How much vac are you guy's seeing at highway speeds?

[tunethis]

I'm seeing 7-8 in.Hg of vac at 65 mph while holding a constant rpm level and 5 vac at 80mph. This doesn't seem normal but, this is my first turbo car so I really don't know. I get 18 in.Hg vac at idle so, that's good. I just want to see what kind of vac levels other's are seeing at highway speeds.

 

[silverbullett]

I try to keep it above 10-15 in.Hg at 70-75 mph for gas mileage purposes.

 

[tunethis]

I use to see about 15 vac at about 70mph a few months ago when I bought the car. That was back when I had a lot of boost leaks and a venting bov. About two months ago, I blew off a coupler and got fuel cut. After I put it back on, I noticed my vac was lower at highway speeds. A few days later, I checked my turbo and it does have some side to side play so maybe that's my problem. I'm doing another boost leak test tomorrow to see if I have anymore boost leaks.

 

[T9S1i]

Your throttle position has a lot to do with it. That also depends if you are cruising, speeding up, going uphill, downhill, flat land. I wouldnt worry too much about your part throttle vac. Just make sure its right during idle, and that your car boosts when its supposed to.

 

[tunethis]

I guess I shouldn't worry about it too much since I still get more than 300 miles per tank with some hard pulls and highway driving. I was just trying to see what other's are getting. I keep the pedal constant and the rpm's constant when I take my readings on straight road. My car is almost into boost at just 85mph; I get like 3in.Hg of vac.

 

[Defiant]

"Miles per tank" is gibberish. Do the math.