Downpipe size, which is best?

[LaSarthe&Back]

Hi all, just wondering what is the optimum size for downpipes from KO3/KO3s turbo's with remaps running 200-230bhp.

Thought 3 inch may be better, as youu could shift gases out quicker, but is the 2.5" better cos it holds the back pressure better or what?? Little confused. . . any one who knows???

Also, would a Milltek sports cat be better over a Blueflame sports cat, as Jabbasport are trying to tell me that i want a Blueflame, and not sure if I do.

I want what's best for power!!!!!

Cheers,
Andy

 

[dummi]

bigger dwnpipe should help spool of turbo, the exhaust mani lends itself to faster spool with its narrw channels and is the real source of restriction

i have read on here over the past couple of years of problems with milltek sports cats but wait for replies to the thread before choosing..

 

[Stewart]

I dont think it was problems with Milltek CATs so much as they didn't derive any benefits at all and was proven on various dyno tests...

 

[dummi]

maybe i'm mistaken the issue of benefit has always been an issue but i thought i had read about a reliability issue maybe just my bad memory of the post

 

[nervus]

I remember posts about the milltek cats failing M.O.T's etc. Something to do with different specs like 100 and 200 cells or something. One passes the MOT and one doesn't or is difficult to make pass. Both are said to yield nothing in the power stakes with a standard turbo set-up.

 

[Stewart]

Ahh, just re-read the post and I would asume you have an A3 1.8T not an S3, apologies the comments about not making any difference were for replacing the S3's twin CATs.

On my golf 1.8T, changing the CAT for a Milltek sports CAT made a noticeable difference, louder for a start and more top end power...
The item that made the biggest difference was the 3" downpipe, much quicker spool up and lovely exhaust note.