Which way round is the right way round for dump valves

[LDoR]

I know that this kind of quetsion has been posed before, but i never feel as though i really got the answer i was after.


My question really is to do with the way the piston in the dump valve sits.

The way i currently have i mounted the side of the piston sits facing the pressurised turbo air coming from the turbo pipe. The only thing that causes the piston to move upwards is when you lift of the throttle, a vacume forms above the piston causing the air pressure in the intake to push the piston up hence releasing the presuirsed air show here

Now i would have though that turning the Dump valve around would make more sense as the pressurised turbo air help push the piston out of the way to let the pressure escape into the intake faster as shown below.

I would have thought that attaching the DV as shown in the 2nd diagram would make it act quicker and give a better throttle response.

Or am i totally wrong and would the pressure form the turbo just hold the valve open all the time?

(As a side not where does the vacume tube go to anyway?)

 

[Fl@pper]

i would have said that the piston is spring loaded and therefore will only move as governed by the draw on the vacuum pipe

but gotta be worth a try ?

 

[LDoR]

Ah yes i forgot to draw the spring in these diagram and also missspelt a few words but at least you understant what i'm getting at.

I spose you all realise which DV i'm talking about as well

 

[Shock_Xe]

from what forge says it works both ways but one is more audioable than the other

 

[LDoR]

My concern is that installing it one way will create wastegate chatter.

I can't remember where i heard this, if it was related to which way round you install the DV or if it was to do with atmos type DVs causing wastgate chatter.

Any expert opinions on this?

 

[El Dingo]

AFAIK the way you have it fitted now is correct.
That is, with the turbo pressure against the side of the piston, as this has little or no effect on the effectiveness of the spring load in the DV.

The spring pressure works against the actuator vacuum. A heavier spring will hold on for longer (more boost). So, I suppose if you have the turbo pressure working against the spring pressure, this will let the valve open sooner and thus reduce available boost - it might also cause chatter, as the pressure is variable, and can come in waves (caused by resonance).

Does this make sense? Or am I waffling?

 

[LDoR]

I see where your coming from. In theory if i put it the 'wrong way round' with a high boost setting then the piston could be forced open slightly while i am on boost. However when i lift of the piston would open much more sharply as there was more force behind it.

The thing that i want to know more than anything is what pressure the vacume hose is at. From what i understand when the throttle is open the pressure on both sides of the piston are equal,... right?

Of coures if i do find that this way is more noisy, i could always just put a stronger spring on the DV

 

[max_torque]

If you are running with the std BOSCH diaphram valve then it is recommended by BOSCH that it is fitted a-la picture 1, is high pressure air enters radially and exits axially. If your running another type of valve i've no-idea!


(the BOSCH fitting suggestion is to maximise diaphram life, it makes no difference to it's operation or effect)

to be totally honest, all these people who think changing or modifiy a dump valve will have some effect are kidding themselves, it only operates during a big lift off or gear change, and you really want to minimise the length of these if you wanna get somewhere faster!

 

[LDoR]

Originally posted by max_torque
to be totally honest, all these people who think changing or modifiy a dump valve will have some effect are kidding themselves, it only operates during a big lift off or gear change, and you really want to minimise the length of these if you wanna get somewhere faster!

I kown this, DV not more power. What i do know, better DV better drive from car, i'm jus wondering which way round will give the best drive. I spose i could try it over the weekend

 

[Zamot]

Originally posted by RobDon

Left is how you'd normally install a DV, same as the factory valve, on the right is the DV reversed, work the same or better and has a louder, different dump sound! Forge said this when I emailed them asking about reversing the DV:

"They work just as good if the orientation is reversed and sometimes work better (helps reduces any boost leakage) it is just that it will be noisier."

Now you know! I've been running mine reversed for a while now and had no problems.

