I have a 98 STi4 (300BHP) with Magnex rear box. I want to fit decat downpipe but also want to pass MOT. I understand the decat downpipe will leave me cat-less! Anyone tried this and passed?
Or is my only option to go for the power engineering high flow catted centre section? Does anyone else make one as they seem to be fiercly expensive? all answers appreciated.

 

Legally, you have to have a cat in order to pass its MOT regardless, even if you get better emmissions from not having any cats.

 

Ok well thats a start! Any further advice?

 

It takes about 15 minutes to put all your cats back in place.

 

I don't think a cat is a legal requirement. If it passes the emissions, what does it matter. Do STi4's have a centre cat as standard? if so you may, or may not pass the MOT with this. If you do have a catted centre, swap it for a Magnex none resonated item for £50. This will take 15 minutes to swap come MOT time.

 

You have to have one cat in a car to pass its MOT if its made after 1992.

 

STI4's dont have a centre cat and the rear has already been removed, hence my question.

 

It has a downpipe cat mate.

 

There are quite a few people who do sports cats. Power Engineerings is a sports cat centre. You can also get APS, MRT, Graham Goode who do sports cat in the downpipes. I believe milltek do one for all scoobs too, although I have only heard of them in conjunction with STi 7s. There are bound to be more.

I have a full APS system on my bugeye, from JW racing, not cheap but IMHO you won't find better quality, nice noise (quieter than most when cruising, very fruity on WOT). Big performance gains, but you'd get that with any good system.

 

Katana,

Only 1.6s, sports, turbos, P1s etc are listed for the Impreza. If your car is not on the list, it is tested as a pre '92 or is it '73? car, NO cats required.

It worked for me (STi5) and a few others I know.

 

What would you guys say a decent bit of power from an exhaust would be?? i.e full system with and without cats?

 

hypoluxa, looks like I'll be changing MOT stations if thats the case.

But if I recall correctly, it was written somewhere that imports do require a cat too. And the fact that I almost failed my emission test on my previous WRX with one cat (downpipe) means that I should have a cat anyway.

 

Check the V5 - if it doesn't state exactly what it is (normal if it's not an EU model) but instead says 'rear axle blah blah' then it doesn't need a cat & comes under the same 'heading' to the MOT testers as a pre-cat car. As which it should sail through.

 

i seem to remember that import cars are emissions exempt on mot tests or something like that. Anyway mines fully decat as are a few friends and we all pass no problems

 

Mines fully decatted (MY95 WRX) and it won't pass emissions without me putting the original exhaust back on for the test.

Tried to blag it on Saturday with the de-cat exhaust and it failed MOT on it. I usually swap it anyway but thought I'd give it a go..... Imports definitely need to pass emissions tests to gain MOT

 

They need to pass an emissions test, but not the same one as the cars with catalysts.
If the tester thinks you need a cat with an import, ask them to look up the model in their little book. They won't be able to find it, which means they do the 'standard' test, which means a cat isn't needed.
Although I think it makes a difference with the age... STi V doesn't need it (I don't think) so anything prior would be OK as well.