Following from my previous supplier question, I now have another.

Is there a difference in performance, effectiveness or loudness between going for the cat in the down-pipe and having it in the centre section.

Thanks,
Martin.

 

I think a sports cat in the centre section is supposed to result in a quicker turbo spool up than with one in the downpipe.

Alan

 

...but if it's housed in the centre section, wouldn't it be more vulnerable to impact (from road debris etc)?

 

Cheers Gents,
I've never had any problems with the standard centre cat being damaged, so the decision may come down to cost.

Martin.

 

Performance - depends on what power you're running etc. Probably ought to be a little better the further down the system it is - i.e. centre section best. However, a good 3" sports cat at the bottom of the downpipe seems to make very little difference to cars with no more than 300bhp or so. IIRC someone independent commented (so this is second hand info) that the prodrive sports cat in the STi PPP didn't make a detectable loss with an ECUTEK map running 330bhp. Power Engineering claim their sports centre cat is no real restriction until ~400bhp, I don't know if anyone has independently proved this

Regards noise - if you have a sports cat downpipe, you can still have a resonator in the centre section, so you can make it quieter. I don't believe anyone makes a sports cat centre section that can also take a resonator. Of course, with a sports cat downpipe, you don't have to have the resonator, at which point the noise will be quite similar. By far the biggest factor in noise is usually the backbox, anyway.

If you're talking about the standard fit cats, the OEM downpipe is very restrictive, and replacing that will be a real benefit.