want a dump valve

[neebover]

i ran an atmospheric dump valve and i know a couple of other people who do, no problems what so ever!!!

how many of you which condem dump valves have actually tried one?

if someone wants to fit one i dont think they should be discuraged by a "myth"

this subject really nobs me off as everyone keeps going on about it and IMHO it is a load of s.h.i.t.e

regards
will

Thanks for that post, i have a turbosmart supersonic fitted and have no problems at all..

Chris

[AndyP]

Try to find out what this guy did and copy it.

http://www.youtube.com/watch?v=0hdu8...arch=audi%20s2

[Jon441cc]

Try to find out what this guy did and copy it.

http://www.youtube.com/watch?v=0hdu8...arch=audi%20s2

Thats Doug & Mihnea thrashing around knockhill

[Mutley]

Hi guys, just read the few threads about Dump valves. At the moment I have this one fitted Bailey

It has an almighty whoosh noise on changing gears, thing is it was already fitted when I got the car .Now there is no pipe running from the top bit to anywhere. should there be ?



According to this product Hyperboost it says

Is the HyperBoost diverter valve a "blow-off" valve?

No, not technically. A blow-off valve sends the "boosted" air into the atmosphere rather than the airbox/air filter. This is why they usually make a loud noise from the air releasing. This offers no real performance gain and in most all cases will cause sophisticated engine management systems, like in the VW or Audi cars, to incur errors and drivability issues.

So is the bailey the same principle as the Hyperboost ? should it have a pipe running from the top bit to somewhere and if so where. Or do I need to buy the hyperboost to be rid of the whoosh noise.
Cheers

[phil2.016v]

I had a Baily dump valve on mine Nip, I replaced it with a forge recirc valve which works much better, and I can here the wastgate chatter now :mischeif:

[Greg_S]

Mutley, there should def be a pipe to the top of the DV, it should come across behind the cambelt on a small metal pipe to a short piece of hose about 200mm long which connects to DV. the other end of metal pipe should have a short section of pipe to the front of the inlet manifold.

HTH

[Azman]

Just re read some of the statements on this thread and just wondering how is the air from the recirc measured. It can't be as it is after the MAF????? Unless it measures in reverse too??? Gone back to the turbo technics dump valve originally form wab as the standard one deformed and left me with a boost leak... Just wondering like??

[rotoryboy]

Just re read some of the statements on this thread and just wondering how is the air from the recirc measured. It can't be as it is after the MAF????? Unless it measures in reverse too???

After the MAF, It is a sealed system so doesn't need to measure in reverse

[S2central.net]

Can I try to inject some sanity in this thread...

The air entering the engine is measured by the MAF - just after it leaves the airbox and just before it gets sucked into the compressor side of the turbo.

The real issue about dump valves is much less to do with metered air being wasted than the more important advantage of reduced turbo spool times during gear changes by way of the recirculating valve allowing it to keep the compressor moving.

A dump (to atmosphere) valve is just counter productive if you look at logically... The engine needs to suck in air in order to operate. This requires time and energy - why dump all that effort to atmosphere during a gear change when you can just recycle it ?

The thing that really hacks me off is people coming on here and saying 'I want a dump valve so I can sound like on old GpB quattro rally car'... A dump valve does NOT make *that* sound... I have watched many an old UR fly past me in British forests and Irish tarmac in the 80's - I never heard one go 'psssssssssshhhhhhhhhhhtttttt' on a gear change or lift off.

If you want *that* sound then the last thing you want is a dump valve... What actually creates that sound is wastegate chatter and turbo stall. To achieve the turbo stall noise you need to remove the dump or bypass valve and seal up the hoses tight - this way the turbo will stall during gear changes... sounds great until it explodes with the stress a few hundred or thousand miles later... The GpB boys would have changed turbos for every event.

Paul

[andrewd]

Just to pick up on a couple of S2Central.net's comments ...

I believe the old Group B rally car noise being "wastegate chatter" is something of a myth. It's purely a noise caused by the compressed air being forced back through the turbine housing as it doesn't have anywhere else to go when the throttle is shut.

Secondly, the reason some of these cars didn't run with dump valves was actually to reduce turbo lag. The pipework and intercooler(s) between turbo and throttle had such a large volume that it was actually a better trade off to maintain the pressure in the system between changes at the expense of some compressor stall.

As you say, this this does cause aditional stress on the turbo, intercooler and inlet pipework but plenty of cars have come out of the factory without any form of dump or diverter valve (including some 5-cyl turbo Audis!).

[S2central.net]

Forgot to mention of course that some cars have such complicated plumbing and/or lack of space that there was no clean way to install a recirculating valve.

I can't really understand the logic of these old cars not having dump valves so as to reduce turbo lag... I'm not that familiar with the intake system of a works UR engine but there must be significant pressure built up between gear changes at WOT - so there must be compressor stall... hence the noise during gear changes.

What I suspect has happened is that Audi saw they could not nicely fit a recirculating bypass valve on the rally monsters - due to plumbing difficulties - perhaps that would have compromised lag... Then I reckon they traded off having an atmospheric bypass valve (which wastes boosted air and increases lag)... and so ended up without any bypass/dump valve. Big downside is the wear and tear on the turbo as you say... But in a works setup thats just a question of money. This perhaps aligns with your opinion that it was done to reduce lag.

I don't understand your comment about wastegate chatter -

<quote>
It's purely a noise caused by the compressed air being forced back through the turbine housing as it doesn't have anywhere else to go when the throttle is shut.
</quote>

How does compressed air (thats in the compressor housing) get into the turbine housing ?

I feel that most of *that* noise comes from compressor stall - the wastegate chatter element isn't something I can logically explain so well at this time.


Paul

[4WheelDrifter]

I had a Baily dump valve on mine Nip, I replaced it with a forge recirc valve which works much better, and I can here the wastgate chatter now :mischeif:

I would put the Bailey back on then, as it sounds like the Forge valve you have isn't working.

[phil2.016v]

I would put the Bailey back on then, as it sounds like the Forge valve you have isn't working.

Eh? It works fine, just doesn't 'woosh' as loud as the Baily

[Ross]

Just to make this thread even more exciting... wouldn't it be better to have the air re-circ after the IC? It would have been cooled before being thrown back into compressor... seems in current config it'll get heated twice. Then again, I suspect this hotter re-circ air will have been ingested by the engine by the time you've back on WOT.

It makes sense to me that a dump to atmosphere set-up is gonna be equivalent to a boost leak. If it's the sound you want, then you could scour ebay for one of those "whoosh sound" gadgets aimed at boyracers who want others to think they have a turbo'd 1.2 under the bonnet, and keep the recirc

Personally, I quite like the sound the Forge DV makes though it seems to chatter a few times on 2bar lift-off, not sure if the extra pressure means it 'stutters' like that? Hope it's not 'turbo stall'

[S2central.net]

At 2bar on such a big turbo I would suggest you do have some turbo stall... The big boys have been known to use two bypass valves to make sure all that air gets recycled.

Paul