I have recently de catted my 98 sti and since doing this i get a horrible tinnie flapping fluttering sound when i put the foot down. I thought it was the dump valve so removed it and its still there. I have since been told its the waste gate on the turbo. Is this correct?? I think it sound rough or is this normal? Scoobysport d/p, magnex resonated centre. and scoobysport b/b. I also thought it would of been alot louder being de catted but not a great deal better.

You can definately here the wastegate open and close more clearly, though you will also here the spool up of the turbo.

If it is a whiny sound it may be that the downpipe studs need to be tightened as the seal is not a snug fit, therefore venting air.

MCGARY

If the noise occurs as boost starts to build then it is indeed the wastegate. The wastegate is driven by a solenoid which fires pulses of gas. By pulsing, it allows a smoother, more accurate control and prevents any jerky action which would cause boost fluctuations.

As the wastegate starts to open, the valve flap initially vibrates against casing and this can be heard. It was doing the same thing with the standard downpipe, but the extra sound deadening on this stopped you hearing it. Every after market downpipe does this.

If there was a leak from the downpipe, this would sound like a nasal roar and would continue up the rev range from where boost was achieved.

Since October 2002, all Scoobysport/Janspeed exhaust section flanges have been surface ground at the end of assembly. We have never known one to leak when fitted with a new gasket.

edited fur por spullin ;)

[Edited by Pete Croney - 5/14/2003 8:54:59 AM]

It would be louder if you had a Non-resonated centre pipe.
You have the resonated one which keeps the noise down, good for some people or bad for others!

Thank you for the replys. At least i now know that this is normaal. Cheers Gary

Mine does it too........when I first noticed it, I thought it was the dreaded "Knock":(:
Alcazar