Forums Forums Enthusiast Forums A - Z Autowirral dump valve

just wondering if any one could reckonmend the best make of dump valve to get, of if they have any point about fitting them

ie( they are sh#t or they are fab)

cheers for your help

revotec do a cheep group a dump valve for 65 quid from d tweeks
cant be that bad as it's group a

You can also look for Bailey, or Forge.

Some make more noise than others.??

Tim

what is the group a for? racing cars dont have dump valves do they bacause I think they use the recurculating ones! what car is it to go on go go gadget? I have the collins one on my car which is designed for the escort cosworth which mine has the same turbo as! mine bolts straight to the turbo so no cutting and faffing around! I think the scoobys have a simalar set up where the dump valve bolts in a certain place!

speak to a specialist tuner jim as read somewhere that the A4 doesnt like after market dump valves cos it confuses the ecu etc makin it run not right.Just thought id share that before you spend cash mate (like the boost valve) ha ha

Its to do with how your car measures the air entering the engine.

Some cars require a piston type dump valve as the diaphram ones tend to leak under vacume, and mess the reading up for the cars MAF sensor.

A Recirc valve puts the air back in to the inlet, so the air it has measured passing over the MAF is always in the system.

Atmospheric valves get rid of this air, and as its after the MAF, the ECU has an incorrect reading of the air in the intake. Some cars can cope with this air loss, others cant and run like a bag of poooooo

the air is bypassde back to the intake b4 the turbo so the air is not in the system so this should not effect it at all! and all dumpvalves tend to leak under vacuum as this is how it is opened to vent the air! the throttle closes and there is a vacuum between the inlet manifold and the throttle this opens the dumpvalve and vents the air that is between the turbo and the throttle!

.....so the AFM (MAF sensor), just after the airbox measures the air - hence it knows how much is after this.

Re-circ valves recirc the air between the AFM (MAF Sensor) and turbo and the air that was originally measured is STILL in the system and not been "dump'd" from the system, and not put back before the AFM to be remeasured.

Get rid of this air without the AFM knowing about it - your gonna get problems of overfueling as the ECU thinks there is more air in the system than there really is.

Like I said though, most cars can deal with this, but some (tend to be the latest cars) need an exact measurement of the air in the system.

For the other cars using an MAF Sensor, a piston type is generally sufficient. Piston dump valves should also NOT leak on vacume. They have a light spring, which means on equal pressure it is held shut with the spring, but when you close the throttle and get pressure on one side of the throttle butterfly, and vacume on the other, this vacume is strong enough to open the valve and dump the air - thats why bigger power (higher boost cars, most commonly Cosworths) need to uprate the spring in their dump valve to cope with the pressure change better.

why do other cars have these add on put on there car's?

wouldn't it be easy if all cars were made the same way?

i mean they do make the car good faster don't they?

i know they make a hissin sound when you floor it an release the pedal.

What i am trying to ask is in the long run would it damage your engine?

TBH a DV slows your car down

Every time it dumps, it empties all the boost pipes which must be filled again on throttle up before the boost can kick in - ie, a DV increases lag between gears.

However, it does protect the turbo. Once you shut the throttle, the turbo is still spinning, and still rams air at the closed throttle housing. Having no where to go, it goes back through the turbo and out through the air filter - causing the turbo to stall and puts a lot of strain on the bearings of the turbo.

For this reason, rally teams and seriously tuned cars run "Anti Lag" rather than a DV

If youown a turbo diesel car, don't make the mistake of buying one a dump valve, you won't be able to use it.