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View Full Version : Engine vacuum. How much vacuum does your engine pull rolling down the freeway?



Larry Callahan
10-19-2010, 09:02 PM
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
10-20-2010, 07:04 AM
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
10-21-2010, 05:08 AM
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.