Quote:
Originally Posted by KingLT1
Fwiw, I have had 3 different NPP exhaust setups on my car. Last year I went to Corsa Sport mufflers (warranty claim) without NPP because the valved exhausts are shit. They rattle and make a hissing noise when closed because they don't 100% seal. I don't miss NPP at all and couldn't be happier with the exhaust sound and level. The sound level with the Sport mufflers is a little louder than the NPP was closed and it's a nice linear increase in volume as RPM climbs.
If I was you, I would simply switch to quieter mufflers. Then have the exhaust v band clamped so you can easily drop the axle back at the track. Or have electronic cutouts welded in under the car. Good electronic cut outs seem to have a better valve and stronger motor to seal. The stock valve actuator and valve in the axle back mufflers are not very strong and an engine that flows a shit ton of air(boost) can push the valve open/closed on its own. This is just my experience with stock, Flowmaster, and Corsa NPP. I also heard a Borla NPP and it was the same. JM2C YMMV....
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I always thought the vehicle opened the valves themselves no matter what mode you were on depending on RPM? Even if you're running a shitload of boost haha