Hi I have a 99 uk impreza turbo with a few mods giving me around about 260bhp. I was given a forge dump valve from the previous owner which I fitted the same night I got home - had it on the car for a few months but got fed up with the noise and took it off a few weeks ago. The sound I would really like is the sound cossies make like a wastegate chatter type sound, is this possible on an impreza if so how?? I've heard these hks ssqv bov things make a bit of noise but have never actually heard one before.
Any help is appreciated. I realise I will probably start a mega debate on the pros and cons of dump valves or chav valves just looking for some help.
Thanks

 

Without getting into a debate about dump valves, to answer your question wastegates don't 'chatter'. I don't know where that phrase ever came from. The sound you're talking about is compressor stall caused by a rapid throttle off trapping boost between the turbo and throttle. Without a dump valve, this boost simply exerts pressure back onto the compressor and slows it down. With an open induction kit you can sometimes hear this twittering sound as the air is 'chopped up' as it is forced back into the turbo. With a standard Scooby dump valve this trapped charge is diverted back into the inlet again, but in the case of an atmospheric dump valve, it's simply vented to atmosphere. On light throttle offs you'll still be able to get compressor stall because the dump valve won't open fully. On a 'full volume dump' you often won't hear the compressor stall at all, because the dump valve is doing it's job properly and allowing the compressor to keep spinning.

 

trolling rubbish

 

removed as part of above

 

thanks nick read for your help.

 

No problem. I'll always tell it straight! And yes the twitter of compressor stall is a bloody excellent noise, although I'm happy with my discreet factory recirculating dump valve. But if you like a bit of a twitter that's my advice, get an open induction kit and a VTA dump valve. Somewhere along the line you'll get the twitter you want. As I said, on my old motor it was on gentle throttle offs where the dump valve wasn't able to dump a full charge and compressor stall still happened. In fact funnily enough when you're really going for it (e.g. quarter miling) and you've got a decent high-flowing VTA dump valve, if you're banging through the gears you'll hardly hear it either, just a very loud chirp for a fraction of a second.

 

Nick,

I've got a Blitz blow off valve and blitz open induction kit. I have the sound you re talking about! It really does sound excellent, really audiable inside and outside the car!

Nick.

 

Can you take a recording for me then please so I can hear it!

 

No worries greegs!

Suppose you just want me to do it with my mobile ant then txt you it?

Nick

 

Go for it nick! I've sent you a private message with my mobile number, cheers mate.
Gregor

 

Blanking plate between stock DV and TMIC will create the sound you are after - don't try it on a VF series turbo though (although one of my customers has been running a VF34 at 1.3 bar like this for around a year with no problems reported), their compressor blades are a bit weak.

Richard

 

buy a td05 and dont run a DV at all