406oc.co.uk

Can anyone tell me where the best place is to fit a dump valve on my HDI 90??????????????? got no intercooler so no nice easy hoses to tap into

You're all but buggered, unless you fit an intercooler. Then you'll need an electronic control unit to actuate it, as standard dump valves don't work on diesels. Then you'll find it'll do nothing because there is no throttle plate to cause pressure fluctuations. Then, because the boost is set electronically, you may find you have running problems as the changing inlet pressure confuses the ECU.

It can probably be done, but it's a potential wheelbarrow full of work for no gain and possibly even a loss.

Bit of a gimmick at the best of times but as Turbo says - on a Diesel you need an electronic control system to tell the dump valve when to open. In any case with the inlet port of a Diesel just being a 'big hole' of the same volume then dumping pressurised air would be a bit of a waste having to regenerate it.

I remember seeing a place on the web who developed a system for the old 306 Dturbo - looked a lot of a mess.

This may be complete tosh, but I think I've read that boost pressure is mechanically regulated on a 90, while the others work by modulating a boost control valve - can certainly hear mine dumping excess pressure when climbing hills. [/2p worth]