Dump Valve & Blowoff Valve

poreilly101

Folks

A silly question here but will a dump valve or a blowoff valve leave my car any quicker?

I have a 09 Turbo Diesel that has had a remaped and is now pushing out about 190 bhp.

Do new engines all come with a blow off valve as standard?

What exactly do they do? If i fit either will i sound like a boy racer with a "shusk" sound during every gear change? I love the sound but I may not be able to carry it off! :cool:

bushy...

They basically dump the air pressure the turbo generates ( hence the sound) when you close the throttle to change gear on a petrol engine.
The idea is that you won't have to wait for it to spin up again and build pressure , probably a good idea with large turbos.

offline.seller

Pretty sure all turbo'd engines would be fitted with a recirculating dump valve. Basically these dump the gasses back into the system and prolong the life of the turbo.

An aftermarket one which would dump to atmosphere (hence the swoosh sound), you would see no performance increase in fitting one as the aftermarket systems are fitted purely for aural effect.

o/s

peasant

Your turbo already has a blow-off valve ...every turbo has one.

The blow-off valve (or wastegate) is like the safety valve on a steam engine. Once the pressure gets too high it opens and lets some of it out. There's only so much compressed air that fits into a cylinder ...a turbo at full spin produces more than necessary. Some blow-off valves can be tweaked to allow more or less pressure, not really advisbale palying with though unless you are certain you know what you're doing.

The "whoosh" valve you're talking about is a dump valve. basically what it does is open the barn door and let All of the pressurised air between turbo and inlet out into the open in one big "whoosh".

The idea behind this is: when you step off the gas (for a gearchange) the engine slows down rapidly while the turbo is still spinning fast, compressing lots of air that has nowhere to go because the engine is going too slow to use it all. So the turbo compresses air against more and more pressure, causing it to slow down and when you finally step on the gas again it's gone too slow and needs to spool up again. Opening the barn door is supposed to keep the turbo at speed. All well and good ...but if the barn door isn't the exact right size you're letting out too much air anyway and the turbo still has lag while it tries to fill the gap.
Most aftermarket dump valves just produce noise but no real benefit.

Neilw

They don't really work on diesels as there is no throttle flap to close, forge motorsport do make a diesel conversion kit but it's expensive for no benefit other then the woosh sound.

A lot of newer cars use a diverter valve which puts the excess air back into the the intake instead of to atmosphere so no woosh.

ronnie3585

But dey sound totally kewel!

JohnCleary

Not all turbos have a wastegate, my turbo has variable vanes to regulate the pressure. TBH i'd prefer a wastegate turbo - they seem like a much more simple concept hence less to go wrong

Darsad

Most of the new diesels use the variable vane type turbo as they can be easily and more accuratley controlled using the vacuum created by the vacuum pump. The vent to air dump valves used on petrol engines are lethal as they vent air Out of the intake system that the ECM and AFM has accounted for and cause the car to run rich at certain points. I have seen plenty of damaged engines fitted with whoosh valves .