[Bsm550]

I recently installed catless downpipes and the sound is fantastic esp with the high flow middle section but my only issue is the smell is crazy i had catless dp on different cars before but this car stinks would the catted downpipes make a difference

[mike@x-ph.com]

High flow catted will drastically reduce the catless smell

[darkrom]

It'll reduce it but not eliminate it, and if you plan on running a burble tune forget it you will eventually have to replace the high flow cat because it will ruin those just like the OEM ones. Plus you will still have an emissions light with basically all of the high flow cats besides the $1000+ ones, which have the same cell count as stock to not throw a CEL.

[WretchedRefuse]

Originally Posted by darkrom

It'll reduce it but not eliminate it, and if you plan on running a burble tune forget it you will eventually have to replace the high flow cat because it will ruin those just like the OEM ones. Plus you will still have an emissions light with basically all of the high flow cats besides the $1000+ ones, which have the same cell count as stock to not throw a CEL.

It says here that the Active Autowerke catted DP has a cell count of 400, and I remember reading somewhere that OEM is about 600 but I can't find a reference for that. Most "high flow" catted DP's have a cell count in the 200-300 range. I assume that fewer cells means larger cells, implying less backpressure if all else is equal.

[yupetc]

Active Autowerke uses the GESI cats which are rated for 500-850whp and still get you emission compliance. Those are 400 cell count and will not trip O2 circuit faults. You may still not pass the strictest smog checks, though. Just keep that in mind.

I make my own GESI catted DP and run them on my N55 and B58, both work very well and have no smells once the engine is up to operating temperature.

Below is the link to what I use:
https://www.cspracing.com/g-sport-85...50hp/gs-85200/