TII Boost Guage at Idle
#1
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TII Boost Guage at Idle
when my car is idling (or trying to at least), what should the boost guage read? 0 or -20? everywhere i drive it says -20 until i step on the gas, then it jumps to 0 then starts moving up... i keep wanting to think it's supposed to be at 0 and that i have a vacuum leak, but then again, i don't know, thanks
#2
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the lower the Neg level at idle the better.
-20 is prolly off a bit, stock gauge sucks, but ya thats normal, and good.
Robert
-20 is prolly off a bit, stock gauge sucks, but ya thats normal, and good.
Robert
Last edited by Rpeck; 05-30-03 at 04:09 PM.
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Yup.. the more vac at idle, the better. The closer to 0 you get at idle, the lower your compression. -20 lbs is like a new engine if its a true reading. I get -12 to -14 lbs at a 750 idle on my guessometer guage
Think of your engine as if it was you sucking on a straw.. Without boost, you have vacuum because its sucking in air.
Think of your engine as if it was you sucking on a straw.. Without boost, you have vacuum because its sucking in air.
#6
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Gauges read in different scales, look on your gauge and use math to compare. Here is the standard which I'm pretty sure about, almost positive, but off the top of my head.
29.92" Hg=80cm Hg=1 Bar=14.7psi
29.92" Hg=80cm Hg=1 Bar=14.7psi
#7
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Wait a minute you get -.5 bar? I better check for vacuum leaks or something. That would be around 7psi and I'm getting around 11" Hg which would be.......5.5psi about. But of course its a Guessometer so I'll check it with the vac gauge and see how accurate it is at vacuum. I will get better Autometer is just for now. Will probably dump the lightshow gauge for a EGT also. Maybe not, I dunno.
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Net wisdom is that you should see at least 14" of vacuum at a 750rpm idle on FC stock ports. Ported motors will have lower idle readings and if your idle is lower than 750 it will also read lower. Watch the units as well - the stock gauge is in mm Hg * 10. -20 -> -200 mm Hg which is about 6" vacuum (IIRC). At idle the stock gauge should always be pegged at -20.
At a 750rpm idle I get about 15-16" vacuum. When idling at 600rpm it drops to about 12-13". This is on a stock TII with 150k. If your seeing less, look for vacuum leaks and test your compression.
Henrik
87TII
BTW. -20# is physically impossible.
At a 750rpm idle I get about 15-16" vacuum. When idling at 600rpm it drops to about 12-13". This is on a stock TII with 150k. If your seeing less, look for vacuum leaks and test your compression.
Henrik
87TII
BTW. -20# is physically impossible.
#11
I'm a boost creep...
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Re: TII Boost Guage at Idle
Originally posted by jasonw3579
everywhere i drive it says -20 until i step on the gas, then it jumps to 0 then starts moving up...
everywhere i drive it says -20 until i step on the gas, then it jumps to 0 then starts moving up...
The first thing you should do if you plan to modify your car is buy a proper aftermarket boost gauge. That will give you a much more complete and accurate picture of what your engine's doing.
Last edited by NZConvertible; 06-01-03 at 06:39 AM.
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Will a free flow intake and exhaust cause less vacuum at idle? I may have some vac leaks somewhere too, ordering the good hose as soon as I pick a color, cheap stuff is just that.
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