bosch re circulating dump valves and alternatives
Turbo Mini Forums

I took the turbo mini out earlier and played with the bleed valve a bit....

it bled up to around 15 psi, though it does build boost to around 16 then drop to 15 again.

I use the bosch plastic recirculating dump valve

before I start adding restrictors into the bleed valve hoses, I believe that the dump valve isn't holding boost part its current level.

does anyone know what boost these bovs are capable of holding, and a good quality budget replacement to try instead of the bosch valve?

Cheers, Dan

I'll be fitting a Bailey single piston one on my mini. should be fine with over 20 psi.

What the mind can conceive the mini can achieve
MITP 2012 17.01 seconds 1/4 mile against "The Don"
MITP 2013 16.83 seconds 1/4 mile

double post

Edited by lee.pb on 3rd Apr, 2014.

What the mind can conceive the mini can achieve
MITP 2012 17.01 seconds 1/4 mile against "The Don"
MITP 2013 16.83 seconds 1/4 mile

needs to be re circulating and my money needs to stretch as far as possible....

What makes you think its the dump valve? Surely under load the two sides of the valve (boost and trigger) are at equilibrium so it should not leak.

More likely that your actuator is opening before you can bleed the signal off?

actuator is a -31 with a load of pre load on it. the car would only boost to around 13psi a few weeks back. replaced the std plenum (which I had packed out the factory bov), for an aftermarket one, the boost I can get now is 15psi.

as far as im aware the bosch dv will leak/bleed off boost when the levels hit around 12-14 psi??

Mine holds 17 psi

Plenty Bosch recirc valves holding alot more than even 17 psi out there in the world. There is however a version that has a tougher diaphragm that holds the higher pressures without rupturing.

There are two trains of thought. One is that it doesn't matter which way round it is plumbed, and the other is that there is only one way it should be plumbed otherwise it will leak.

Firstly though, have you tested the valve diaphragm for leaks? this is the most common issue with the bosch valves.

cheers dave. is 17 the limit on yours?

sprocket, how do I check the diaphragm? I guess there is no way that the spring rating can be changed on these?

cheers, dan

I would highly doubt the dump valve is the problem unless it is installed wrong.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Carefully insert a blunt object into the valve from the bottom and push up the piston thereby compressing the spring. place your finger or thumb over the small vacuum port on the top then remove your blunt object. The valve should hold a vacuum under your finger with the valve remaining open. The valve is damaged if it does not hold vacuum and the piston closes.

The Bosch valve is a sealed unit and cannot be dismantled. Why do you need to change the spring? the spring will always generate a closing force in any orientation the valve is plumbed, so long as you have the vacuum source from the manifold.

If you are using the same vacuum source as your wastegate actuator and the bleed valve is between the manifold and the dump valve/ wastegate actuator, you are in esence using the dump valve as a boost control function and it will open early as boost rises.

Edited by Sprocket on 3rd Apr, 2014.