dump valves

Ive just read that you can fit dump valves to supercharged cars. The bloke said it wont do anything so its a waste of money, it will only make a noise. But thats all i want! It wont make the car any slower will it, because it will be releasing pressure from the supercharger? I thought that was the only down side to superchargers against a turbo no dump valve, but it sounds like i might be able to get one.

Chris, I hope you’re joking.

why? dont you like dump valves.

Oh sh!t, you’re being serious!

Ermmm… I don’t like anything that doesn’t have a purpose.
In a Noble I like the dump valves, in a Lamborghini I like doors that tilt up.
In an Elise I like the bonnet, In an Exige I like the wing and roof.

Put any of these things out of place and it’s a fake, it has no purpose.

Now, technical point of view: in a turbo it’s my understanding that a dump valve serves the purpose of releasing the excess pressure when not needed (lift off) so that the bearings have an easier life and the vane’s don’t need to fight the built up presusre on the other side.
On a superchaged car, it’s a direct relationship, although there is a pressure-limiting valve, it’s not at lift off, so I don’t think it would work.

This car is for driving, and driving hard at that.
Posing is hard on it. It may be easier on a VX220 Turbo, and that one you can fit with a dump valve.
Or a new Exige S2, fitted with the Forcedfed turbo kit.

Anyway, heve to leave you, I’m starting to feel sick…

Agreed, dump valves are only ok if they serve a purpose and generally it involves spitting fire out of the exhausts too!

Isn’t the TIE fighter-esque SC pressure releif valve enough for you?

The MSC Mr T powered car sounded like a jet fighter, even my gf commented on it

Chris, are you sure you don’t drive a nova???

Dump valves are very important on Turbo charged cars that have large turbo’s. On a cosworth running up to 450 BHP using a Garrett T34 turbo running around 32PSI (which is a LOT of boost) a dump valve is NOT required. As Uldis says they release the excess presure from the inlet tract when the throttle butterfly is closed and therfore stop that excess presure stalling the compressor wheel. And in some cases snapping the shaft that runs through the turbo (joing the compressor and exhaust wheels).

The old RS500 touring cars ran a larger T4 turbo (capable of 550BHP) and this is when the pressures involved require a dump valve. My old Escort ran a GT42 turbo (capable of 700BHP) and I ran 2 very large drilled out dump valves as we did loose a turbo on the dyno just through closing the throttle to quickly.

However Chris fitting a dump valve to your car will be detrimental to throttle responce. You are not creating enough pressure to cause a problem and any pressure you loose will have to be replaced when the throttle opens again, this obviously takes time and you will notice a drop off in inital power when you open the throttle.

All of my knowledge here is from turbo applications, I don’t have any direct experiance with super chargers, but in general as a common rule of thumb, DUMP VALVES ARE BAD!!!


Also my preference was for the recirc dump valve systems (such as toyota’s) where the dumped air get cycled back into the airbox (prefiltered and all that) so you get the go but no PSSSSSSST!

here here, recirc all the way!!! If for nothing more than to not have the boy racer chav woosh noise!!!


On superchaged cars a recirc valve do not have a big sense.
In turbo applications it is used to keep the turbocharger spinning a bit more.
With a super charger u always have pressure in the inlet mainfold, only over pressure has to be freed. And do not let this air go again in the inlet because this air is hot, fresh air is better…

Thats told me then, i wont bother. I better not mention i looked into getting Lambo doors for it then.

Chris, do what you want fella, I’m not to keen nor are other but basically [censored] 'em, if you really wanna do it then make yourself happy about it, it’s your car!

I can’t be hypocritcal after trying to fight off the roof fashists

You can even get “fake” ones that work on NA as well, so you could get something that makes the noise and doesn’t impede the running of the car IYSWIM…

If you have conviction in what you do then it doesn’t matter what anyone else says

/advise for life in general

hey RL

I heard your roof was fake…

LOL! No, not my roof, my chest hair is tho’

dont forget the sound system…


Sorry fella couldn’t resist LOL