Forge K03 & K04 Diverter Valve
Uprated Diverter Valve for the K04 and K03 turbos that come fitted as standard to a few different cars, in particular the Vauxhall Astra Gsi, Vxr, Z20LE* engines, and the Corsa Vxr too.
These valves stand up to the higher pressures and temperatures, that show up once you start on your quest for more go, much better than the standard plastic & rubber contraption.
CNC machined from aluminium billet, and fitted with high quality, industrial spec O-rings, they will withstand anything you can throw at them. They are also completely user rebuildable.
We much prefer to use a valve such as this over an atmospheric valve for unloading the Compressor, simply because of the factory engine control strategy. You should not allow leaks after the MAF in a Mass Air Flow based control strategy, as this bewilders the MAF and therefore the ECU. The ECU knows not of the amount of air you have just released with that massive "Tsshh", and so has to assume that the engine has just somehow consumed it under a closed throttle. This results in overfuelling at best, and quite often jerky, hesitant driving at part throttle. Not good! If you must fit a big blow off valve to one of these systems, fit a re-circulating type and plumb it back in after the MAF / before the Compressor inlet, or reprogram the ECU for MAFless / fit a standalone. MAF's don't like air leaks, no matter how good they might sound!
We think a lot of Forge at RnD, their products are great and their commitment to their customers is amongst the best in the industy. This re-circ valve is no exception, and comes highly recommended from us for any performance Vauxhall.