I just installed a 30lb boost guage, what is it supposed to read when engine is off???
Thanks
-R

 

it will probably read vacuum.

 

If the car is off usually it would read in vacuum because that is where it is at. Thats what mine used to do until i turned the key to the on poisition.

 

It depends on the gauge type.

Electrical gauges will either have a set 'off' point.... the factory gauge simply remains at the last position it was in.

Mechanical gauges, however, will (usually) read at all times, so when the car is off, it will be reading atmospheric pressure.... on a boost gauge that will be '0' psig (notice that's 'gauge' psi, not absolute).
Also, depending on what your gauge's reference is, that might change with respect to altitude as well.

 

Cool thanks guys

 

ZERO or it's bunk. I own a mechanical gauge. That's what I know.

 

Will a 30 boost guage from a 08 work in a 06??