why do i have to use two dump valves?

[timucin]

my friend with rs4 had a guest last week from germany,they were adding some stuff to his car, german audi expert told me to use 2 dump valves;
but didnt explain me why;
do you know the reason?

[Vagsport]

All RS4's have 2 dump / diverter valves as standard. Can't see how his could have used 1.

Siena

[Vagsport]

Except you're referring to your RS2??

Siena

[timucin]

no,i am talking about my car,rs2
he told me to use 2 dump valves

[Pisobiker]

One reason that comes in my mind right now:

On highly tuned engines, therefore using huge cold sides flowing great amounts of boost and charge, cold side impellers have a very high inertia (inertia increases proportionally to mass but with the square of the radius).
When suddenly shutting down throttle on gear changes or whatever the reason might be, this inertia of the wheel will keep on pumping charge for a short period of time (tenths of a second, probably) but long enaugh to have boost rising way higher the resistance limit of all the intake systems (hoses, IC etc.) but expecialy over structural strenght of the cold side impeller itself, potentially leading to serius damage of it.
Therefore, with big turbos, instead of having a single big and high flowing dump valve, might be better to use two smaller ones, which can also provide a quicker responce.


Marco

[Mark Halligan]

As usual, great answer Marco.

Here's a pic of the way Dahlback have done it

[Mark Halligan]

A different configuration, I did mine this way

[Pisobiker]

Forgot to say, but of course same considerations can be made for the other important function of dump valves: anti lag system.

When shutting throttle down, the sudden increse in intake pressure could just stop the impeller, therefore increasing lag when, after changing gear, the turbo has to be reaccelerated. The opening of the valves prevent the wheel to slow down too much, providing the least lag possible.


Marco

[91_S2]

A different configuration, I did mine this way

Mark,

Curious minds want to know where you stuck your air filter. Your plumbing is very tidy so I am wondering about the part that is not shown.

[Albert]

If You wold use system with 2 valves it wold be better to have one after the turbo and the second one before the trothle plate. That way You wold save the turbo and get the most presure out form the place where it is stoped just before the trotle plate. In a system where you don't have maf it and You wold have just one big blow off it should be also placed before the trotle plate.

[timucin]

i got one forgedvoo6, will get another one;
are these ok for this application?
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Therefore, with big turbos, instead of having a single big and high flowing dump valve, might be better to use two smaller ones, which can also provide a quicker responce.


Marco
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[timucin]

or shall i use two standart rs2 dump valves?

[Mark Halligan]

Mark,

Curious minds want to know where you stuck your air filter. Your plumbing is very tidy so I am wondering about the part that is not shown.

Rich,

I placed it down low behind the side grill (RS2 bumper) in front of the oil cooler. This was too low, especially for the wet climate here. So now that I have it all apart again for the rebuild, I am going to place it higher up, I've taken the air-con compressor out so it will go where that used to be.

Mark.

[NEO]

This is how it looks under my hood at the moment...

[Mark Halligan]

This is how it looks under my hood at the moment...

And this is how mine looks at the moment