Forge Dump Valve on TDI

[Zeb]

Hi all,

Im sure there was a post relating with dump valves on TDI, but cannot find the thread.

Question:

Would a dump valve be suitable for TDI? And would you be able to hear the noise when changing gears?


Zeb.

[zollaf]

a dump valve works well on a petrol engined car. when you take your foot off the throttle to change gear, the throttle butterfly closes, stopping air entering the inlet manifold and creating a vacuum within the manifold which is used to provide vacuum for things such as the brake servo. the turbo however, which is spinning and pressurising the intake air, suddenly finds itself trying to force the air into a closed intake, causing the turbo to slow down. with a dump valve fitted, this air can be vented off either to the atmosphere or back into the air inlet before the turbo. this allows the turbo to keep spooling, so that as you open the throttle you get a reduced amount of lag, and your car will accelerate faster. the pressurised air vented from the dump valve produces the sound i think you are looking for.
however, with a diesel engine, there is no butterfly valve in the intake to restrict the pressurised air from the turbo, as a diesel engine always has a totally open inlet, the engine speed being controlled by the amount of fuel being injected. therefore, a dump valve is not required at all on a turbo diesel engine, and will actually loose you power through the gears, as the turbo is having to work harder due to loosing pressure that it doesnt need to loose every time you change gear.

[Sam]

Hi all,

Im sure there was a post relating with dump valves on TDI, but cannot find the thread.

diesel dump valve upgrade. is it worth it? (http://www.vwaudiforum.co.uk/forum/showthread.php?t=33535)

F.A.O VAG TDI owners/drivers (http://www.vwaudiforum.co.uk/forum/showthread.php?t=33943)

Diesel Dump Valve (http://www.vwaudiforum.co.uk/forum/showthread.php?t=10210)

[Marco34]

Also with the turbos being VNT is negates the whole process.

[Zeb]

diesel dump valve upgrade. is it worth it? (http://www.vwaudiforum.co.uk/forum/showthread.php?t=33535)

F.A.O VAG TDI owners/drivers (http://www.vwaudiforum.co.uk/forum/showthread.php?t=33943)

Diesel Dump Valve (http://www.vwaudiforum.co.uk/forum/showthread.php?t=10210)

Thank you for sending the threads.

[Zeb]

After reading through all that, I think I will leave it and probably get it remapped when I purchase a sport Audi A4 TDI.


Thanks for your comments!!!

[Zeb]

a dump valve works well on a petrol engined car. when you take your foot off the throttle to change gear, the throttle butterfly closes, stopping air entering the inlet manifold and creating a vacuum within the manifold which is used to provide vacuum for things such as the brake servo. the turbo however, which is spinning and pressurising the intake air, suddenly finds itself trying to force the air into a closed intake, causing the turbo to slow down. with a dump valve fitted, this air can be vented off either to the atmosphere or back into the air inlet before the turbo. this allows the turbo to keep spooling, so that as you open the throttle you get a reduced amount of lag, and your car will accelerate faster. the pressurised air vented from the dump valve produces the sound i think you are looking for.
however, with a diesel engine, there is no butterfly valve in the intake to restrict the pressurised air from the turbo, as a diesel engine always has a totally open inlet, the engine speed being controlled by the amount of fuel being injected. therefore, a dump valve is not required at all on a turbo diesel engine, and will actually loose you power through the gears, as the turbo is having to work harder due to loosing pressure that it doesnt need to loose every time you change gear.


Hello Zollaf,

Appreciate the info you have provided.
I guess I will keep it as it is...

[zollaf]

your welcome. i dont like to see folk spending money on a car without good reason, or for good results and a dump valve on a diesel wont give any good result.

[Jay4]

My a4 tdi sport has a dumpvalve on it, and tbh it sounds good lol. I never thought I would lke the sound as I thought it was a bit chavy but I guess its something you get used to.
Its extreamly loud aswell and it dumps off the slighest bit of pressure, even at about 1400rpm.
The only problem being is its causing blacksmoke to come out of my exhaust when ever it dumps :( and I've been told I should take it off if I want to cure this problem, but I know the guy who had the car before me spent 350£ getting it fitted and it would be annoying if I had it taken off and it still smoked.

[B8 TDI]

The smoke is due to overfueling, it's overfueling because there is not enough air, there is not enough air because it has a dump valve.

The only thing a dump valve does to a diesel is sound good while wasting feul and degrading performance.

[Jay4]

The smoke is due to overfueling, it's overfueling because there is not enough air, there is not enough air because it has a dump valve.

The only thing a dump valve does to a diesel is sound good while wasting feul and degrading performance.

Agreed.

Do you know of anyway to solve this problem without having to take the Dump valve off?

[Marco34]

My a4 tdi sport has a dumpvalve on it, and tbh it sounds good lol. I never thought I would lke the sound as I thought it was a bit chavy but I guess its something you get used to.
Its extreamly loud aswell and it dumps off the slighest bit of pressure, even at about 1400rpm.
The only problem being is its causing blacksmoke to come out of my exhaust when ever it dumps :( and I've been told I should take it off if I want to cure this problem, but I know the guy who had the car before me spent 350£ getting it fitted and it would be annoying if I had it taken off and it still smoked.

Tell the guy to go and by a Scooby if he was noises like that! I've no idea why anyone would want a constant woosh every time throttle is released. particularly as Audi are built to be quiet and noisy in the right places.

I know you've got it now and prob got used to it. But still why do these folk do it! Each to their own I guess.

[borabeast]

My mate put a DV on a pug 306 tdi one weekend and took it off the next as it was pants.

He said it took longer for the turbo to kick in, when it did kick in it didn't have the same level of aggression.

Re-map sounds good to me.

I've got a tdi avant sport and when driven in manual or sport its very impressive already. Can't get the motto, "If it aint broke - don't try to fix it" out of my head!