TRD boost gauge, how to read?

[delrmx01]

This maybe a dumb question -- how the hell do I read this ?? I know that it also measures the actual vacuum while idling , then past 0, is that how much boost it is ? so when I'm idling the gauge is always at 20 psi or when I'm not stepping on the gas ..is this correct ??

Thanks for any input --

Mel

[delrmx01]

Nevermind ....I figured it out. 20psi is normal ---that's vaccuum -- as for the boost , anywhere from 4-7psi right ?? But , what if my gauge goes past 7psi when I floor it --is that normal ? I know that too much boost could damage the engine ---I have to keep an eye on it again ...cuz sometimes I think it does go past 7psi..

[mjjoff]

the number below zero is the vacuum pressure, once past zero that is boost pressure. I've hit 8 psi of boost on one of my runs so i'm pretty sure its normal, I'm not worried about it

[arkie6]

Originally posted by delrmx01
This maybe a dumb question -- how the hell do I read this ?? I know that it also measures the actual vacuum while idling , then past 0, is that how much boost it is ? so when I'm idling the gauge is always at 20 psi or when I'm not stepping on the gas ..is this correct ??

At idle what you are seeing is engine vacuum, not boost. This is normal. On a normally aspirated engine, this vacuum will approach zero as you go to wide open throttle. However, with a supercharger, which provides positive boost pressure at higher RPMS, you will go from a vacuum condition then pass through zero and continue into positive pressure indication. Also, engine vacuum is typically expressed in inches of mercury or inHg, and 20 inHg is a fairly typical vacuum reading for an engine in good operating condition at idle. Once you pass through zero, boost pressures are typically expressed in pounds per square inch or psi. Seems like I remember reading that the TRD Supercharger is rated for a maximum of approximately 6 psi boost.