http://www.edworthys.co.uk/images/pr...all%20DV26.gif

i got this on mine, its ok at the moment, i did have the original standard bailey twin piston dump valve that last about 2 years and then the spring inside snaped, i got a new one as shown above "bailey twin piston EVO" has worked fine since.

i made a tee into the pipe from the inlet to the fuel pressure reg. and the actual valve is mounted on the cozzie intercooler.

the non EVO ones dont have the little screws around the top as pictured.

dump valve
 

Hi
This is a good site lots of info,the valve i had was a single piston baily no good as it was always venting so ordered a twin piston baily from demon tweeks the guy said the twin piston is the one i require something to do with the air flow meter before the turbo all a bit tec for me:o

Thanks for all the input

Andy

basically the single piston valve stays slightly open on idle, this leaks air that has been metered by the airflow meter, thus telling the ecu there is more air coming into the engine than actually is (coz some is being leaked via the valve) so the ECU fuels for the meter amount, thus over fueling the amount of air it actually gets causing bad lumpy stalling idle. :D twin piston was designed for air flow metered cars, i.e S12, but mainly the RS-turbo, now they are a standard valve coz of reliability.

i think thats the best explaination i can give as what i was told when i got mine.

P.s you may have been better to look towards Ebay for parts like this, you can pick up bits much cheaper, only bad point is the lack of after sales problem solving.