Boost guage question.

[ravenp]

Howdy.
I have a question about mechanical boost guages. Can you 'zero' them if they're off? Mine reads 4 on the vacuum side not hooked up. Hook it up and it functions right in terms of moving for vacuum to about 22 and then drops a bit as the idle drops... and in boost it does climb into the positive...

When the boost says 5psi, is it really 9? Is it just a faulty guage or can it be 'zero'd? It's a Sunpro mechanical.

thanks

[Mighty Thor]

That sounds about normal. Usually the car is under vacuum most of the time, even at idle. 5psi is actually 5.

A setting of '0' is more true for Root and twin screw blower. For us turbo and centrifugal we are under vacuum.

[grayman]

wow, no idea...but mine is at zero when car is off and when the gauge was new and in the box.

[ravenp]

I'm wondering if i could test the guage? Any thoughts on a sure source of say 10psi that i could hook it up to? Don't say my tire for 33psi :D

[Mighty Thor]

Opps, mis-understood that one. Yes, it's suppose to rest on zero when the car is off.

[ravenp]

Originally posted by Mighty Thor:
Opps, mis-understood that one. Yes, it's suppose to rest on zero when the car is off.

So you think that reading 5psi is actually 9 then?

I want to test it... haven't found a method yet.