fuel pressure

superwillard · 07-22-2003, 04:43 PM

This year I added 1.7 rocker arms. I was wondering if I need to turn up the fuel pressure from my set up last year I was running 50 psi with the line off. I might go to the track this weekend so I thought I would ask.

Thanks for any info

Dark_5.0 · 07-22-2003, 04:49 PM

No, there is no need to turn up your fuel pressure your car has to be running hella rich as it is.

I am only runnng 43 psi of fuel pressure WOT.

When you say with the line off are you saying that you are not running a vacuum line on you regulator?

superwillard · 07-22-2003, 04:57 PM

The plug look real nice at the track but yes it does run rich on the street at that pressure I turn it down when I drove home I'll just try aroud there. That was with the vacum line off. I was thinking that if the engine is taking more air in I would need more fuel. This is with 19lb injectors

Ackbar00 · 07-22-2003, 05:13 PM

Quote:

Originally posted by Dark_5.0
No, there is no need to turn up your fuel pressure your car has to be running hella rich as it is.

I am only runnng 43 psi of fuel pressure WOT.

When you say with the line off are you saying that you are not running a vacuum line on you regulator?

Not if he has 19#'rs still. I run between 48-51 depending on weather.

I read and set mine with the line off than reconnect it when done.

Nixon1 · 07-22-2003, 10:11 PM

Dont mean to hijack this post..just a quick question. What does pulling the vacuum line off do to your fuel pressure reading? I checked mine a while back at idle with the line connected and got 38-40. Does it go up with the vacuum disconnected?

TMASTER · 07-23-2003, 12:42 AM

run 41 psi with vacuum off, with your setup.

PKRWUD · 07-23-2003, 05:51 AM

Quote:

Originally posted by Nixon1
Dont mean to hijack this post..just a quick question. What does pulling the vacuum line off do to your fuel pressure reading? I checked mine a while back at idle with the line connected and got 38-40. Does it go up with the vacuum disconnected?

The engine requires more fuel at WOT, so the engineers had to figure out a way of adding fuel then, but in a way that would not effect emissions, drivability, and economy at other times. The answer was to make the spring that moves the diaphram inside the regulator a little bit stronger, so that uncontrolled, the fuel pressure would be higher than normal, to satisfy the needs at WOT. They then attached a vacuum port to the back side of the diaphram, so that when there was engine vacuum, it would slightly overpower some of the spring tension, reducing the fuel pressure. Since the manifold vacuum drops as the throttle opens, this was the perfect answer. At idle, when the pressure should be the lowest, there is full manifold vacuum at the regulator, so the pressure is at it's lowest. As the throttle opens, the manifold vacuum drops, and the spring overpowers the vacuum, opening the diaphram more and more, until finally, at WOT, when there is little to no manifold vacuum, the spring has opened to it's fullest, giving you it's maximum fuel pressure. Since an engines vacuum at idle can vary, but it is always zero at first when you go to WOT, fuel pressure is usually checked with the vacuum line disconnected, representing WOT.

Get it?

Take care,
~Chris

Dark_5.0 · 07-23-2003, 08:46 AM

Quote:

Originally posted by Ackbar00
Not if he has 19#'rs still. I run between 48-51 depending on weather.

I read and set mine with the line off than reconnect it when done.

Come on man you are running mid 12's and he is running a 14 flat your car makes 300 RWHP so 50 psi sounds right for your car but not his.

07-22-2003, 04:43 PM	#1
superwillard Registered Member Join Date: Feb 2003 Location: roseville mi. Posts: 26	fuel pressure This year I added 1.7 rocker arms. I was wondering if I need to turn up the fuel pressure from my set up last year I was running 50 psi with the line off. I might go to the track this weekend so I thought I would ask. Thanks for any info __________________ 86 hatch 5 speed 3.73 gears gt40p heads,gt 40 intake,headers 70 mm tb 195 lph pump off road h-pipe 2.5 exhaust this year rear air bag electric fan 1.7 rockers no sway bar Best et 14.09 last year 60 ft 1.98

07-22-2003, 04:49 PM	#2
Dark_5.0 Registered Member Join Date: Apr 2001 Location: Staging lane Posts: 4,337	No, there is no need to turn up your fuel pressure your car has to be running hella rich as it is. I am only runnng 43 psi of fuel pressure WOT. When you say with the line off are you saying that you are not running a vacuum line on you regulator? __________________ 92' LX-Big brakes, Lots and lots of suspension, GT40X heads, Ported cobra intake, stock cam, Vortech SC trim. 00' Lightning-Stock 88'CRX-13 second ego killer

07-22-2003, 04:57 PM	#3
superwillard Registered Member Join Date: Feb 2003 Location: roseville mi. Posts: 26	The plug look real nice at the track but yes it does run rich on the street at that pressure I turn it down when I drove home I'll just try aroud there. That was with the vacum line off. I was thinking that if the engine is taking more air in I would need more fuel. This is with 19lb injectors __________________ 86 hatch 5 speed 3.73 gears gt40p heads,gt 40 intake,headers 70 mm tb 195 lph pump off road h-pipe 2.5 exhaust this year rear air bag electric fan 1.7 rockers no sway bar Best et 14.09 last year 60 ft 1.98

07-22-2003, 10:11 PM	#5
Nixon1 Registered Member Join Date: Jan 2003 Location: Palm Bay, FL Posts: 432	Dont mean to hijack this post..just a quick question. What does pulling the vacuum line off do to your fuel pressure reading? I checked mine a while back at idle with the line connected and got 38-40. Does it go up with the vacuum disconnected? __________________ '91 Mustang GT 5.0 AOD Daily Driver Current stats: NEW 302 short block, E-303 cam (@.050, 220/220, .498/.498, 110 degrees), 1.6 roller rockers, Performer RPM heads (aluminum, 1.9/1.6, 60cc chambers), Cobra intake, Granatelli 75mm MAF, Billet AFPR, Equal-Length Shorty Headers, Off-Road X Pipe, Flowmasters, 4.10 POSI 13.73 at 103.8, ~2.2 60'

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07-23-2003, 12:42 AM	#6
TMASTER Registered Member Join Date: Sep 2002 Location: TEXAS Posts: 161	run 41 psi with vacuum off, with your setup.