Originally Posted by knottz
The cats are I believe froma company called cat co - all stainless to go with the exhaust. Fin will know more but in a nut shell it goes
manifolds which go from four each side into 2 each side,
Into a collector made by fin
Through each of the cats / again 1 per side
Then an X-pipe
Then custom made resonators ( which aint much bigger than the pipes)
and then out to the tail pipes
Each tail pipe has an inner perforated tube just to trim the noise down a little more, but cruisin thru town at 30 or 40 and lifting off brings a nice number of pops as the engine spinns down a little, its the kinda sound that by lookin at your car in the pics I'd expect to hear from it
The American CatCo Cats are designed to work with GM (and other V8 applications...ie the SBC 5.7... they quote a 25% increase in flow over stock.... And they are fully emissions legal and out flow the original BMW efforts (they are total over kill...as is the rest of the bmw system....Remover the Y resonator
Yes I buy my Cats from the USA :-)
The first pair of silencers in the system are 2.5" to 4" to 3" then a length of tube then down to 2.5" again. Inside is 2.5" perforated tube.
The Expansion part of the tube has no wodding/sound media behind it. The 3" od section has a single layer of our sound media. please see thelink for details
Then into the main silencers 2.5" Perforated tube with a 4" od
The end tips are 2" perf by 10"(If i remember right) inside the 2.5" tube again with one layer of sound media.
Hope this helps,