Will this give my Supercharger a whoosh?

AS you all by now, I spend far to much money and still have little or no knowledge of anything mechanical.

VF-engineering sell a Race Bypass Valve for the Vortech Charger I run. Is this the same as a dump-valve? Or have I just got the wrong end of the stick as usual?

Description:
This valve is a direct replacement for the Bosch valve as used on most German factory built turbo automobiles eg VW Golf 1.8T / Audi TT / Porsche 911 Twin Turbo. The Bosch valve is made from plastic and contains a rubber diaphram which is acutuated by engine vacuum. The valve is used to release pre-throttle body manifold pressure on deceleration.

The VF-Engineering Race Bypass Valve is made from billet aluminium and can withstand higher boost pressures and the higher charge temperatures. The OE Bosch valve is a part that is prone to failure in stock applications and particularly on 'chipped' vehicles. Bosch have revised their valve design several times but by using the VF-Engineering valve you will have the assurance that once this valve is fitted, it will not need to be replaced.

The VF-Engineering Race Bypas Valve has been bench "flow tested" and results show that it flows just over 10% more capacity. The greater airflow capacity means that on aftermarket and higher boost applications, air turbulence is reduced and the possibility MAF turbulence is minimized.

This valve is supplied with all VF-Engineering stage 2 supercharger systems and is recommended for all stock and modified vehicles fitted with either superchargers or turbochargers.

 

it looks like a replacement recirculating dump valve, made from aluminium. the mk4 1.8t bosch one is known for messing up as its made from plastic. I'd find out what one u have on your car first (if u have one) and go from there.

EDIT, i think some recirc valves give a slight whoosh (not like a non-recirc valve though) recirc valves are generally quieter as they dont expel as much air to the atmosphere. I think they sound louder with a drilled air box though.
Edited by: S1MMA

 

Drilled air box dude? I have a Supercharger.. with a f**king huge K&N on the end of it.
Edited by: eViL

 

Stage 2 kit eh?

 

You don't need a dump valve with a supercharger.

 

So is that what it is? A dump-valve?
Edited by: eViL

 

Yes, but it recirculates it back into the intake instead of venting it off to atmosphere.

 

So what difference does it make whether it's vented off or recirculated?

 

If it's recirculated, then theoretically you're not losing boost. You're just pumping hot air back into the engine.

 

Actually.... with a dump vavle the boost is vented to atmosphere to help the turbo remain spinning between gear changes while the throttle valve is closed. Other wise the pressure backs up to the turbo and acts as a brake and reduces the turbos rpm's. A recirculating dump valve achives the same effect by looping the boost from the turbo outlet back to the turbo inlet which keeps the turbos speed up.
With the G60 supercharger neither is needed because the throttle body has a bypass valve which feeds the boost back to the G-ladder when the throttle is shut. This is is mainly to allow the engine to idle because the G-ladder produces boost even when the engine is idling.
If you just want the chuff sound of the dump valve on your G60 then you need the one that vents to atmos and plum it in between the intercooler/chargecooler and the throttle body, it won't effect the engine performance but you will get the chuff sound.

 

he doesnt have a g60 he's got a vr6 with a vortech s/c!

 

so.. can I get a chuff sound on MY supercharger?

 

shouldnt think so, because a supercharger is never off boost like a turbo. so if a g60 wont do it then a vortech probably wont either. not that i've ever tried it of course!

I have heard the effect of fitting a dump valve to a g60 - it doesnt chuff, it whoooshes constantly until you floor the accelerator!

 

A mate of mine has one on his G40 and that sounds well good. You have a point though it does hiss on over-run but when your gunning it and changing gear it sounds sweet.
Edited by: G60 Matt

 

hmmm.. interesting. Surely he's losing boost this way though?

 

not really losing boost, its boost that wouldve been recirculated back to the charger anyway, because youre not running it at full throttle it doesnt need that much boost. but youre not gaining anything as far as I know.

I think there is something called a jiro valve that has the opposite effect, it stops the boost venting at light throttle openings, making the car more responsive mid range because there is full boost more of the time.

 

I'm only in it for the sound to be honest. Couldn't give a poo about extra performance. As long as I don't lose anything..

 

A recirculating dump valve is mostly used where dumping the charger air to atmosphere would lose metered air - that is, air that has already been measured in the ECU by a Mass Air Flow meter. Losing this air to atmospehere would cause incorrect fuel/air ratio - make it run rich.

The valve is driven from the amount of manifold pressure seen after the throttle body.

At idle and part throttle settings there is (generally) a partial vacuum in the manifold. At these times, the valve would remain open and recirculating the air from the charger outlet back to the charger inlet.

At wide open throttle the manifold pressure is near to atmospheric then goes positive as boost comes on. At these times the valve shuts tight and so no boost is lost back to the charger inlet - its all going into the manifold/engine.

With a supercharger, whether a positive displacement type (G60, Eaton etc) or Centrifugal (Z-Eng, Vortech etc) the air would be recirculating all the time there is a part throttle setting. As soon as you gun it, the valve shuts and all the boost enters the engine. Change gear quickly, and you will get a chuff as when you let go of the throttle, vacuum happens in the manifold, valve opens, vents - you get the picture.

So the choice of using a recirculating dump valve, or an open to air one, and where to locate it, can be made by looking at your charger setup. As long as you start metering the air entering the engine after the 'loop' or open part of the circuit, you are OK - otherwise, like I said, you will lose metered air.

NOW - heres something to bake your cookie:

Would fitting a recirc valve to Centrifugal Supercharger setup (Vortech, Z-Eng etc) cause more drag on the engine? Doesnt it go that load on the Supercharger is directly related to air flow through it - so increasing the flow will increase the load?

Think about a hair dryer - cover the exit nozzle up with your hand (make sure its on a cold setting!) and you will observe that the motor inside races faster and faster. Thus you have reduced the flow, the load on the motor dropped, so it went faster. Let your hand go, and the motor slows down as its now flowing air.

Work that one out!

Jules
Edited by: jcorallo

 

Er.. so does that make the recirc valve a good or bad thing?

 

i think what some ppl are forgetting is that a turbocharger forces air when exhaust gasses are flowing (ie asking for more air) so therefore when there is no exhaust flow the turbo is bein held up and stalls. hence the need for a dump valve, to ease pressure on the turbines. whereas on a s/c setup, the charger is running from the pulley, hence always forcing air. so when your off the go go pedal, with no exhaust gasses flowing the charger is slowing down as the engine rpm does. hence no need for a blow off valve, but there is a wastegate on the charger which when the inlet gasses are too high vents the air, which gives you a tsh tsh tsh noise. these will also stop you from over boosting and blowin pipes etc.. im probs talkin out my ass here tho. lol