I've run one of these dump valves now for a few years and have always found the boost response to be a little bit jerky around 3,000 rpm. The spirng that they come with as standard is blue. They also have yellow and green springs. Blue is the hardest, and green the softest.

On thier advice I changed the spring to green (which they reccomend for up to 24psi) and the throttle response is soooo much smoother and there's no chatter when I lift off the throttle at low revs.

i've also done the same recently, hell of an improvement

yup - I'm on green too - makes the car much easier and smoother to drive, especially on light boost

Any issues with the DV leaking when you are running 1.5 bar + Nigel?

mine holds boost fine, running 1.3 bar

I've recently changed to an HKS ssqv, from a Baileys , and I noticed the exact same thing. She's *so* much smoother to drive on light boost...

When i bought my Forge dv i got myself a spring kit also.
I've always run the std spring but i'm going to change to another spring & see how it goes.

Si - no leaks at all - I can run well over 1.6 bar with the green spring

Note that the spring rating quoted by Forge is nothing to do with boost pressure - the Forge guy did explain it, but I've forgotten what he said

Note also that one of the reasons that the Coupe can run the lightest spring is because the DV orientation is so that the side port of the DV is facing the pressure - this means the DV can't easily be forced open

He explained it to me too - something about the intake manifold pressure differential..... got lost soon after that. The conclusion of the conversation was that I would try the green spring, and then pop a different one in if I was not happy!

i have a bailey dv26 ut was thinking of changing, sorry to go of topic here but i was wondering if its plumbed in correctly as i have just put new turbo on and dont want to wreck it. it has a blank on the turbo inlet hose about as big as a 10p, then the dv connects upwards to the metal pipe above.(the boost hose going into the inlet manifold) is this correct?

reason i ask is that it has become aparent that the previos owner was a numpty and he installed it.

also how would i convert to a recirc, would i just add piping of the bottom the blank on the turbo inlet hose, and then conect to recirc?

Having got the Forge "Tuning Kit" I've changed to the green spring but I'm still getting "chatter" when lifting off boost.

I had this problem with a HKS fitted too which is making me think it isn't the DV but possibly the SIP / Apexi combination?

Any thoughts / suggestions most welcome as I'm seriously considering going back to the standard airbox and routing.

Does it chatter whenever you lift off - or just at about 3,000 rpm when you are building boost? If so then this is normal to a certain extent - you can just hear it more with the SIP.

I've been fiddling about with mine too and put the red one in as the dump valve was dumping air when i am feathering the throttle coming out of slow speed corners. It's green, yellow, blue then red, yes??

Nigel can you explain a bit more the theory behind the softer spring working please. If this is correct then maybe i have goone the wrong way with spring selection. If it's dumping on part throttle do you not want a stiffer spring so that it doesn't dump?

It happens whenever I lift off or change gear to some extent. It's more noticeable at 3K revs but as you say I'd expect that. Didn't realise a SIP had that side effect - it'll be going if it does.

@ Sparco - Marco for a full explanation on the springs, give Forge a call; they'll give you as much technical detail as you can handle. They lost me after the first sentence but that's not unusual.

Oh and the spring colour order was right.

Forge Motorsport; 01452 380999

When you swapped springs did you check the d/v diaphragm for any splits???
Thats why i was getting chatter, as soon as i replaced diaphragm with uprated kevlar one the "whooooooor tish" was back!!

Nick

Forge very kindly sent me a free DV overhaul kit with the tuning kit so everything's new inside and the chatter is still there.

The forge DV does not have a diaphragm.

Sparco - The spirng that they come with as standard is blue. They also have yellow and green springs. Blue is the hardest, and green the softest.

So is it just the dump to atmosphere d/v's that have a diaphragm???
How does the dv006 work then???

Nick

forge DV uses a piston

DVs can use one (or both) of two methods to dump excess intake pressure

1) when the pressure in the intake manifold exceeds the pressure required to open the DV, the piston (or diaphragm) in the DV opens and releases the excess pressure back to the low-pressure side of the turbo (but still upstream of the AFM)

2) When the throttle is lifted (not necessarily closed) and vacuum is created in the inlet manifold (between the throttle butterfly and the intake valves), the vacuum lifts the DV piston which opens the ports to allow venting of the excess boost pressure. The lighter the spring, the easier the DV is actuated with lower levels of vacuum. This doesn't cause boost loss, but makes the actuation of the valve easier, which in turn makes for smoother driving, especially at low boost levels.

Because the Coupe uses the vacuum actuation, there is no requirement for a heavy spring to keep the DV closed. This is also the reason why the Coupe uses the DV in an orientation such that the side port of the DV faces the boost pressure. If you get the orienation wrong, the boost pressure can open the DV without vacuum, causing loss of boost pressure.

Are there any spring options for the Bailey DV26?

Is this low boost awkward 'dumping' related to compressor surge as demonstrated in the Synapes DV videos? I find my turbo very on/off when driving at low speeds and am currently looking for a fix...

I have a DV26 on my car as I found it worked fine straight from the box. Maybe the piston is dirty or sticking.

the dump valve was dumping air when i am feathering the throttle coming out of slow speed corners.



if your feathering the throttle (pressing the accelerater then letting off) it should be dumping air.

i run the weakest spring @ 1.3 bar with the sip & the car runs perfectly, when i had the stronger spring in, the car would really judder when letting off the gas or feathering the throttle

Thank Nigel/Joel i think you have cleared this up for me a bit.

Simon i have a red spring in my kit too which is stiffer than the blue spring?

Anyway i require a certain degree of feathering as otherwise my car will spin up out of the slow corners when i am trying to put almost 400bhp down. With this in mind and going on what Nigel and Joel have said i'll try the green spring back in again and see how we go.


Thanks guys.

I'm not sure about the Red spring TBA - they gave me a kit which was Blue, green, yellow. Does it feel more substantial than the Green? If so then I would think it's the strongest - but you can always give them a call to check.