D Spin

downpipe and stock exhaust?

I currently have a Magnaflow high flow cat and there is a leak in the flange that attaches to the turbo...I have to remove the cat to have it re-welded and would like put in a larger diameter down pipe while I have everything apart.

A few questions though,

-I've seen 2.5" diameter and 3" diameter DP's any suggestions on which diameter to go with?

-I would be attaching it to my stock exhaust (I just don't have the $$ right now to do a whole aftermarket exhaust) anyone see problems with using a reducer to attach the DP to the stock exhaust or does anyone know of a company that makes a large diameter DP that comes with necessary parts to tie into the stock exhaust?

-I am running an APR chip(KO3 turbo) and this is the third time that I have blown a Cat flange, my thinking is too much back pressure from the exhaust and maybe a larger DP would help this?? Or is it a waste of money to put in a new DP without a full exhaust?

I'd appreciate any input...
Thanks!

dorsal900

posters on saabnet (my other car is a SAAB 9000) have done the larger downpipe with stock exhaust on their cars; they report that the larger downpipe gives the most bang for the buck, faster spoolup, etc., much more effect than a larger exhaust with a stock downpipe.

Allroady DungBeetle

You may have broken motor mounts if you keep blowing the flanges - 2.5 DP is about all you'll need or see any gains from with a K03. Even then it's minimal.

If you need to replace it anyway then go ahead but the gains will be slight. Maybe a little seat of the pants quicker spool up on the turbo.

The back pressure is NOT blowing the flange. You have too much movement somewhere - either in the motor mounts/trans mounts or the exhaust itself is not supported correctly.

Waste of money.... meh, maybe but not certainly. Depends on your driving style and future thoughts on upgrades.

For the $$ it's hard to beat a full cat back Borla exhaust and seeing as they have a "lifetime" warranty it's worth thinking about since if nothing else the flex joints do tend to crap out pretty often on these cars.

Allroady DungBeetle

This is generally true of all turbo/SC'ed cars & trucks.