I am considering removing the catalytic section of my exhaust from my 92 LPT and replacing with a 900 non cat downpipe (with small silencer). I am told this will give a small MPG gain and around 10 HP more - is this realistic ?
02-09-03, 03:55 AM
If you want the best performance increase - fabricate a straight pipe all he way to the back box. The small silencer in the middle will still disturb the gasflow and I can atest to this having replaced a silencer with a straight pipe as well as a cat with a straight pipe. It will be noisier but if you use a genuine Saab back back it is a very nice sound indeed! I would increase the fueling via a fuel chip of RRFPR as you may find that off boost response suffers a bit.
thanks for the advice Johann - is it a straightforward matter to fabricate a straight length? Would I just cut out the silencer on the non cat downpipe(or CAT on existing system) and mate the join with a slightly wider diameter pipe? i don't having welding gear/angle grinders etc so am really looking for a simple solution (if one exists!). I may just leave the CAT on if the non-cat downpipe doesn't add much.
02-09-03, 04:54 AM
It is a simple job - you can buy straight exhaust sections from an exhaust stock supplier that come in internal and external measured diameters - this means you can just cut off the cat flanges and sleeve on a section with the same internal diameter as the outside diameter of the existing. I joined it up with 4 saw cuts at the ends and some large exhaust clamps. It's much cheaper to do it this way as non cat downpipes are very expensive. You can do it all with a hacksaw but it can be a bit of a struggle when you are under the car - an angle grinder makes it a much quicker job.
Thanks - I have got a spare system off the car which I will attempt this on!