Quote:
Originally Posted by ravenblackfrs
Should I go ahead and do header back with cat? I know you said do without the cat but I'm not going to be able to get away with that living in Atlanta. Would that large of an exhaust cause me to lose back pressure on the stock engine?
Sorry, I'm a noob at some of this stuff.
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Yes, you will likely lose some torque with an exhaust that large. Back when I had the Nismo 370Z, I had the Greddy Turbo Ti-C exhaust which was 2.75" and I lost about 3wtq on a dyno. But I gained about 7-8whp. If you do go the exhaust route, if you are planning on staying naturally aspirated, then go with 2.5".
I'm not sure of the high flow cat options for the FR-S/BRZ as I am running straight turbo all the way out of the catback without any cats inbetween. But if you can go with a headerback exhaust with high flow cat, that would be your best bet. You would still most likely pass emissions. Sometimes the CEL could possibly go off, but they usually go away. It's just because most highflow cats are right at the edge of throwing off your oxygen sensor's accepted values. Depending on when you bought the car, if you bought it new, then you have exactly 2 years after purchase until you have to get emissions testing done.
If you got the headerback (header,highflowcat,catback) all in 2.5", I would expect ~25whp without a tune. Possibly ~40whp with tune. It would be loud as shit though. Unless you got a catback with a damn good muffler.
Good luck