Originally Posted by scooby72 (Post 9680891)

I plump for FORGE!

Originally Posted by JAutos (Post 9680805)

Firstly i know the standard one is the best etc and also the baileys one i currently use is about as much use as a grain of sand in the desert but i am going for 350bhp with my bugeye and want a suitable dump valve that will be right for power im running etc

Originally Posted by Splitpin (Post 9680981)

The standard one should deal with that fine.

Originally Posted by Splitpin (Post 9681015)

The combination atmos/recirc valves are more than a bit pointless, as they become atmospheric during the the moments you most need them to recirculate. If you're thinking about one of those because you "like the sound", but were figuring a 50/50 one will give you some sort of "best of both worlds" scenario, you may as well just fit an atmospheric one.

OEM DV's easy and cost-effective to get hold of - so if you don't have one right now, there's no reason not to give one a try. :thumb:

Originally Posted by scooby72 (Post 9680891)

I plump for FORGE!

Originally Posted by JAutos (Post 9680927)

My thought too, but as i am going to be running high boost compared with standard i didnt want to buy one that isnt exactly right for my application. Do they only do one or are there different versions adjustable etc

Originally Posted by scooby72 (Post 9681133)

Now heres where I prob need correcting but as they are twing piston dont they just clamp more under load??
I know you can get ectra internal bits from FORGE though so there is probably what you need under one company.:thumb:

Originally Posted by QUICKSCOOB (Post 9681171)

HKS SSQV.Got one on mine.One word-AWESOME

Originally Posted by P1#1015 (Post 9681169)

The twin piston design contributes to preventing higher boost levels forcing the valve open - leaking boost pressure.

Originally Posted by Splitpin (Post 9681609)

Not really. The main purpose of a twin piston dumpvalve is to create a "Oooh, it's got two, it must be twice as good" selling point to assist the manufacturer's perfectly legitimate desire to sell stuff to people who don't really know any better.

Your suggestion that a twin piston DV "prevents higher boost levels forcing the valve open" doesn't really stand up to too much scrutiny, given that there's no good reason why a functional conventional/single piston valve should leak under boost.

Don't forget that there's a pipe connecting the the inlet manifold to the un-pressured side of the DV. When you are on wide open throttle - no matter how much pressure you run, the DV will be blown shut via pressure from the inlet manifold as well as the spring. In other words, if you are running 2 bar of boost, there will be 2 bar in the intercooler trying to force the DV open, but 2 bar on the other side of the diaphragm plus the spring, forcing it shut.

If there is a pressure differential at all, it will be whatever drop you get across the throttle body, and won't be particularly significant.

The main point of different springs and shim kits is (or should be) to ensre that the valve opens at the correct points (and stays shut at normal idle vacuum) rather than to withstand greater levels of boost. Although the best way of avoiding having to muck about with different springs and stuff is simply to use the OEM DV, which works out of the box.

Where there is a technically grounded reason to use a non-standard dumpvalve, it's less the need to "withstand" greater levels of boost, and more an imperative to dump out greater volumes of air than the OE item can comfortably cope with.