Author Topic: Any difference on dump valves?  (Read 2496 times)

Ruivar

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Any difference on dump valves?
« on: 12:42, Thu 27 January 2011 »
Hi,

just a quick question as I was browsing on the Forge site.

Are there any difference on their different dump valves? They have got many different valves to very different prices. Is a more expensive dump valve any better?

Cheers.
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Boostjunkies

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Re: Any difference on dump valves?
« Reply #1 on: 16:42, Sat 05 February 2011 »
Basically they are broken down into 4 types,

Diaphragm, this has a nomex or rubber (depending on quality) diaphragm in it, Mostly used on cars without an AFM or metering unit, Ie renault 5, Sierra Cosworth, but they can be unreliable, splitting and are used more where the inlet temps are high ie pre intercooler.

single piston, this has a single piston mostly used for cars without an AFM or metering unit and the inlet temps are low (post intercooler) and are more generally more reliable than the Diaphragm type.

Twin Piston, this has a secondary piston that closes behind the first to stop stalling and running problems on AFM and cars with a metering unit ie RS turbo MFI, (basically the engine runs briefly rich with each operation of the std single piston causing running hesitation or stalling)

and Then there are variants that have the charge released back into the inlet just before the inlet
These are re-circulating Dump valves. (diverter valves)

There are also some that allow a part of the charge to escape and the rest is re-circulated usually with an adjustment screw to change the spring tension and the amount that goes back in,
These are mainly used on cars that have MAF's and AFM's, and again have stalling problems with Atmospheric dump valves in general.

finally there are dump valves for the specifically VAG cars and other Diesels that have an electronic control on the top, too stop Stalling and poor running issues as the Turbo's either are variable vain and ecu controlled or have a sensor for boost pressure in the turbo housing.

That's my understanding of them anyhoo.

Ruivar

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Re: Any difference on dump valves?
« Reply #2 on: 20:36, Sun 06 February 2011 »
Thanks mate. A rather technical description there. It seems you know what you are talking about!
As I understand, it is the single piston valves that suit the GT turbo the best then?

Thanks.
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Boostjunkies

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Re: Any difference on dump valves?
« Reply #3 on: 23:25, Sun 06 February 2011 »
Yes mate it will be fine,
you could use any of them on the 5's but the twin may not dump very much,
the single piston will take be more reliable in the long run

Ruivar

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Re: Any difference on dump valves?
« Reply #4 on: 07:41, Mon 07 February 2011 »
Thanks a lot, mate.
I am not in need of a new one at the moment, but mine is getting older so I want to be prepared when it breaks.
Although I am not sure if I want to use a dump valve again. I have never tried compressor surge, so that might be an option.

Cheers mate!! 8)
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Boostjunkies

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Re: Any difference on dump valves?
« Reply #5 on: 11:50, Tue 08 February 2011 »
I ran all last year with out a dump valve, but I have a a Garrett steel core and 360 deg bearing on the skyline,  it is slightly more laggy but the noise is funny,
I have returned to a twin piston again though as we're using it more on track this year and want to keep the turbo healthy at the higher boost levels :)

Ruivar

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Re: Any difference on dump valves?
« Reply #6 on: 16:54, Tue 08 February 2011 »
Hi,

what kind of pressure are you running on the turbo without a dump valve? I take it the turbo will not last as long without a dump valve, if the pressure is too high? I run a hybrid t2/t25, by the way...
What are your experiences with compressor surge vs. dump valves at different boost pressures?

Cheers, mate! 8)
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Boostjunkies

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Re: Any difference on dump valves?
« Reply #7 on: 12:33, Thu 10 February 2011 »
well on the fiesta XR2t running the T3 hybrid I was running 28/30 psi
and the Skyline it's 1.2 bar about 16-17 psi both have been fine but both have been uprated,
You can get an adjustable dump valve so it flutters under a certain boost and dumps over that spring rate setting,
best of both worlds :)

As for the difference between running and not running one, it's slightly different on the way the turbo comes in and the delay of engine breaking, the dump valve the boost dumps  and is really sharp responsive when you accelerate and you get better engine braking,
without it's slightly smoother on and off boost and it's better if coming of and back on the accelerator quickly once on boost but running higher boost levels the engine takes slightly longer to  get rid of the boost, but it's only just noticeable.
The best thing to do is buy a dump valve blanking plug and experiment lol :)  I like both but
the dump valve wins really due to turbo longevity and It's a track and show car so has to make a noise lol
Matt

Ruivar

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Re: Any difference on dump valves?
« Reply #8 on: 15:19, Thu 10 February 2011 »
Hi Matt, thanks a lot for your answers. 30 psi is extreme :-) How much power does that turbo produce?

Quote from: "Boostjunkies"

You can get an adjustable dump valve so it flutters under a certain boost and dumps over that spring rate setting,
best of both worlds :)
I have never heard of a dump valve making both the flutter and the dump noise. Can you tell me where to find such a valve? It sounds perfect :D
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Boostjunkies

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Re: Any difference on dump valves?
« Reply #9 on: 11:37, Fri 11 February 2011 »
It's basically a dump valve that has spring adjustment mate, it allows you to adjust when it dumps so bellow that levels it flutters and when the spring rate is reached it dumps, simples,
same ones used for cars with idle problems with Atmospheric dump valves, has an adjustment screw on the top :)

Turbosmart have an adjustable dump valve and they are usually very loud lol

Boostjunkies

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Re: Any difference on dump valves?
« Reply #10 on: 11:40, Fri 11 February 2011 »
the Stage 3 hybrid I had on the fiesta later went on the 2ltr zetec turbo engine I built and that made 265 bhp at 14 psi, when it ran the 28-30 psi it was on the 1600 cvh turbo it was around the 200 bhp mark, they work hard on the smaller engines,
The skyline makes 420 bhp at 16 psi but it is 24v and has 6 cylinders lol

Ruivar

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Re: Any difference on dump valves?
« Reply #11 on: 15:41, Fri 11 February 2011 »
Thanks a lot, mate. I will take a look at those valves.

I appreciate your help. I am definately feeling smarter now :wink:

Cheers mate!
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