i was consistently running 18 in Hg at ~750-800 rpm. i installed a greddy dual air intake and noticed that the pressure is now 16 in Hg. if the intake does not affect the pressure reading, then what would make this decrease? nick

 

air temp and density outside can affect it

 

Barometric pressure outside can easily make a ~2Hg difference from day to day.

 

My vac fluctuates from 15-20 depending on temperature outside. It also drops when i turn on the A/C.

 

Idle speed also changes vacuum readings. IN my experience FDs seem to change the speed at which they idle from week to week.



Jeff

 

my 20b does that too, but its more like in the morning/ afternoon



mike