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Old 07-03-2001, 11:21 AM   #1
adeck
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Default S-AFC, positive intake maniford pressure?

When I open the throttle up the intake pressure on my safc reads zero and stays there untill I let off the throttle. I know that there is some positive pressure but it will not read it. Is it possible the the factory sensor cannot read positive pressure?
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Old 07-03-2001, 11:41 AM   #2
JGard
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would it maybe be reading the vacuum pressure? cause that would then be correct...
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Old 07-03-2001, 11:49 AM   #3
adeck
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Yes that is what it reads but there is no vaccum at wot, at wot there should be + intake pressure with my homemade *ramair*.
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Old 07-03-2001, 12:01 PM   #4
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just the opposite, I would think...

if air is being sucked into the engine, it is defenitely creating a vacuum behind it. check out the hoses that go into the air box... those count on air being sucked out of them. the more the engine pulls, the more it creates a vacuum there.

but, I could be wrong....
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Old 07-03-2001, 12:06 PM   #5
adeck
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The more open the throttle is the more equal the pressure would be between the inside and outside of the TB. The less you are on the throttle the harder it is for the motor to suck air in. That's my opinion. What I am trying to find out is if my homemade *ram-air* is actually forcing air in!
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Old 07-03-2001, 01:11 PM   #6
tmat3
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I thought that the only way to make that gauge bring to the + side is to get a turbo or Supercharger. I don't see any way to bring that gauge to + w/o it because the engine has to create a vacuum and it cannot create more pressure than the outside world (1 atm = 1012hpa) w/o forced induction (boost).
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Old 07-03-2001, 01:20 PM   #7
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yeah, I don't think you're "ramair" is all that forceful...
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Old 07-03-2001, 01:33 PM   #8
adeck
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Can you explain why the safc is reading zero when the throttle is open? I think the safc would display + numbers but the factory sensor in the intake cannot read positive numbers.
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Old 07-03-2001, 01:44 PM   #9
MY99 2.5GT
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What does your SAFC measure vaccum pressure in? PSI? Maybe it is lower than 1Psi and the SAFC doesn't display less than whole numbers.

Just a wild guess.
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Old 07-03-2001, 01:47 PM   #10
adeck
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It measure is mmHG, I have acctually got a +0.01 on the safc.
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Old 07-03-2001, 02:26 PM   #11
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? anyone ?
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Old 07-03-2001, 02:47 PM   #12
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My votes go with:

Quote:
Originally posted by tmat3
I thought that the only way to make that gauge bring to the + side is to get a turbo or Supercharger. I don't see any way to bring that gauge to + w/o it because the engine has to create a vacuum and it cannot create more pressure than the outside world (1 atm = 1012hpa) w/o forced induction (boost).
and:

Quote:
Originally posted by JGard18
yeah, I don't think you're "ramair" is all that forceful...
-WaC
Wayne
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Old 07-03-2001, 02:56 PM   #13
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dammit, I am gonna prove this. I am not saying this *ram-air* is forcing a lb of boost or something, I am just saying that there is positive pressure in the intake, it may be small, but it is greater than equal pressure.
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Old 07-03-2001, 02:58 PM   #14
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dude, wayne knows what he's talking about. I'd leave it be.
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Old 07-03-2001, 03:02 PM   #15
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Listen, I know what I am talking about there is positive air pressure.
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Old 07-03-2001, 03:55 PM   #16
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If you insist, prove it, then come back and let us know what speed you had to get the car up to to start noticing a ram-air effect.
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Old 07-03-2001, 04:01 PM   #17
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exactly....please prove that all this air will be "forced" into the intake, without forced induction, ie. a turbo
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Old 07-03-2001, 04:10 PM   #18
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I believe the stock MAP sensor will read positive pressure up to 2 psi.
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Old 07-03-2001, 04:27 PM   #19
adeck
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I need a gauge that will measure in +. It seems like the stock sensor doesn't measure +, but it has read +0.01 on the SAFC at about 35 MPH 3rd gear.
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Old 07-03-2001, 04:29 PM   #20
adeck
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I need a gauge that will measure in +. It seems like the stock sensor doesn't measure +, but it has read +0.01 on the SAFC at about 35 MPH 3rd gear. If anybody lives near me I will be happy to show you?
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Old 07-03-2001, 04:33 PM   #21
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Don't get me wrong, I'm not bashing you or anything, but I would not consider a +.01 reading with an S-AFC and the stock MAP sensor an accurate reading.
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Old 07-03-2001, 04:38 PM   #22
adeck
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I agree, so what do you want me to do install a boost gauge?
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Old 07-03-2001, 04:59 PM   #23
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i think the "ram air" doesn't create enough pressure at freeway speeds to make a difference
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Old 07-03-2001, 05:07 PM   #24
adeck
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OK listen, picture a 2.5 in a wind tunnel. What the car is doing is cutting a hole in the air so, the air that is forced up the hood is being caught by the hood scoop. With my intake "all air comming through the scoop is being guided into the throttle body through a rounded sheet metal box."
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Old 07-03-2001, 05:17 PM   #25
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but it's not like that air is compressed at all. also, is it an air-tight seal from the outside of the hood scoop to your intake? i doubt it.

there's plenty of room for air to leak out. And like I said, it's A: not compressed air, and B: not forced. it more or less "finds" it's way to the intake.
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