i was wondering if it is possible to fit a dump valve to a turbo diesel engine without messing it up. any one managed it?

You'll probably find it already has one my dad's Passat pd has. BTW don't be fooled into thinking that a dump valve gives you extra horsepower it won't it simply allows the turbo to spin up quicker giving you a bit more throttle response & increased reliability for the turbo. Also the dump valve might not work if your car hasn't been chipped or remapped. A quick tuning solution is to turn the actuator up 2 turns(no more).

Dump valves are designed for petrol engined turbo cars. A diesel engine runs with a wide open intake all the time, with no throttle butterfly like a petrol engine, so there's no 'brick wall' for the turbo to be suddenly pushing against. The point of a dump valve is to release excess pressure and prolong the life of a turbo, they're not needed on and can actually slow down a diesel if you manage to fit one.

I can't see them slowing the engine in any way because they are not powered by the engine & they don't restrict flow in the intake manifold. But as I already stated diesels do have waste gate's fitted my dad has one on his Passat which came from the factory.

i thought dump valves evacuated excessive pressure.... which i wouldn't think would be a problem in a TDI since its the pressure stroke that important??

A dump/blow off valve or wastegate releases excess gases from the inlet manifold. & as far as I know the only turbocharged engine you can't fit a dump valve to is a suck through turbo which have'nt been used since the Renault 5 gordini turbo & mitsubishi lancer 2000 in the early 80's.

Ah. Wastegates and dump valves are different things.

A wastegate is a bypass device built into the turbo itself, designed to limit the maximum pressure the turbo can create. What it does is effectively bypass the turbo's exhaust side impeller so it doesn't spin it as fast and create as much boost pressure. It isn't connected to the intake.

A dump valve is fitted to the intake side of the engine. What it does is vent off all pressure from the turbo when high vacuum is sensed in the intake - i.e. you've closed the throttle. When you close the throttle in a petrol engined car, you close a valve in the intake which the turbo tries to blow against - this can stall the turbo and cause excess wear as it's trying to push air where it can't go. A dump valve would open and vent this pressure, allowing the turbo to slow down in it's own time rather than being forcibly slowed.

A diesel engine doesn't have a throttle butterfly, the intake is always fully open. Diesel engines dont work the same way as petrol ones with regard to weak and rich mixtures (yes, you can still overfuel and smoke though) so there's no need to limit the air coming in - the power delivered is controlled by the amount of fuel injected.

Fitting a dump valve to a turbo diesel is a job in itself. A conventional dump valve is vacuum operated, and will never open as there's no vacuum created in the intake side. If you do manage to fit one, it CAN slow the car down as you may induce turbo lag - there's no need to vent the boost pressure on a Turbo Diesel, if you do so the turbo will have to spool up again to create more boost again when you floor it in the next gear. If you don't slow it down, it won't have to speed up again.

Dead right with the suck through turbos and no dump valves - the way these are designed the turbo sucks through a carburettor, so you've got fuel and air mixture in the boost line - you don't want to release this under pressure in the engine bay as you might just go up in flames!

fixitagaintomorrow said:

Ah. Wastegates and dump valves are different things.

A wastegate is a bypass device built into the turbo itself, designed to limit the maximum pressure the turbo can create. What it does is effectively bypass the turbo's exhaust side impeller so it doesn't spin it as fast and create as much boost pressure. It isn't connected to the intake.

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A dump vavle & wastegate are the same thing the unit you're thinking of is the actuator which allows you to fiddle with the boost.

bennyboy66 said:

A dump vavle & wastegate are the same thing the unit you're thinking of is the actuator which allows you to fiddle with the boost.

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Actually you're wrong.
The dump valve and the wastegate is not the same thing.

fixitagaintomorrow is correct in his description of the dump valve and the wastegate.

Actually I'm right! I have experience of tuning turbocharged engines. Mainly Volvo's.

I'm looking for info about turbo on net and came across this article:

http://www.auto-extreme.com/showtecharticle.php?id=13

It describes the different things relating to a turbo.

I'll see if i can find some more info.

bennyboy66 said:

Actually I'm right! I have experience of tuning turbocharged engines. Mainly Volvo's.

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I'm sorry, but if you read the article Santa mentioned it says otherwise.

thanks for all your help i think i will leave messing around with the turbo for another day and just get it chipped. cheers