Help needed with emissions testing for MOT

[WilliamBodie65]

Hi everyone I’ve got a 2006 WRX running about 340bhp it’s got a sports cat on the downpipe with straight through exhaust with it being 2.5 inch diameter. On having my MOT the HC/CO levels were through the rough just wondered if anyone had any help with regards lowering emissions. Thanks for any help.

[Olivergt]

How did it pass last year?

There is a thread on here somewhere "Ask an MOT Tester anything", maybe worth asking on there as well.

But the real answer, which you don't want to hear, is you need to put a standard exhaust back on that will pass the emissions test.

[brillomaster]

If its got a sports cat on it'll need to be really hot. Book an mot, tell the tester to do the emissions testing first, and take it for a decent high revving drive just before you go for the test.

Failing that, either find a backstreet mot tester, or fit a proper cat for the test.

[WilliamBodie65]

This would of been the first MOT in my possession I only found out that the previous owner had hollowed out the cats when it went in for the MOT that’s why I put a sports CAT on.
I’ll make sure it’s boiling hot when it goes in. Unfortunately the back street garage seems to be a thing of the past nowadays which is a shame that would’ve been ideal for my situation. Thanks for all the advice much appreciated.

[WilliamBodie65]

Does removing the Air Filter prior to the MOT lower the emissions I’ve had a few people suggest this method ?

[geeks]

WilliamBodie65 said:

Does removing the Air Filter prior to the MOT lower the emissions I’ve had a few people suggest this method ?

I cant see how but I would advise against it all the same.

Also if your emissions were that bad it's possible even with a sports cat you aren't getting through an emissions test.

[Chris32345]

Probably need a better quality cat on the car most of these sports cars let airflow too quickly through them due to not having a fine enough mesh inside hence why they are "sports"

[steveo3002]

WilliamBodie65 said:

Does removing the Air Filter prior to the MOT lower the emissions I’ve had a few people suggest this method ?

seen it work on a borderline fail...isnt a miracle though

[E-bmw]

My baseline advice would be to start with the car as the manufacturers spent millions of pounds designing it.

Standard exhaust & an oil/filter service, then see what they say.

In real terms manufacturers are so good at designing sports cars these days that even a multi thousand pound exhaust system actually does so little it isn't worth it.

[stevieturbo]

WilliamBodie65 said:

Hi everyone I’ve got a 2006 WRX running about 340bhp it’s got a sports cat on the downpipe with straight through exhaust with it being 2.5 inch diameter. On having my MOT the HC/CO levels were through the rough just wondered if anyone had any help with regards lowering emissions. Thanks for any help.

"through the rough" is an unusual test measurement.

I presume they gave you actual results, which would be helpful for any attempt to recommend options

[tribbles]

stevieturbo said:

WilliamBodie65 said:

Hi everyone I’ve got a 2006 WRX running about 340bhp it’s got a sports cat on the downpipe with straight through exhaust with it being 2.5 inch diameter. On having my MOT the HC/CO levels were through the rough just wondered if anyone had any help with regards lowering emissions. Thanks for any help.

"through the rough" is an unusual test measurement.

I presume they gave you actual results, which would be helpful for any attempt to recommend options

Probably took it for a spin on the local golf course

[stevieturbo]

tribbles said:

Probably took it for a spin on the local golf course

At least the holes there are smoother and fewer than the roads !