MK5 Golf GTI

All Things Mk5 => Modifications & Technical Area => Performance Modifications => Topic started by: craig_t on February 17, 2011, 09:45:57 am

Title: Pipwerx downpipe bottleneck??
Post by: craig_t on February 17, 2011, 09:45:57 am

I know fitting and a diwnpipe to stock cat back has been covered, but if I fit my 3" downpipe to stock cat back will having a reducer bottle neck the extra gases flowing threw the downpipe.

I know a few people have the same sort of set up and have felt good results, it's just after emailing a few garages on fitting this, they have mentioned it would not be a good idea without a 3" all the way through.

Title: Re: Pipwerx downpipe bottleneck??
Post by: vRStu on February 17, 2011, 09:51:03 am

I say do it.

One of your biggest bottle necks is in the Cat.  The aftermarket Cats are generally 200 CEL race/performance Cats.

Title: Re: Pipwerx downpipe bottleneck??
Post by: craig_t on February 17, 2011, 02:25:44 pm

Yeah it has a 200 cell.

I keep reading that a 3" down pipe is better on ko4 rather than the smaller ko3 that I have.

Title: Re: Pipwerx downpipe bottleneck??
Post by: muckipup on February 17, 2011, 04:15:58 pm

I can assure you that a 2.5" cat-back will have next to zero detrimental effect over a 3" cat-back when a 3" dp is used

PS and fyi - my car threw a rear lambda CEL with the Pipewerx dp and Stage 2. It was a false cat inefficiency CEL caused by the rear O2 sensor picking up the different flow characteristics (passed MOT emissions test by a long way!). Others have been luckier and I haven't heard about it with Milltek 2.75" dps. I have since changed to Revo software and they map this inconsequential CEL out as standard from Stage 2 on.

Title: Re: Pipwerx downpipe bottleneck??
Post by: Janner_Sy on February 17, 2011, 05:27:37 pm

do it, i had ther pipewerx DP and its very good.  As for saying you need a 3" DP, 

Dan GB has a 2.75" on his GT28 big turbo TFSI running 400Hp+

Title: Re: Pipwerx downpipe bottleneck??
Post by: craig_t on February 19, 2011, 10:11:16 am

Thanks for the info guys  :happy2: