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Thread: dump valve on zlet

  
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    ashtra's Avatar
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    dump valve on zlet

    Are dump valves safe if fitted properly 2 a zlet,cus i want 1 but here so many bad stories?

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    sriturbo's Avatar
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    they are safe but there are differnt ways to pipe them up, i think most people leave the oe dumpvalve running as well as i think if you block it off you can get running problems, im sure someone else will be along to tell for sure,

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    do a search mate, there is loads of info about it.

    some people say they are fine, but some say they have a performance drop
    Black Sapphire SRi Turbo

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    I know,done the searches but dnt know wot 2 do

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    i have a Bailey DV26D on my coupe turbo, its T pieced into the Fuel Pressure Regulator pipe with a one way valve in the OE DV's vasuum pipe, drives fine, no running problems and dumps nicely!

    I did have it T pieced into the OE DV's vacuum but it makes it really jerky and not nice to drive at all

    So in my experience if you get one and have it set up as I do then you'll enjoy the nice noise and have no running issues

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    Talking Z20let Dump Valve...

    I got mine from regal,came with all fitting instructions,and was a doddle to fit,its t pieced into fuel pressure regulator line as per instructions,runs **** on,no probs at all..

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    as alraedy said... if you are deff wanting one then fit as the rest have... it to fule press... thats also where mine is done and i have never really had any problems with mine... performance wise.
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    I had miune fitted by Regal and have no problems with it
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    Courtesy of Courtenay Sport

    Dump Valve Fitting Recommendations
    This is a guide for fitting a dump valve and eliminating dump valve related drivability issues on Astra G and H, Zafira A and B and VX220 fitted with the Z20LET - LEL – LER - LEH engines.

    The dump valve for these engines must be a twin piston unit as the car has air mass metering. The twin piston unit stops the valve breathing un-metered air on vacuum, confusing the engine ECU.

    How a Dump Valve Works
    Traditionally a dump is fitted in the boost pipe close the inlet manifold; it has a vacuum - boost trigger pipe taken from the inlet manifold between the throttle body and the engine. When driving the car hard on boost there is boost pressure pushing on the dump valve, however there is equal boost pressure pushing on the dump valve diaphragm on the other side. This holds the dump valve shut in equilibrium. When you lift off the throttle the throttle body closes this creates a vacuum in the manifold thus in the boost – trigger pipe, this vacuum pulls on the dump valve diaphragm and with the boost pressure in the inlet pipe pushes the valve open releasing the air into the engine bay with a whoosh.

    How is this Vauxhall Engine Different ?
    These engines work as above, with one major difference. The boost - vacuum trigger pipe is run through a vacuum storage capsule, and a solenoid that is triggered by the engine ECU. There are switches on the pedals so the ECU knows when you de-clutch and trips the solenoid to create the vacuum quicker to the original equipment recirculation dump valve built into the side of the turbo.

    This vacuum solenoid arrangement is also used on part throttle to regulate the air mass to the engine, i.e. when the turbo is trying to make boost due to its small size but the load demands and throttle angle do not require boost, it opens and shuts the factory re-circ valve to regulate boost improving drivability, kind of like a secondary throttle.

    This is the source of the trouble. If you use this trigger source (i.e. from the original vacuum storage) for the aftermarket dump valve it will pulse the new valve on part throttle, the previously metered air is then released into the engine bay and will cause driveability issues on the fuelling. In some circumstances the car will also go lean, in this situation the TC (traction control) light can come on.

    The Fix
    The cure is to give the aftermarket dump valve its signal from a true non interrupted vacuum source; we recommend the fuel pressure regulator (see picture below). For further improved driveability, it is possible to leave the original equipment valve still working so the engine management can regulate, control and pulse this valve. However the aftermarket valve will operate slightly quieter.

    Fuel Pressure Regulator Location



    Fuel Pressure Regulator (arrowed) showing take-off point for a vacuum feed for an aftermarket dump valve.
    For Astra G and H: The fuel pressure regulator is located at the left hand end of the fuel rail when viewed from the front of the car. It is partially obscured by the cross-over pipe.
    For VX220: The fuel pressure regulator is located at the right hand end of the fuel rail when viewed from the rear of the car.
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    courtenay fitted mine and had no trouble at all.

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