dhorwich

Would it be feasable to buy a standard downpipe and gut the cat out of it, done this on a previous car and it worked pretty well...(celica GT-Four)..

Would it work on a scoob, i.e if i buy an old downpipe and remove the cat out of it, would i see the same benefits of a de-cat downpipe.....???

Any thoughts.

Dan

hades

The standard downpipe doesn't have an opening behind the wastegate. Nearly all aftermarket downpipes either have bellmouth, twin dump or variations on these themes. Therefore, allows much better flow out of the turbo than a gutted OEM would have. The only two exceptions to this I can think of are the HKS downpipe and the Power Engineering T65 (although the "proper" Power Engineering exhaust - the T75 - does have a twin dump)

Having said that, I'd think it will make some improvement gutting it, just not nearly as much as buying a decent performance downpipe.

dhorwich

Im just thinking along the lines of £20 for a standard second hand downpipe which i can gut... and £120 + for a de-cat...

Just wondering what the large diameter left in the downpipe will do to performance after gutting it.... would it cause flowing problems.... anything is better than the standard cat/downpipe and if HKS do one then it cant be all bad...

Dan

hades

For £20, "suck it and see"! You might still get better spool up and maybe 5bhp, which is very good £/bhp ratio.

FWIW, gutting a cat on an old Cavalier GSi (not mine) many years back made a big improvement. Although it got better still with a proper cat replcament pipe, I'd say a gutted cat gave about 2/3rds the gains on that car - I assume most of the other 1/3 was lost in turbulence in the big empty chamber.

David_Wallis

Dan...

Come over one weekend and Ill do it for you if you get some tubing..

I bought a downpipe to do the same... then went 3" instead..

David

dhorwich

david,

I might just take you up on that...!!! still getting my f***ing car fixed, been messed about with parts e.t.c but at least its started now..!!

Do you mean, literally cut the cat out and weld a pipe in its place..??? hadnt thought of that..!!

What you been upto on the DIY front of late... Got a bit worried the other day as i saw you posted on a thread in for sale forum advertising an escort cossie...!! looked nice though..!!

Dan

[Edited by dhorwich - 12/1/2002 7:19:03 PM]

M0NEY

I was looking in to getting a downpipe and was going for the HKS but someone recommended to go for scoobysport instead as it would be better. Not sure but before you buy the HKS, worth looking into

dhorwich

money,

The HKS one mr wallis bought was modified by himself.... so it was open neck..!!!

Dan

green_dragon

I've done exactly that - TIG'd a piece of stainless tube * preformed bend into where the cat was. I made up a jig to hold the downpipe and tack welded it on so that when I cut the cat out it didn't move, then just welded the tube and bend in.
Watch out if you decide to cut the cat out, there's a few health risks from both the substrate and washcoat. Wear a mask and you should be OK.
The improvement in spool-up, noise and performance were well worth the effort, I paid £30 for my downpipe - looks like I was ripped off!