Originally Posted by Farthestnorth
With 600 plus horsepower why would you even want tne cats in there? No need for them whatsoever, straight pipe to an X or H pipe would be best!
Anything we build, to be used on the street requires catalytic converters. No question that as the power level increases that they can become less efficient as as well as a restriction.
We have built numerous Camaros with well over 600rwhp and cats, with NO issues.
Both #001 manual and #002 automatic are utilizing the full stock 2.5" exhaust.
While a 3" system with X or H pipes could see an increase in power, it would also reduce the clearance by the coolant lines as well as around the rear differential. ( IMO, re-routing the coolant lines would be recommended with a 3" exhaust.)
We programmed the diverters in the mufflers to open and close electronically without vacuum inputs. We are very satisfied with the sound quality both in and out of the cabin, with the stock exhaust system on these builds.