My car regularly pulls -7 to -8 psi at idle. When I am coasting at speed, It'll go to -10 to -11 psi (max neg. value on the gauge) when the throttle is closed and the injectors are off too. I don't think that you have a problem. Just to be sure, what do your fuel trims look like?

 

-8 PSI is normal. Vacuum pressure will vary depending on ambient conditions. It is tied to the volumetric efficiency of the engine and the ambient pressure/temperature.

 

I think your confusing inHg and psi. If you were using a mechanics vac gauge,which reads inHg you would see a reading more like 18 inHg

 

My lamco gauge pod shows about -.05 mpa at idle which relates to around -7 psi. My accessport also displays psi when monitoring boost(vacuum a idle) and i get the same readout. My tuner and i haven't run into any real issues about this low vacuum, but i'm curious as to why mine is just so low without a leak. When coasting with a closed throttle i see about -10 to -11 as well but i don't know if this confirms or means anything? Maybe im just worried? I do live in the hills at about 5200 feet above sea level.. I will take a closer look at my fuel trims today. Thanks for the replies fellas. Much appreciated

 

I think you are a bit over your head here.

When coasting/throttle plate closed, the motor is still pumping air through the engine. Since you are pulling air through the same small opening as idle, the effective vacuum is much higher. This is normal. You DON'T have low vacuum.

 

I guess i should thought i'm not too familiar with volumetric efficency but if the incerdibly thin air and high elevation here can't effect it that much, does that mean that my engine is becoming less efficient thus creating less vacuum? I feel as if i should go through with the compression test..

 

Yes, that's correct.

 

Looked at your IP. Yeah you're at a mile high huh

 

ha yea, and of course my favorite place to beat my car is on our mountain which ranges from 6000-8000 above sea level
Mile high club ftw

 

Any solution ?? ... I have the same problem low vaccum to -8 and when I drive it goes up to -10...
but my problem does not end here... because of the low vaccum my BOV is opening late and that is mistreating my turbo: / please i need help!

 

Remove the blow off valve and install the actual part the car needs to start. If that doesn't solve it a BOV wont open because of high vacuum and your vacuum is normal.

In my area i vary between 600-900ft above sea level and -11 on cobbs ap was normal as was -9 depending on the day.

 

Wow this is an old thread...

 

And not yet a solution :/

 

But it's okay tomorrow I'll do a compression test and also a vacuum leak test again, so I'll tell you about it tomorrow.