Speed Density Vacuum question

[5.0Flareside]

just for reference about how many PSI of vacuum does the Speed Density like to run off of?

 

[89PSD]

you will get a maximum of 0 psi, it all depends on how much the throttle body is open. An shut throttle body creates a vacuum behind it, due to the engine sucking air, Full throttle there is no restriction and 14.7psi of atmostphere air is dropped in. unless you got something forcing air in...

14.7psi is the weight of all the air above your head at sea level forcing down in one square inch. The reason why one would not notice if you were to hold a boost guage in your hand and expect to see 14.7psi on it- is because most guages arnt calibrated to read zero in a vacuum.

so I would assume it would run off 0psi and under

 

[conanski]

Vacuum is typically measured in inches of mercury or kilopascals and the SD EFI system wants to see a very steady and strong vacuum signal at idle to function properly.. in the range of 16+ in/hg or 54Kpa.

 

[flareside_thunder]

I always thought it was 21 in/hg.