I have chosen on my 850 to replace the standard recirculating valve on the turbo for an atmospheric dump valve. There are two reasons that I've done this. Firstly - and very importantly - it sounds fantastic! Secondly - it does seem to ease compressor stall and keep things spooled up nicely.

It is very important on these cars to properly disable the re-circ valve before fitting the dump valve - otherwise you have two devices trying to do the same job and this doesn't work so well. Also - the OE re-circ valve does not offer any adjustabilty.

I chose a forge dump-valve as part of a kit from Kalmar Union. The Kalmar kit is the only one I know of to include a blanking plate to go on the side of the turbocharger to properly replace the re-circ valve and make the dump valve work as it should.

The kit also includes a silicone hose with a T-piece to accomodate the valve and control pipework.

Above: The Kit as supplied, and the kit in situe in my engine bay. Note the induction pipes are lagged for cooler airflow.

The dump valve connects directly to the vacuum tree on the throttle body, disconnecting the re-circ control line. There are those who are concerned about dumping metered air to atmosphere - and that it would cause fault codes in the ECU but in my experience with this mod - this just hasn't been the case with the T5 engine. I've been extremely pleased with this mod - and would highly recommend it.

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