modify I researched and asked olley of RCM about the prodrive cat he told me not to worry about changing it as the prodrive one is good and I will still get good power just changing the rest of my exhaust which I did.SJ.

just me

iTrader: (3)

SJ thanks for that info, 400bhp here I come!!