Re:strange hissing sound
 

go on Kazaa. search video files for "1000hp supra"
It's a video of a 1000hp supra on a dyno with a camera pointing at the engine. Listen to the sound, is that the sound you are hearing?

Re:strange hissing sound
 

its your air intake...when i had my prelude i had a stock intake and then i changed it out with a 4inch intake pipe with k&n air filter and it made a " tssst " sound all the time but got hella loud at 7000rpms....it could be heard a lil bit at idle but only cause the damn thing was so ------ huge.lol....

Re:strange hissing sound
 

hehe turbo Si's rock.

go take a plastic bag and stick it out your window and go about 40.

is that the sound your hearing. if so its normal. its just the way the car sounds when vtec activates. makes the turbo spool harder and thus the sucking of the intake makes more noise...

its one pimp sound.

Re:strange hissing sound
 

thanks guys for all your answers, i think it may be my manifold leaking air at high rpms and i think i need to tighten it more, it only make it when there is someone in the car with me though, oh well...

Re:strange hissing sound
 

i have to agree its probly the intake. When i made my intake to a 3in dia intake tubeing and slaped a performance filter on it ,it made a loud sucking noise and when i hit the gas it makes a sweet sound like a turbo spolling up real fast. But I still have that hissing sound i love it scares ricers ;D

Re:strange hissing sound
 

my car makes that sound to , ive come to the assumption that its a combo of the turbo spooling and a high velocity of air moving thru the system. wicked!