Idle Vacuum

[slowvt]

A few weeks ago a friend lent me an Autometer Phantom Vacuum/Boost gauge to try in my car. It read around 20 - 22 in Hg vacuum at idle and around 13 psi peak boost - with what is supposed to be a 10 psi custom tune. I have since fitted a Stewart Warner gauge as it looked like a better match for the other gauges. It reads around 17 - 18 in Hg at idle and 10 psi peak boost. I thought I may have had a leak in the hose somewhere so I reconnected them temporarily on a short hose under the bonnet using all the same connections and still got the different idle vacuum readings. Which gauge is right? What is a normal idle vacuum reading for a BA MKII manual?

[YPURV4]

A few weeks ago a friend lent me an Autometer Phantom Vacuum/Boost gauge to try in my car. It read around 20 - 22 in Hg vacuum at idle and around 13 psi peak boost - with what is supposed to be a 10 psi custom tune. I have since fitted a Stewart Warner gauge as it looked like a better match for the other gauges. It reads around 17 - 18 in Hg at idle and 10 psi peak boost. I thought I may have had a leak in the hose somewhere so I reconnected them temporarily on a short hose under the bonnet using all the same connections and still got the different idle vacuum readings. Which gauge is right? What is a normal idle vacuum reading for a BA MKII manual?

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Hey mate my stewart warner gauge read the same 18-19 in hg and 10-11 psi, so unless booth our cars a wrong I think she's sweet mate, mine is a mark1 auto

[ZAP]

the cheaper the gauge to less accurate the readings.

Also it would depend on if it is electornic or analogue.

My Apexi EL2 elec gauge would read about 18hg on idle and was always spot on for the boost.

Your idle readings will also be different if it is a cold start or if the aircon is running as it changes the idle.

[slowvt]

Thanks for the replies. Accuacy is not all that important to me as long as it is consistent it will alert me to any unexpected changes in boost.