I put my stillen true dual on with the berk HFC and I noticed the exhaust will hiss contantly while under load above 3k rpm. Now I slapped some BERK test pipes on and now it hisses even louder above 2.5k rmp up to 5k-6k rpm. I know that Testpipes hiss when you rev it but my exhaust hisses while driving under load constantly. I had the bolts checked and the exhaust shop is saying there are no leaks. Anyone know of a fix or know why this is happening? Ive had testpipes on the greddy Evo2 and the Nismo and there was no hiss under load

 

hmm.. Ive never heard of this before, maybe you got a cat stuck in the resonator?

 

If it's hissing there has to be a leak somewhere.

The Stillen exhausts don't normally hiss.

 

it sounds like a bunch of birds chirping/whistle sound under load and just progressively gets louder. Im gonna try change out the gaskets and if that doesnt work im gonna slap on some resonators.......

 

Resonators won't help if its a leak.

There are parts of the exhaust that are slip fit and clamped.
Check the slip fit areas.

 

Sounds like you have an exhaust leak. If you can get the car on a lift while its on feel around the flanges for air. Cover your mouth with something and dont put your hand on the hot pipe...just feel around it. If its leaking order new gaskets and check if the ring the gasket goes around is even.

 

2 of our guys down here with the stillen have the hissing sound also

 

There is a snake in your exhaust watch out! No really I would check for any exhaust leaks, after driving on a new exhaust for a while its always a good idea to go back and re torque the bolts to spec. My Fuji had a similar problem when I first installed it, added some liquid gasket and re torqued. Hissing disappeared.

 

did ya do a before/after dyno btw? just read about stillen true duals making big power gains on revup motors. was intriqued.

 

no i havent dynoed it. I can tell you the nismo i had before mad no extra power on the dyno. Im gonna try taking apart the exhaust and replacing gaskets/bolts. thanks for the input guys

 

If there's really no leak, it could be from flex-pipe. Exhaust systems with poorly-designed flex-pipe section will hiss like **** when mated with TP. My old Greddy Evo2 with its crappy *** X-pipe hissed even with HFCs.

 

The Stillen doesn't have flex lines.

 

Yea lol I completely forgot that Stillen is TD exhaust. Oops