Wastegate Noise-a lack off?

[Nick]

HI, I'm a new member although I've had my RS2 for some months

I've read a number of reviews that mention the car 'breathes noisely' on the shifts and test drove a car that chirped just like the rally quattros.
My car however remains virtually silent and although the performance seems fine I wonder if it should make this sound and if there is an underlying reason that needs to be looked at?

Nick

[s4woody]

is it a recirculating wastegate or one the vents to atmosphere. ? recirc are quiet atmos vented aint..i believe

[venetors2]

the original plastic pop off valve could be silent or not it depends........mine for example is noisy (soundy)
i would not going into an open air one though because the recirculation helps (little) the turbo on keeping spinning

Ciao!

[Nick]

Thanks for the replies. I'm currently trying to read up about turbo systems but as I understand it the car doesn't have a dump valve as such but uses the wastgate to lose excess boost.....and maybe this oscillates during operation?
I hope I'm not giving the idea that I want the loud woosh that so many 'improved?' cosworths etc sport but I'm a curious type and would like to understand why my car is relatively quiet. Looking under the bonnet there appears to be a fair old run of tubes but with no manual to explain things I guess I'll need to draw up my own diagram and do a bit more reading.

[alastairg]

Nick. You can get some Xs boost noise with sudden lift off WOT however any other noise suggest you get it replaced with S3 DV.

[AAH!]

Nick. You can get some Xs boost noise with sudden lift off WOT however any other noise suggest you get it replaced with S3 DV.

Or if you want to spend a bit more for more or less the same thing look at this:

http://www.forgemotorsport.co.uk/conten ... =FMCL007PA

and if you want to hear it a bit more get a K&N replacement air filter.

If you want to hear even more from your DV along with other wooshy go faster sounds, loose the OEM airbox and get a cone filter.

I did

Angus

[AndrewD]

Think there's a bit of confusion here between wastegates and 'dump' valves ...

The wastegate is the big thing sat on top of the turbo area. It prevents the turbo from spinning too fast and/or producing too much boost by gradually allowing some of exhaust gases to bypass the turbo as boost builds.

The dump valve is the device that prevents too much positive pressure building up in the intake system inbetween the turbo and throttle valve (i.e. in the intercooler, etc) when the throttle is suddenly closed. The recirculating vale in standard cars affectively allows the system to depressurise and dumps the air back into the intake system downstream of the air-flow sensor and upstream of the turbo. This reduces stress on the turbo and intake pipework.

Some people fit dump-to-atmosphere valves which give the classic 'psssht' on gear changes as the air is blown out under pressure rather than back into the intake system. The disadvantage of this is that the engine management can get confused as metered air is being 'lost' causing the car to run temporarily rich. This can do bad things to catalytic converters!

The 'chirp' of the rally cars is most probably due to the fact that they don't run any dump valve at all. This means air is forced back over the spinning turbo when the throttle is closed causing a chirp as the pressurised air hits the blades. The advantage of this is that the intake system remains pressurised between gear changes which in turn means that full boost is regained quicker. Disadvantage is that there is a lot more stress on the turbo and intake pipework.

[Nick]

Thanks for your comments Andrew. Your explanation ties in with what I was beginning to understand. I think that the standard Bosch valve can have a tendancy to oscillate and this was probably the noise that I've heard. I'm sure my car has had this replaced...maybe to a different type which is silent. I've been reading Corky Bells book about turbocharging but so far as I can see theres no mention of dump valves just a reference to a 'emergency' boost limiter that vents to air. His book is not that old (95') so this seems strange but I guess things have moved on rapidly since he put pen to paper.
I have an article that refers to the S1 rally car having a recirculating air system? and I'm sure another somewhere that mentions injecting /burning fuel after the turbo to keep it spinning...or maybe I dreamt that bit??
Still I'm happy to keep my car as is and enjoy it's amazing performance with daily driver reliability..great car!

Rgds
Nick

[alastairg]

DV to atmosphere rather than recirculating (as on RS2)='emergency' boost limiter. Its simply a valve that allows unneeded boost to be 'removed'.