Vacuum readings and what causes low vacuum
 

what is a good vacuum reading at idle for a newly rebuilt engine and one that has 30k miles on it? I am showing 16 on the boost gauge and i have 400 miles on my rebuilt engine. i think this is kinda of low, any idea why it is so low?

the seals probably have not worn in , at about 2000 miles is when the readings should get better. as it is 16 is pretty good, are you ported?

I have brand new engine with 1500 miles and my vacuum shows 16 @ 800 rpms. I'm waiting it picks up some more vacuum, too :)

16 sounds about right. Depending on how well built the motor is, if you went with used rotor housings, etc. will affect your final vacuum.

Many times budget rebuilt motors with used parts won't pull as much vacuum as a motor with new rotor housings, etc. They'll still run fine, but they'll just be a little looser. A street port will drop vacuum down a bit as well.

Dale

mine says 20, is that good?

Yea very.

20 what? Kiwi's/km? :)

16 to 18 is great... 20 is outstanding...... mine is 16 at idle and 20 TO 22 while coasting on the freeway at 65 MPH.

Yes, once you break your motor in, it should show better vaccum. Also, your idle rpm will also help determine your vaccum at idle. (high rpm == higher vaccum)

At 800 rpm idle, i think you will find most turbo rotaries make around 16psi of vacuum. I have only seen one car pulling 20 psi of vacuum and that was my friend's low mileage 2 year old 89 Turbo II back in the day.

My car still seems to be pulling about 19-20 vacuum.. got about 91K kms..

my vac. says 19. i went and had my oil changed and they knocked off the boostsensor vacuum line and it ran bout 10. I finally figured that was the problem so i hooked it back up and running 19 on vacuum.

Variances in gauge accuracy, altitude, and engine RPM make large differences in vacuum measurements. If you are pulling 16, that's good. If you are pulling 20, I think your engine is probably healthy, but you may need an idle speed adjustment or a new gauge. :)

-Max

mine reads 16 at 900 rpms. I have a stock port reman with 3,000 miles on it.

thats why you change you own oil.