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986Jim · 05-10-2006, 05:56 PM

Second cats are not to decrease the noise level, they are to meet a specific emissions quota. You can eliminate them and still pass emissions and pick up some extra hp too.

Many new cars now have a precat thats right off the exhaust manifold and a secondary (normal) cat thats under the car part way like we are used it. Having the cat right off the manifold allows it to heat up faster and start to clean up the emissions more quickly from a cold start. It's all part of reaching ULEV standards. Not sure if the box is ULEV but with 2 cats I'll bet it close.

The current generation WRX has 222hp and meats ULEV with a precat and main cat.

05-10-2006, 05:56 PM	#2
986Jim Registered User Join Date: Feb 2006 Location: Toronto Ontario Posts: 291	Second cats are not to decrease the noise level, they are to meet a specific emissions quota. You can eliminate them and still pass emissions and pick up some extra hp too. Many new cars now have a precat thats right off the exhaust manifold and a secondary (normal) cat thats under the car part way like we are used it. Having the cat right off the manifold allows it to heat up faster and start to clean up the emissions more quickly from a cold start. It's all part of reaching ULEV standards. Not sure if the box is ULEV but with 2 cats I'll bet it close. The current generation WRX has 222hp and meats ULEV with a precat and main cat.