Secondary Cat

[sw20kosh]

Quick question: Does removing the second cat affect the performance of the engine? Does it throw a Check Engine Light?

How about smell? fuel economy?

Thanks!

[shu5892001]

Yes, it increase hp as you open up the exhaust more
No, 2ndary cat is after the sensor which will not throw a CEL
Negligible, as you still have primary cat
Negligible, might even increase mpg

[Craig]

Originally Posted by shu5892001

Yes, it increase hp as you open up the exhaust more
No, 2ndary cat is after the sensor which will not throw a CEL
Negligible, as you still have primary cat
Negligible, might even increase mpg

All of these true, just installed my Motiv test pipe (no cat/no resonator) with my stock catback (soon to be replaced).

No CEL

No more smell, slight increase in exhaust tone -will be much louder with catback-

My MPG has gone up, not sure how reliable the fuel counter is but it's about .5-1 mpg better than prior to the change.

As for increase in power, I would say the delivery of power is smoother, TQ dip isn't as bad, and top end is slightly different. I actually see most of the improvement below the 5k mark (where most of my driving is anyway) and it seems to pickup a bit quicker. Not a night and day difference, but worth the ~200 it cost me.

There's more exhaust smoke for sure on a cold startup, but I could care less about that.