Forge DV Spring?

[Jonas_R]

Emailing forge sucks, I tried emailing both forge in the Uk and in the US and I got to different answers to the same question.

[bobyboucher]

dv valve

Actualy, a dv valve is there to protect your turbo/engine from overpressure. The main purpose i believe is to release the compressed air when you shut the throttle close. All the air that was supposed to enter your engine is suddently stopped and has nowhere to go. So while your turbo is still spinning, and compressing, the dv valves open to release the overpressure. The dv valve opening pressure should be 2-3 psi higher than your wastegate control pressure.

Ciao!

[A80Avant]

bobyboucher,can you explain that about the wastegate?

[bobyboucher]

Dump valve

From Wikipedia...

Dump valves are fitted to the engines of (usually older) turbo charged cars and sit between the turbo outlet and the throttle body. When transitioning from a boosted state to a closed throttle state (as in between shifts), due to inertia, the turbo continues to pressurize air, but the closed throttle prevents the compressed air from entering the engine. In this case the pressure exceeds the preset spring pressure in the dump valve and the excess pressure is bled off to atmosphere.

Even with a dump valve the compressed air acts as a brake on the turbo (slowing it down), because the pressure on the backside of the turbo is at a higher pressure than on the front side (and the air actually wants to flow through the turbo backwards).

A blowoff valve is a more elegant solution to this problem by allowing the turbo to "freewheel" when the throttle is closed (equalizing the pressure on both sides of the turbo). Unlike a dump valve a blowoff valve can be used at multiple boost settings without reconfiguration.

Blowoff valves are sometimes incorrectly called dump valves because they serve a similar function, but they are very different solutions to the same problem.

So, I guess on Forge valves, wich are blowoff type valves, if the pressure equalize on both sides of the piston, then the spring only helps the ''reaction time'' of the valve.

[A80Avant]

ok this is what i have understood eventually.so now i cleared it up.So basically you need a fast enough reacting spring that will allow opening of the piston on idle and vaccum,and at the same time,strong enough to allow sharp closure when boost is applied.