I know this has been done to death (well nearly) but heres a quicky...

The general opinion seams to be that a de-cat d/p is good on any car; turbo spool-up time and possibly better flow at high rpm.

Will you see a much bigger benefit if the middle cat is removed as well? Do you need this to see a benefit with the d/p?

On a UK turbo is it worth spending on a branched d/p or a simple straight through?

UK has smallish turbo as I understand it and so the branched type may be overkill.

James

On UK (cars which have a centre CAT) there is a marked difference in adding a throughpipe - not in outright power but in throttle response & low down torque (I had one on my last UK car)
On STi's there is no centre CAT on V5's.
On V4's some were made with centre CATS(earlier cars)- some without (later cars)
V3's or earlier did have centre CATS I believe.
I am actually fitting a centre CAT replacement pipe to my V4 STi this weekend (I am not sure if mine does or doesn't have a CAT though !!) - so I will let you know of any differences it makes.

Not sure on the branched downpipe question - other than the ScoobySport Downpipe seems to be the favorite at the moment.

Ro

James.

I have just fitted a d/p to my UK car making it completely cat-free.
The difference it made losing the other cat was as big as when I first swapped my original exhaust for my Scorpion!
I have been surprised by the gains, and my d/p was a simple design like the original but no cat, i.e., no extra pipes or wider flanges.
I don't know if those help on a UK car, but I think the SS one has a wider flange. It will make a difference getting rid of just one cat, but I'm glad I'm now cat free....if only for the noise! http://bbs.scoobynet.co.uk/biggrin.gif

Stef.

RoShamBo

Whilst there is no centre cat on the STi5 pipe, the middle silencer is actually know to hinder performance. Therefore changing the std STi5 centre pipe to something like ScoobySport or Magnex does provide gains in its self. This is exactly what i am doing this weekend.

James, i will let you know the improvement this weekend as i have a UK MY99 with SS Downpipe and SS Backbox, with the STi5 centre section. This is going to be swapped for the Magnex deccatted pipe.
I have the open SS Downpipe and it makes a big difference...but i would also imagine similar things from the twin dump design from MRT etc. At the end of the day, any decatted pipe will provide good gains and if there is a distinction between the two, u may not notice it unless you highly tune your engine....u pays yer money and takes yer choice.
I would imagine that the centre pipe replacement will provide a good gain on your car too, especially if the rest of the exhaust system is free-er flowing.

I paid 112 quid inc delivery for my Magnex Pipe from Falkland Performance in Scotland. The reason i bought this as opposed to the SS centre section is that the SS centre section has no resonator to help calm the noise.

Watch this space!

James,
I did some testing on the mid-section of my STi5 at PE.
Even though the STi5 doesn't have a mid-section cat (just an expansion box), this box is restrictive!
You get good gains in torque by cutting out this box and having a straight through pipe.
Pete Croney can sort you out with a replacement for less than £50.

See the improvements on the dyno site :-

I'm sure one of the boys at the last PE dyno day said he lost power when he took the centre CAT out....so he put it back! Can't remember his name, but he had a STi, red hair and was wearing a blue 555 coat.

Wierd!

It worked wonders on my car anyway!!

Gethin
MY97 WRX

NeilR was the individual i think ...maybe his car was running too lean or sommit after?

If you see Paul Strongs site, most people have got very good gains in the midrange from doing the swap.

[This message has been edited by sunilp (edited 28-01-2000).]

Well got my Magnex centre section put on at SS today (eventually!) and this replaced my STi5 centre pipe....definetely MUCH more grunt around 3500 rpm onwards......pushes you back in your seat nicely

Do it!

I also had my centre pipe fitted yesterday.
Slight increase in mid range - not a great deal though (I wasn't expecting there to be really as there was no CAT in there to begin with)
Next on the shopping list - A SS Downpipe.
Anyone got one for sale ....?

Ro

Scoobysport http://bbs.scoobynet.co.uk/wink.gif

RoShamBo

I have the SS DP and backbox, and i also had the STi5 centre section with no CAT to start with. The Magnex centre has made a huge difference, ask Kris who absolutely rinsed my car today when he drove it!!! http://bbs.scoobynet.co.uk/smile.gif

rinsed ?

he washed it for you ?

cool...

J.

...wanna go for a drive in mine Kris - it needs a good wash .... !

Ro.

[This message has been edited by RoShamBo (edited 31-01-2000).]

You northern paffs...i dunno....get wid' tha' program geezer or else http://bbs.scoobynet.co.uk/smile.gif

Tell 'em, Sunil, somebody has to http://bbs.scoobynet.co.uk/wink.gif

"The main problem wot people 'av wiv the aRS Coswurf is dat she is so MING-ing..."

Sorry, seem to have gone OT(T) there

Booyakkashah!

-= mikey B =-

Innit!....pooooonnnnnnnnaaaaaaaaannnnnnnnnnniiiiii iiii