Check this out, http://www.harmanmotive.com/catalog/...oducts_id=1473

These guys claim the BMW 335i can make another 30 hp and roughly 30 ft lbs more power without catalytic system on. I noticed on the dyno graph that it is running boost, I'm not at all familiar with 335i's but that is cheap power! makes you wonder why you guys are running Superchargers on those srt6's.

 

Wow, that's pretty impressive. I wonder if that set-up would make the ECU unhappy since it has O2 sensors on each side of the cats.

I don't even want to think about what the smog police would say!

 

02 simulator for the 02 sensors but if the car was boosted probably turbo'd that's why it made such an improvement. On an n/a car I would think we would just lost bottom end torque.

 

Yeah I believe your right, it's allowing the turbos to spin a little faster. I bet we would probably see a gain of 8-10 hp realistically.

 

I'd guess even less. You can take the cats off on an LS1 Fbody and pick up just 8-10 hp, or take them off a Viper GTS and pick up about 12-15 horsepower. Since the Crossfire is making much less horsepower than either of those, I'd wager 5-6 horsepower. A change in the outside temperature or humidity can produce similar kinds of changes on a dyno.

I'm no hardcore tree hugger, but removing cats just doesn't make sense to me. The extremely little upside isn't worth the impact. I've built a number of blown and nitrous cars, and managed to make them all run just fine with cats installed. I have kids you know :-)

Mike