Tech tip
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Racer
Joined: Dec 2009
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From: Reno NV
Le Mans Master
Joined: Jul 2007
Posts: 5,043
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From: Tampa Florida
I would think that running a higher fuel rail pressure would only "show" a difference running at WOT. At different throttle positions other than WOT - I believe the computer would attempt to correct the enrichment by reducing the injector's "flow"
Le Mans Master
Joined: May 1999
Posts: 6,513
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From: Windermere FL
I have an adjustable pressure regulator, and I gave up playing with it and just set it to the stock 43 lbs. If you want to dump in more fuel you have to play with the ECM programming.
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Drifting
Joined: Sep 2002
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From: Suwanee,Ga
I have just gone through the fuel process because of a issue with gas in my plenum, and the FSM says the vacuum line is to INCREASE fuel pressure with load?
So how can no vacuum on the same pump pressure do anything?
TJM
Le Mans Master
Joined: Jan 2003
Posts: 5,858
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From: Santa Maria CA
I would see a slight MPG gain of at max 1 MPG when it was disconnected and capped off. I do remember testing with and without on the same stretch of freeway back to back under same driving conditions, speeds, etc. I would drive a certain amount of freeway miles using the trip meter, stop, pop the hood open, plug it back in, and drive back the same road and distance. I felt no noticeable difference in performance, certaintly no "serious" change in acceleration. My coolant temps where unaffected.
Last edited by 86PACER; Jan 20, 2010 at 03:26 PM.
Team Owner
Joined: Jan 2003
Posts: 20,293
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From: Summerland B.C. Canada
It will raise you idle and cruise pressure to the same pressure you would see under WOT or high load. The ECM will adjust when in closed loop. It will not make it higher than the reg is set for.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
What Agent 86 said.
It's bogus. When you got to WOT (and have no vacuum in the intake) you end up w/the same fuel pressure anyway. You DON'T get better gas mileage. The display may show a better reading but that's b/c the ECM doesn't know about the mechanical change that's been made. If you did your gas mileage using long devision after a fill up, I'm sure that you'd find that this "mod" decreased your actual fuel milage.
Waste of time.
It's bogus. When you got to WOT (and have no vacuum in the intake) you end up w/the same fuel pressure anyway. You DON'T get better gas mileage. The display may show a better reading but that's b/c the ECM doesn't know about the mechanical change that's been made. If you did your gas mileage using long devision after a fill up, I'm sure that you'd find that this "mod" decreased your actual fuel milage.
Waste of time.
Race Director
Joined: Sep 2003
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From: Database Error Indiana
Former Vendor
Joined: Nov 2006
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From: Carmichael ca
I heard about this years ago, 20? The theory was that the increase in pressure would change the injector spray by better atomizing the fuel. I have no idea if that's BS or not. I doubt the story's claim are accurate. I can't imagine you'd see that much difference unless the higher pressure was compensating for some other issue.