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Benefit of disconnecting vacuum hoes from FPR?

1002 Views 11 Replies 6 Participants Last post by  speed51133
Benefit of disconnecting vacuum hose from FPR?

As it says, I drover a '98 GTI with the vac. hose capped off at the FPR and at the conection port on the plenum. What is the benefit of this? Opinions?


[Modified by Cabdriver, 11:26 PM 11-24-2001]
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Re: Benefit of disconnecting vacuum hose from FPR? (Cabdriver)

Ya the benefit is,,,,,,,, Don't do it.
Re: Benefit of disconnecting vacuum hose from FPR? (Cabdriver)

i agree, don't do it... not really any benifit, except that you may run too rich at high vac.
Fuel injection kinda relies on some kind of manifold pressure sensing... motronic blindly relies on a 'differential' FPR that adjusts fuel pressure so that it is exactly 3 bars (or 4) above manifold pressure.
There are better ways to increase your fuel flow, like use the FPR the way it should be used, and use bigger injectors, or use a 4 bar FPR instead of a 3bar, etc.
Re: Benefit of disconnecting vacuum hose from FPR? (queue)

RUNNING RICH AT HIGH VAC IS BAD RUNNING RICH AT HIGH RPM'S IS GOOD
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Re: Benefit of disconnecting vacuum hose from FPR? (queue)

IF IT IS EXACTLY SO MANY BARS ABOVE MANIFOLD PRESSURE THAT MEANS IT WOULD BE 3 OR 4 AT WIDE OPEN THROTTLE, THERE IS NO PRESSURE AT WIDE OPEN AND THERE IS 12 POUNDS AT HALF THROTTLE. I WORK FOR VW
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Re: Benefit of disconnecting vacuum hose from FPR? (KDoggsPimpJetta)

That's right!!!!!!!! Don't disconnect it!
But you don't have to disconnect the vaccum hose!
There is no vaccum in the hose when full throttle postion, so there is the same situation as disconnect the hose!
quote:[HR][/HR]RUNNING RICH AT HIGH VAC IS BAD RUNNING RICH AT HIGH RPM'S IS GOOD
[HR][/HR]​
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Re: Benefit of disconnecting vacuum hose from FPR? (monkey28)

ill throw inmy 2 cents,
dont disconnect it!!!
there is ZERO bennefit to disconect it.
Re: Benefit of disconnecting vacuum hose from FPR? (KDoggsPimpJetta)

quote:[HR][/HR]IF IT IS EXACTLY SO MANY BARS ABOVE MANIFOLD PRESSURE THAT MEANS IT WOULD BE 3 OR 4 AT WIDE OPEN THROTTLE, THERE IS NO PRESSURE AT WIDE OPEN AND THERE IS 12 POUNDS AT HALF THROTTLE. I WORK FOR VW
[HR][/HR]​
Whoa, calm down there buddy.
You are confusing me. you say 0 pressure at WOT and 12 psi at half-throttle.
WTF? Are you talking fuel or manifold pres.?
You couldn't be talking about fuel pressure because you shoulnd't ever have 0 fuel pressure,
and you couldn't be talking about manifold pressure, because as long as you are still NA you will never have positive manifold pressure.
So what the hell are you talking about 12psi at half-throttle?
WHAT? AM I A F-CKING IDOT?



[Modified by queue, 2:40 AM 11-27-2001]
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Re: Benefit of disconnecting vacuum hose from FPR? (queue)

No, he is using wrong measuring unit, is 12"Hg, not 12 psi!!! It can tell you when you installed a vaccum gauge.
And there is no manifold pressure on NA cars, he means is manifold VACCUM
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Re: Benefit of disconnecting vacuum hose from FPR? (monkey28)

quote:[HR][/HR]No, he is using wrong measuring unit, is 12"Hg, not 12 psi!!! It can tell you when you installed a vaccum gauge.
And there is no manifold pressure on NA cars, he means is manifold VACCUM
[HR][/HR]​
I know, just that if he 'works for vw' you think that he would get his units right.
Plus, the fuel pressure SHOULD be 3 bars at WOT (with the 3bar FPR, and relative to ambient pres.) and it should be LESS THAN 3 bars at part throttle, and MORE THAN 3 bars under boost (for us F/I people). That is to say, a 3 bar FPR will hold the fuel pressure 3bars ABOVE manifold pressure, not ambient pressure. So what I said is correct, I feel that he doesn't know the difference between 1 bar, 1 atmosphere, 1 psi, and 1 inch of mercury.
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Re: Benefit of disconnecting vacuum hose from FPR? (queue)

i know its confusing, i was a t first.
this is the deal....
a 3 bar fuel pressure regulator, makes 3 bar of pressure in your fuel system ONLY when the intake manifold is at atmospheric pressure(WOT). when you are in vaccume(part throttle or idle), the fuel pressure gauge would read LESS than 3 bar. If you were in boost, it would read more than 3 bar.
basically how the fuel pressure reg works, is it makes sure there is always 3 bar of pressure difference between your manifold, and the atmosphere. since you can change you manifold pressure via the throttle, the regulator has to know that this is happening. thats why it has the vaccume port on it that should be hooked up. if you did not hook it up, you would run rich at idle, and lean at WOT.
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Re: Benefit of disconnecting vacuum hose from FPR? (speed51133)

oh, but i dont work for VW!!!
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