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Hi all

New to the forum. Owned a 2004 BMW M3 SMG prior to my RS4.

Are catback systems on the RS4 worth it ? How about just removing the cats and keeping the stock system.

The car will have a remap if i go either way. Just wondering if the gain vs $$$ is worth it.

Thanks

If you do go cat back, then go non resonated to get the best sound gains. As you will see from Brooner's thread 'MRC Magic' a map will get you gains and a cat back and map will improve on that.

The real gains are to be had are remapping a NA car with cats removed or sports cats however given VCA on a VOSA guidelines on the implications of doing this for UK car owners now, you potentially run the risk of either having to change the system back to original or getting a maximum £5k per cat fine if you are discovered (4 cats with an RS4).

As to costs, for sound alone and better pick up + mpg a cat back is worth it IMO. Dependent on who you buy from prices range from £800 - 1800 dependent on manufacturer and whether non resonated / resonated and whether you have a valved or non valved system.

P_G wrote:If you do go cat back, then go non resonated to get the best sound gains. As you will see from Brooner's thread 'MRC Magic' a map will get you gains and a cat back and map will improve on that.

The real gains are to be had are remapping a NA car with cats removed or sports cats however given VCA on a VOSA guidelines on the implications of doing this for UK car owners now, you potentially run the risk of either having to change the system back to original or getting a maximum £5k per cat fine if you are discovered (4 cats with an RS4).

As to costs, for sound alone and better pick up + mpg a cat back is worth it IMO. Dependent on who you buy from prices range from £800 - 1800 dependent on manufacturer and whether non resonated / resonated and whether you have a valved or non valved system.

Thanks for the reply. Would you suggest keeping the OEM exhaust and removing the cats. We don't have the "law" problem in South Africa

one word... YES!

P_G wrote:The real gains are to be had are remapping a NA car with cats removed or sports cats however given VCA on a VOSA guidelines on the implications of doing this for UK car owners now, you potentially run the risk of either having to change the system back to original or getting a maximum £5k per cat fine if you are discovered (4 cats with an RS4).

Do you know if this is the same for bikes as was thinking of de-catting my bike ? I think (hope) emissions laws are a bit different as my (E-Marked) Termignoni exhaust kit came with a blanking plug for the O2 sensor to take it out of closed loop running & a new ECU chip that doesn't object to losing feedback from the O2 sensor. The baffles had little (tiny) tackwelds to "prevent" someone from removing them so the Italian spirit of following laws is still alive & well !

I run a trial where I had the OEM exhaust linked up with 200cell Millteks and MRC remap..worked and sounded fine. cant see that being a problem.

You may get EML flashing due to the warm up cats not being in place.

MB2 wrote:

P_G wrote:The real gains are to be had are remapping a NA car with cats removed or sports cats however given VCA on a VOSA guidelines on the implications of doing this for UK car owners now, you potentially run the risk of either having to change the system back to original or getting a maximum £5k per cat fine if you are discovered (4 cats with an RS4).

Do you know if this is the same for bikes as was thinking of de-catting my bike ? I think (hope) emissions laws are a bit different as my (E-Marked) Termignoni exhaust kit came with a blanking plug for the O2 sensor to take it out of closed loop running & a new ECU chip that doesn't object to losing feedback from the O2 sensor. The baffles had little (tiny) tackwelds to "prevent" someone from removing them so the Italian spirit of following laws is still alive & well !

http://www.mira.co.uk/News/documents/re ... ations.pdf

sonny wrote:I run a trial where I had the OEM exhaust linked up with 200cell Millteks and MRC remap..worked and sounded fine. cant see that being a problem.

You may get EML flashing due to the warm up cats not being in place.

Thanks. Was there any power gains/sound change?

Sound change yes, Power gains was not mesured.

sonny wrote:Sound change yes, Power gains was not mesured.

Seat of your pants feeling ?

Veyron fast trouser moment.....

Thanks for that - it seems at the moment bikes aren't emissions tested but to meet Euro 3 a cat is compulsory so for some reason they are working on the assumption that bikers don't remove the cat (that group of road users so well known for never modifying their exhausts...) so it would seem correct answer is "no" but in practice "no problem" !