Ok so I just installed a new vacuum pressure gauge on my 2.2Ohv... I t'd into the medium sized vacuum line right off the back of the throttle body. Now when I start the car the guage reads "0" at idle and when I open the throttle it jumps up to like "12" or "15"... Shouldn't the vac pressure be higher than "0" at idle? is it the hose I t'd into? What would be a correct reading?

I always thought cars had most vacuum at idol myself...




Tunned by Innovative Tuning

Idle: 16-20 inHg
Decel: 18-24 inHg
WOT: 0 inHg (N/A)


2001 Olds Alero (LD9)
650 whp / 543 ft-lb
@turboalero

Thanks for the numbers ion... Shoot! Im not getting those numbers at all. at idle the needle just sits at 0 til I press on the gas then it jumps up to 10 or 15 then right back down to 0 once the throttle is closed... IDK maybe its the line I T'd into giving me a different reading than usual...

The line you tapped into is actually taken from in front of the throttle blade. Tap into the line that goes to the fuel pressure regulator, that source is from behind the throttle blade and should read correctly.

Good stuff MadJack! Thanks a lot I'll try that!

[ion wrote: C2]Idle: 16-20 inHg
Decel: 18-24 inHg
WOT: 0 inHg (N/A)

This is a pretty good base to go by. You can tell alot by a vacuum gauge. One thing that is missing is that the gauge needs to be STEADY. If the gauge moves, even the slightest bit your motor is not running perfect. Now there are different reasons it could not be running steady but on a factory car it should be very steady. Also with the air on, it will go from 20hg at idle to around 18-15. Just because your putting load on the motor.

Also one big thing, if your using a cheap gauge from autozone that cost $10, you are not going to get a good reading, I only run autometer gauges.

Mark


http://www.overkillengineeringmotorsports.com/