Engine vacuum. How much vacuum does your engine pull rolling down the freeway?

[Larry Callahan]

I have always suspected the vacuum gauge in my dash was wrong. I'm running twin turbos and a can that should pull a lot of vacuum but I doubt in the high 20's on flat level ground at 65mph.

When going down hill with the throttle closed it runs very very close to 30"

Does that sound right?

[camcojb]

I have always suspected the vacuum gauge in my dash was wrong. I'm running twin turbos and a can that should pull a lot of vacuum but I doubt in the high 20's on flat level ground at 65mph.

When going down hill with the throttle closed it runs very very close to 30"

Does that sound right?

I never saw more than 22 or so on hard decel with my twin turbo.................. and that was with the stock LS2 cam that made 19" at idle............. Think I had close to 20" with the larger turbo cam on decel, made about 13-14" at idle.

Jody

[my72vette454]

Mine idles about 13-14 and at 75 down the freeway about 15. I am at about 5000 feet elevation and I think that makes a slight difference on how much vacuum you can pull.