I have a VDO turbo boost gauge installed in my car which was done by previous owner. The gauge reads both (in Hg) and (PSI). When I start the car it goes to 20 in Hg at idle. Is this correct? When I get on the throttle the needle goes past the 0and goes into the PSI area of the gauge. If someone can explain this I would appreciate it. Im not sure the gauge is hooked up right. I have already fixed the oil pressure gauge which was wired incorrectly that is why I am questioning this gauge. I never dealt with a turbo before. thanks for any help could not find any infor at VDO site.

 

Yes, the gauge is functioning properly. At idle you will be in vacuum (below 0). you will also be in vacuum at a light throttle cruise and in heavy vacuum if you are in coasting down in gear. You will only see boost on the gauge when you are accelerating.