de-catting

[haggishead]

forgive me if this is an old one, but i've searched and can't see an answer...

If i want to decat my S3 (1990) is it just a case of getting bypass pipes that fit straight in, or do I need new manifolds / downpipes etc?

MOT soon...

[thegamekeeper]

£45 each plus vat in Stainless. bolt straight in as replacements. 01928 719267

[tvrmark]

The ECU will also need remapping

Mark

[beeka]

tvrmark said: The ECU will also need remapping

Mark

As I understand it, the sensors for the ECU are before the Cat, so there is no effect on the ECU when you remove them (the Cats). Certainly hasn't made any difference to the performance of mine, and I haven't touched the ECU. Any thoughts?

[GreenV8S]

Yes that's right. It's possible that by removing the cats you change the engine tune to the extent that it needs a remap, but I doubt you will find that big a difference. The only case where you absolutely have to remap the ECU is where you replace the cat exhaust with a precat one which has no mounting for lambda sensors - in that case you have to remap the ECU to run open loop.

[haggishead]

Thanks guys!

[tvrmark]

The remapping is because you've reduced the exhaust backpressure, when I removed the cat's the engine RPM went up by about 300 - 400.

Mark

[s27]

Did not encounter problems when I removed cats, and was told no work was needed on ecu.

SP