I don't understand why it should work better (helps reduces any boost leakage), because in fig. 1 there should be more pressure on the right side to "help" the spring..
Take a look at this picture to understand better:
20vt basics

But what does the little "box" called "recirculating valve for Turbocharger N249" do?? If this thing has no influense on the air, then it should be the same pressure on both sides, if it's reverced.

I also wonder if the hoses will reach without any kinks or un-necessary bends. Anyone who have installed it reverced who can tell? And is there enough room to do it without complications?

I think I'll try next week, and hope for a louder sound!!

 

[Feel]

Surely it's related to pressure not to flow? I mean once the pressure gets under the seat of the piston (I not to contradict max_torque as he was talking about diaphragm valves) higher pressure on one side will lift the piston up to the lower pressure on the other, nothing to do with flow.

For mounting it the wrong way round (spring horizontal) to make any difference, the flow of air would have to be blowing the piston up/open rather the pressure of the air opening the valve?

Might be noiser, why I don't know, but I can't see it making any difference in the opening stakes.

If anyone's bothered, I've got my 006P here, because I still don't have the car back yet. With my gob, I can't generate enough pressure on either of the "big pipes" to do anything (other than make me red in the face), but it's fairly easy to suck the piston off it's seat with the vacuum hose connection. I think that's telling us it's the vacuum pipe that's doing the work.

 

[MikeyH]

Originally posted by Feel
it's fairly easy to suck the piston off.

Excuse me?

 

[Feel]

I feel so dirty.

 

[-=Rob=-]

Originally posted by Feel
I feel so dirty.

That'll be Mobil 1 High Temp Grease from the Piston... :rotfl:

 

[Feel]

:spin: :rotfl:


I did spit, not swallow (it doesn't taste that nice)

 

[Deejay]

Ive tried both connotations(sp) of DV install on my ibiza 20vt.

must admit the reverse fitting of the valve made a very loud audible whoosh on mine combined with the Dynatwist,but I seemed to lose a bit of BHP somewhere along the line and approx 3psi of boost(confirmed this at the stealth RR day)

Dv is back in stock orientation now and have modded the dynatwist so I still get the whoosh factor. Boost is back to 21psi and car in general feels more alive.

Roll on Dubsport RR day(no pun intended)

Dan

 

[Zamot]

Anyone else who can tell about this trick?

Will there be any difference with org. 180 bhp, than a chipped car with about 210 bhp?

 

[LDoR]

Originally posted by Zamot
IBut what does the little "box" called "recirculating valve for Turbocharger N249" do?? If this thing has no influense on the air, then it should be the same pressure on both sides, if it's reverced.D

I think the success of reversing the DVD all depends on what this valve does.

Assuming with teh throttle open, hence the throttle valvue in the diagram is open and that the N249 valve doesn't obstruct air flow, then the pressure on both sides of the piston should be equal.

When you lift off, closing the throttle and the throttle valve a vacume would form on the one side of the valve and the pressure on the other side would push it open allowing the gas to escape back into the intake.

Of course this depends on how that valve works or what it does but from what i know of physics and mecahnics it makes sense.

 

[CupraR-Rog]

I've been running my DV as in fig 2 ever since I upgraded to a Forge valve. Tried it as in fig 1 (a la Bosch valve) for all of 5 minutes...

No power loss in reverse (in fact, RR went from 229.6 to 234.2bhp, but as it was different days...). the DV is a lot more audiable (which I like), and I've had no ill effects... must have had it in like that now for at least 4000 miles!!

Try it, it does no harm!!

In fact, I have been told by an ex- Ford RS owner, that fig 2 is how Ford fit DV's to their engines...

 

[LDoR]

Having read up about this on the Manual for an Audi 2.8 V6 Bi-Turbo the N249 valve (in the case of the V6 anyway) is used to control the acutation of the by pass valves (dump valves) indepenedently of the intake manifold pressure when attached to a reserve vacume source.

Not sure if its used that way in the 1.8 20VT but its a good bet.

Read about it here http://www.ibiblio.org/tkan/audi/