dump valve - hows it work??

OpenToSuggestions · 25 Apr 2007 at 18:38

a friend has a glf tdi 150 and had a dump valve fitted and i just wondered how they work as im not 100% sure.
I thought they were fitted to the wastegate but im probs wrong.
thanks

sigma · 25 Apr 2007 at 18:43

http://en.wikipedia.org/wiki/Dump_valve

TaKeN · 25 Apr 2007 at 19:08

So its got an atmospheric dump valve that goes " Tisshhhhh " every time he gives it some and then backs off...

or a recirculating one ?

Lowe · 25 Apr 2007 at 19:20

They're not really proper dump valves as such since a diesel doesn't have a throttle butterfly... Just a chav add on - hell even real ones are chav add ons.

comp builder · 25 Apr 2007 at 19:39

yeah but they sound great. My uncle has one in his subaru and it sounds brilliant lol

Hate · 25 Apr 2007 at 19:42

mglover070588 said:
a friend has a glf tdi 150 and had a dump valve fitted and i just wondered how they work as im not 100% sure.
I thought they were fitted to the wastegate but im probs wrong.
thanks

gawd, a fake one

comp builder · 25 Apr 2007 at 19:44

so a dump valve robs the engine of performance through gear changes? or just generally? or not at all?

Goody_GTI · 25 Apr 2007 at 19:45

Lowe said:
They're not really proper dump valves as such since a diesel doesn't have a throttle butterfly... Just a chav add on - hell even real ones are chav add ons.

No you can get dump valves for the golf tdi engines. Forge do one Click

Goody_GTI · 25 Apr 2007 at 19:47

comp builder said:
so a dump valve robs the engine of performance through gear changes? or just generally? or not at all?

Depends what engine and dump valve it is. My golf turbo uses a re-circ valve which i have replaced with a Forge re-circ valve; these charge the air back into the engine instead of 'dumping' it into the air - (which is what an atmospheric dump valve does)

But then an atmospheric dump valve can also increase the spool up time of a larger turbo, like your uncles subaru, as excess air is dumped... i think, could be wrong with that last bit

Dogbreath · 25 Apr 2007 at 20:00

goody_106 said:
No you can get dump valves for the golf tdi engines. Forge do one Click

Lowe didn't say you couldn't get dump valves for the TDi, his use of the word "fake" means simply that it's a totaly pointless modification to make on a diesel engine. Due to the lack of a throttle, the whole raison d'etre of the dump valve is gone.

Hmm, is "raison d'etre too highbrow for this forum?

TaKeN · 25 Apr 2007 at 20:08

comp builder said:
so a dump valve robs the engine of performance through gear changes? or just generally? or not at all?

The main purpose of dump valves is to stop the turbo from stalling,

So it doesn't realy rob it

comp builder · 25 Apr 2007 at 20:11

TaKeN said:
The main purpose of dump valves is to stop the turbo from stalling,

So it doesn't realy rob it

oh i thought it was just for the cool "ttssssssshhhhhhhh" noise lol

Hate · 25 Apr 2007 at 20:24

if you think of it this way (in simple terms)

you got the turbo spinning and cramming air into the engine, when you back off the trottle theres still pressure in the intake system, so a dump valve blasts it out to air (hence the tish noise) or a recirc valve dumps it back before the turbo (mine makes a kinda flutter noise). if the air stayed in the pipes then it would push back against the blades of the turbo means it would take longer to spool up next time.

of course on smaller turbos the pressure isn't really that high to make THAT much of a difference, but some dump valves are engineered to make a bloody great noise anyway

s0ck · 25 Apr 2007 at 20:30

Dump valve on a diesel = robbing performance and completely pointless.

On the other hand, I've got an SSQV on the coupe and it sounds the bomb

agw_01 · 25 Apr 2007 at 21:08

TaKeN said:
The main purpose of dump valves is to stop the turbo from stalling,

But turbo chatter sounds sooooooooo good!

My car makes a similar noise thanks to the re-circ and big ass ITG filter!

s0ck said:
On the other hand, I've got an SSQV on the coupe and it sounds the bomb

You are a legend! I bet that gets some serious looks! SSQV's are the best sound atmospheric dump valves ever.

OpenToSuggestions · 25 Apr 2007 at 21:11

i understand the turbo, im just having problems udnerstanding the dump valve and waste gate

the waste gate diverts some exhuast away fro mthe trubo so the nturbo stays at the same speed? as i assume exhuast speed sup turbo which uts more air in engine which makes turbo go quicker and the engine would just blow.

so do you all think he has actualy LOST some hp from the dump valve add on

agw_01 · 25 Apr 2007 at 21:12

mglover070588 said:
the waste gate diverts some exhuast away fro mthe trubo so the nturbo stays at the same speed? as i assume exhuast speed sup turbo which uts more air in engine which makes turbo go quicker and the engine would just blow.

errr what?

SGCWill · 25 Apr 2007 at 21:13

I always thought a dumpvalve was designed to relieve the pressure in the intake manifold, so that when you let off the accelerator the air fuel mix didnt keep pumping, making the throttle response more crisp, and stopping it from over-reving when you change gear?

Dunks · 25 Apr 2007 at 21:17

SGCWill said:
I always thought a dumpvalve was designed to relieve the pressure in the intake manifold, so that when you let off the accelerator the air fuel mix didnt keep pumping, making the throttle response more crisp, and stopping it from over-reving when you change gear?

o_0

andi · 25 Apr 2007 at 21:17

When you lift off the accelerator in a petrol turbo, the air between the turbo and the throttle is already compressed, and needs to go somewhere. Without any DV, it will force its way back through the turbo, stalling it and potentially causing damage.

A waste gate is a valve that opens and closes to regulate the charge pressure from the turbo. Without one, the pressure may rise too high, and kill the engine.

..I think