scoobylav

I am looking at changing my Exhaust to release more power. I don't want to have to keep changing the centre section to get through an MOT if possible. I was thinking of just changing the Downpipe (already have a Magnex backbox) will this give a reasonable if any increase in performance. If so will I still be OK for MOT as I will still have one Cat in the system.

nom

Yes, you'll get a performance increase. As for the MOT, results from just the centre section vary...

scoobylav

Vary ?????

So will it pass or not. I thought you guys with full decats change the centre section for MOT ????

scoobylav

Vary ?????

So will it pass or not. I thought you guys with full decats change the centre section for MOT ????

Johnny50

Hi Ian,

Is there not a cat on the downpipe aswell ??

i may be wrong, but i'm sure i've talked about this with someone before, and the scoob has two cats ??

As i say, i may be wrong.

Johnny

nom

There's a cat in the DP & centre. The DP cat is a full cat, the centre one is designed to 'mop up' any leftovers. Hence sometimes the centre one by itself manages, other times it doesn't... Technically, if it's in perfect working condition, it'll do the job itself - but these things wear out: if it's left in all the time, it quite possibly won't have a very long life. If it's only swapped back in for the MOT, there's a good chance it'll get though (that is if you've taken it for a good blast beforehand & it's really hot - cats only work once up to operating temperature, and being in the centre section doesn't help ).

scoobylav

Ok so would I be better just changing the center section ? Would this make much difference to performance or not ?

nom

Getting rid of the centre section won't make much of a difference in any direction.
The other possibility is getting a 'sports cat' - much better flow than a standard cat, and you only need one. The downside is the cost!

scoobylav

I think full decat is the way forward. So how do the guys with full decats get through MOT. I cannot believe that they all put a cat on for the MOT. Or do you just need to know an understanding garage ????

Johnny50

As far as i'm aware, people will swap the cats back on..as the garage is playing a big risk to pass the car without the cats on.

what would scooby do

Yup

Do full decat - don't worry about swapping stuff around..

Daz WRX

As you said they know an understanding garage or they do pop the cat back in for the MOT, no other options for a full decat.
I have replaced the centre sections and emissions are fine with the cat in the downpipe. Gains.. well H&S downpipe back system is 18bhp IIRC.

Daz.