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Hello

I am considering removing the primary catalytic converters and have a few queries. I'm aware that this requires removing the engine to gain access. I've heard that MRC are expecting to have some catless downpipes available for sale soon.

1. Would this make an appreciable difference to the cars performance? The car has a tune (APR) and no other modifications.

2. Would it be worthwhile also replacing the secondary cats with high-flow cats at the same time or is that overkill?

3. Would it hurt to remove the primary catalytic converters but not retune the ECU? In Australia as far as I'm aware noone does custom tuning on Audis, so all tunes are "off the shelf". APR will add a "testpipes file" if I go ahead but all this does is prevents catalytic converter error codes being displayed, the same mapping is kept. Obviously, its always better to get the car tuned for any changes in hardware, but if you can't would it do any damage to de-cat and not retune?

Cheers,

Steve

Speak to perthRS6, he has a 2 maps on his RS6 and he is in OZ, removing the primary cat will need to be coded into the map to stop the EML coming on.

taking that out it would be worth while getting a stage 2 map.

Combination of removal of primary cats, installation of high flow secondary cats and custom-made 3'' exhaust in my case resulted in 50 BHP gain across the revs. The car felt considerably faster but also MUCH louder. I'd advise to test one before doing so in own car as it is pain in the ass to get back to stock.

Best - T

Trups wrote:Speak to perthRS6, he has a 2 maps on his RS6 and he is in OZ, removing the primary cat will need to be coded into the map to stop the EML coming on.

taking that out it would be worth while getting a stage 2 map.

Thanks Trups, I'll contact perthRS6. I can get the software upgrade to prevent the car throwing codes for $250.

I would ideally like to get a stage 2 map if I went ahead. C6NVS suggested getting a distance tune with Viper which sounds promising.

TBl wrote:Combination of removal of primary cats, installation of high flow secondary cats and custom-made 3'' exhaust in my case resulted in 50 BHP gain across the revs. The car felt considerably faster but also MUCH louder. I'd advise to test one before doing so in own car as it is pain in the ass to get back to stock.

Best - T

Thanks TBl, I wonder if most of the noise increase was from the catback exhaust? I guess removing the primary cat only will still increase noise. Thats a good increase you got, was that with a retune or just the exhaust system changes?

it was 50bhp across the band just due to exhaust system change except for the peak power (c. 6500rpm) where the difference was smaller (can't remember exactly now). After retune it was 50bhp on peak revs as well.