My Car's Pulling 20 Vacuum at Idle
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#9
OG
it's usually a good sign to pull 15-16 at idle (750ish)...but porting ..airpump and other mods can change the vac. Nothing replaced a compression test...
I for instance pull 490 on the PFC sometimes 510...sometimes 450...
depending on I dont know what...car always pull hard and strong
I for instance pull 490 on the PFC sometimes 510...sometimes 450...
depending on I dont know what...car always pull hard and strong
#11
Vagina Junction
Join Date: Mar 2001
Location: Seattle, WA
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Also it depends what your mods are. Air flow mods (intake, IC and exhaust) will drop the idle vacuum down. With intake, IC, DP,MP,CB, i see about 13 psi at 740 idle. Runs like a champ.
~Tom
~Tom
#14
Meesto Spakaro
Join Date: May 2001
Location: Redondo Beach, CA
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I have a ported motor as well and I pull ~15 @ 800 rpm.. at first I was concerned that I was getting low vacuum, but since im ported and have some intake and exhaust mods, i think it is normal?
#15
Haven't we ALL heard this
I also think that atmospheric pressure will affect your readings to some slight degree.
Not that I care....but an engine at idle produces a vacuum. Not pressure. So, any idle vacuum reading is just that (Vacuum being messured as Inches of Mercury (HG). Not PSI (pounds per square inch).
James
Not that I care....but an engine at idle produces a vacuum. Not pressure. So, any idle vacuum reading is just that (Vacuum being messured as Inches of Mercury (HG). Not PSI (pounds per square inch).
James
#16
Altitude affects the idle vacuum, too. With that, RPM, gauge accuracy, porting, mods, etc., I don't think it is very useful for comparing between cars. If you notice a distinct drop in idle vaccum, that might tell you something about your engine. Or if it starts jumping around a lot, that might tell you something as well. But comparing car to car doesn't tell you much, in my opinion.
-Max
-Max
#22
Lives on the Forum
480 to 510 mm Mercury from the Power FC Commander display @ 750 rpm idle. Converting to inches Mercury that's 19 to 20 inches Mercury. FWIW my Autometer shows 17 inches Mercury. I tend to believe the Power FC readout over the Autometer, at least for accuracy's sake.