Dump Valve

[Green T5R]

Ok as many of you already know I have a Hybrid Turbo fitted to my car which does not have a dump valve fitted to it.

Does anyone think it would help by fitting one?

If I did fit one how easy would it be to remove if no improvement was found.

Regards

Iain

[Mrsmopp]

Have you not asked Turbo Technics this question?

x

[Green T5R]

Turbo Technics felt that the turbo did not require a dump valve but do say one can be fitted if a customer wishs.

I was just wondering if anyone here new of a reason to fit one other than for the silly noise they make......lol

[madness]

i think it definately needs one. turbo technics do not like dump valves so their answer is bias.

every car has one whether atmospheric or closed loop from the factory apart from cars delevoped before they were widely used that is........

more than anything they protect the life of the turbo

[Wobbly Dave]

Volvo (mitsi-based) turbos are fitted with a recirc valve. The whole point of the RV and the atmospheric dump valve as I understand is to prevent compressor stall during gear changes.
Personally I still think that there should be one.

[Green T5R]

Just got off the phone to TT.....Seems because I have a larger turbine the back pressure is not enough to stall the turbine, and because it is over engineered the back pressure will not damage the turbo.

Thanks for your answers all.

regards

Iain

[lance]

Dont take this the wrong way Iain, but I reckon you need to do a point 0 service and check for airleaks and get a compression test, Having read your posts here and on the voc forum it seems to me that you are down on BHP even taking into concideration transmission losses and all!
Just think it would be wise to do this while you are or if you are fitting a dump valve shortly.

[p fandango]

if it recircs the air back into the system so air isn't lost like an atmospheric DV, then how come i (& people with panel filters) can hear the recirc valve better, surley this indicators the air its getting to the atmosphere thru the air box?

[Green T5R]

might be me going mad....whats a point 0 service?

[Mrsmopp]

Stage 0 tune up - do a seach and it'll all become clear

x

[madness]

another question dave on recirc valves - Why recirc hot hot from the turbo twice when it is cold air we actually want????

[Green T5R]

good point....

guess thats one problem i don't have...lol

[Wobbly Dave]

I am not sure - I think there is a slight trade off between that and venting metered air into the bonnet space.

[Green T5R]

Just had an email for Turbo Technics with ref to fitting a dump valve and what cause the chattering noise,



Regarding your question about wastegate chatter. It is actually flow reversal. As the throttle is snapped shut, the compressed air has nowhere to go but back against the compressor wheel which produces an audible chatter. To put it simply, it is aerodynamic sound. If you have a small handheld fan (the sort you get sold when you go on holiday!!), try blowing on the blades as it's spinning, it produces the same sound.

On vehicles with dump valves fitted as standard, this won't be heard as the pressure is released. Now this brings us onto the age old question "should I have a dump valve or not?".

Volvos have dump valves built into the compressor housings, but this isn't for any performance gain, it is simply to stop surge problems with such an old fashioned compressor wheel design. Dump valves do not offer any performance gain, and are not needed unless you are using turbochargers larger than T4 size, as they simply won't produce enough boost to shatter any of the compressor blades.

Contrary to popular belief, a dump valve doesn't actually keep the turbo spooled better between gears either. In theory it is a sound idea: release the charge air so as to keep the turbo "free-wheeling" and not backing up against the compressor and stalling it. However, releasing all the pressure is not the best thing as the turbo then has to work hard as you come on boost to re-fill all the intake pipe work and intercooler before getting to the engine.

Hope this has helped,

best Regards,

Dan

[madness]

i think to an extent it is up to people to make up their mind as it will never be proved either way without alot of hassle.

but as so many people have taken one route or the other one thing is obvious
BOTH METHODS WORK and there must be next to no difference or alot people would have poorly cars !!!!!!! and big difference would be seen in performance

[SaffronC70]

Ian, a dump valve would be nice, but after seeing your car go, I don't think there are any problems between gear changes at all !