Dump Valves

[Azman]

Hey guys I think my OE dump valve has had it so it is time for a new one,

Forge/Bailey are the ones that people seem to use to keep the standard thing going,
Anyone ever used a recirc and atmospheric in one type valve??????

Would there be any benifits to this or not? Or is it just a bit gimmicky?


Aaron

[S2central.net]

Just get a decent recirc valve... Dump valves are designed to dump the excess air that you just expended energy ingesting... A recirc valve doesn't let that air escape by presenting it back to the compressor side and provides quicker spool than a dump valve... Unless of course you have some strange desire for that 'phsssst' noise of a dump valve which I personally think is lame.

[Chris5044]

if u say quicker sool time ... then why do bigger race cars have them fitted? .. or the boys with more power?

also would it be easier to produce a flame out the exhaust if u had an atmospheric?

[Jon441cc]

if u say quicker sool time ... then why do bigger race cars have them fitted? .. or the boys with more power?

Easy fitment, also some race cars run without a BOV as the turbochargers are Expendable.

or the boys with more power?

They run the MAF on the pressure side so they don't need a recirc.

[Chris5044]

i dont get it? ... how is the maf going to prevent spool up time? what happens that is so bad for fitting this ??

[S2central.net]

if u say quicker sool time ... then why do bigger race cars have them fitted? .. or the boys with more power?

also would it be easier to produce a flame out the exhaust if u had an atmospheric?

The reason that dump valves are selected over recirc valves are due to physical packaging - especially true on modified engines where there are perhaps some drastic changes to the intake pipework such that its not possible to locate a recirc valve in a good position.

Dunno why a flame out of the exhaust is advantageous... Sure it looks cool on a race/rally car but its usually a simple side effect of a hot exhaust, sufficiently rich fuel mixture and incomplete combustion in the power stroke which allows flame propogation past the exhaust valves. Often seen on overrun.

[Chris5044]

thx for info ... "chris walks away with head down still thinking about his quiet s2"

.. how would i achieve a flame? .. bigger power? im standard with chip

[newsh]

A dump valve throws away air thats been metered by the MAF, the fuel to go with that air is still thrown in to the engine so you get a rich spot which can make a flame out the back, over richness can also wash oil off the cylinder walls, its said, so maybe increasing wear on the bores. Because a recirc valve puts the air back onto the face of the turbo it actually helps to keep it spinning when the throttle is shut between gears, ie. it keeps it spooled up.

I use a Bailey recirc valve thats been working perfectly for about 3 yrs now, it makes quite a nice noise now through the RS2 airbox.

[Azman]

And where to purchase the bailey???? Tweeks or elsewhere?

[Chris5044]

is the rs2 airbox a straight fit?

[ottawa coupe]

while not the same car, i just fitted a bailey to my UrS4 and i actually hear LESS noise than the stocker. the original DV would flutter whereas this just opens. i think it dumps the air faster due to a larger opening -> less restriction -> nothing to "whistle" on.

[newsh]

I get a nice KOOOSH noise, quite subtle but well audible, the Bailey I bought direct from Bailey motorsport. The RS2 airbox fits straight in, I didn't bother with the plastic round the back of the headlight.

http://www.baileymotorsport.co.uk/

[ottawa coupe]

I get a nice KOOOSH noise, quite subtle but well audible,

hmmm, maybe it has something to do with the different cars we have....there's a bunch more real estate between me and the DV in the S4 vs the S2 i also bought mine used from a friend...maybe a little sticky and not opening as fast as it could....

[Knight Rider S4]

I have had a Baileys on mine for 3 years and it is sticking so .....got the chance of a Forge FMDV for 40quid so bought that ..when the Baileys was working proper all you heard was ping !

Cheer