Does the EEC adjust for bumped fuel pressure??

TEXSN95 · 05-12-2001, 12:40 PM

I've heard from some people that over time the EEC will adjust to bumping the fuel pressure. Is that true? The only way to do this would be to lower the injetor pulsewidth right? And it seems if that happened, you would get less atomization, less power, etc. Am I just blowin smoke???

------------------
Clint L.
White 95 Cobra #3637
58cc GT40X heads with mild porting, Crane 2031 cam, FRPP 65 TB, 1.7s, Cobra intake, homeade cold air, 155lph, pullies, Tokico Illuminas, C springs, GW LCAs, Kenny Brown super subs, Steeda CC plates, aluminum driveshaft, Steeda quadrant, B&M ripper, Kirban FPR, MSD6A, Taylor wires, Mac shorties, off road hpipe, 2 1/2 ultra flows w/ dumps, R hood, Euro clear corners, stock 3.08s
13.61 @ 104.7 w/ 2.22

toms89 · 05-12-2001, 01:01 PM

Yes the computer will compensate for what ever fuel pressure adjustments you make. It will adjust over time according to what it reads from the O2 sensors. Higher fuel pressure will cause the computer to shorten pulse width over time. Its more of a track tuning trick....works ok for short term, computer doesnt have time to compensate. Has to run in closed loop for period of time before computer can make adjustments.

jimberg · 05-12-2001, 01:04 PM

Nope. The EEC does adjust for the fuel pressure by doing exactly what you say, but I wouldn't say you get less power. Even at WOT, it uses adjustment tables that are built when at cruise. It's not a long time, either, that it takes to adjust.

You can get two advantages from adjusting your fuel pressure. The first is when your injectors aren't able to deliver enough fuel for the amount of air you're getting into the cylinders. Say you only have 24# injectors but you need 28# of fuel to meet your fuel requirements. Since the throughput ratings are based on 39psi, you can turn your pressure up to compensate. Just take your target output (28) and divide it by your current output (24) and then take that result and multiply it by 39. Set fuel pressure to 45.5 psi and you basically have 28# injectors.

You may also feel that the computer is running too rich at WOT. You can prevent this by cutting back on the pressure some to prevent the computer from being able to provide too much fuel. This is a little more questionable since the computer may protect the engine and start limiting power. I don't think that happens, though, since some people seem to get an improvement when they do it.

The only way to get away from the factory set air/fuel settings is with a chip, the SVO extender, or something like the Speedbrain.

------------------
351W 89 Mustang GT Convertible

TEXSN95 · 05-13-2001, 05:56 PM

I know it runs better now after I bumped it from 38 to 44. So theoretically, resetting your computer before your track runs *might* make it run a bit better..maybe like a 1/10 or so?

------------------
Clint L.
White 95 Cobra #3637
58cc GT40X heads with mild porting, Crane 2031 cam, FRPP 65 TB, 1.7s, Cobra intake, homeade cold air, 155lph, pullies, Tokico Illuminas, C springs, GW LCAs, Kenny Brown super subs, Steeda CC plates, aluminum driveshaft, Steeda quadrant, B&M ripper, Kirban FPR, MSD6A, Taylor wires, Mac shorties, off road hpipe, 2 1/2 ultra flows w/ dumps, R hood, Euro clear corners, stock 3.08s
13.61 @ 104.7 w/ 2.22

jimberg · 05-13-2001, 08:19 PM

I neglected to mention that part of it. One way that you can actually get use out of a fuel pressure change is to go to a dyno or track where you can do a lot of runs. Reset your computer and keep tweaking the pressure until you get the results you want. When you drive it around town, the EEC will adjust, but the next time you go to the track all you have to do is reset the computer again.

Running a richer throughout the powerband will definitely help you run better. It should get your more than a tenth, too. When I bumped my fuel pressure up to 45, I could definitely feel the difference. After a while, though, it settled back to normal. I wasn't starving for fuel, anymore, though.

I want to get a speedbrain or an SVO extender when I can afford one.

------------------
351W 89 Mustang GT Convertible

05-12-2001, 12:40 PM	#1
TEXSN95 Registered Member Join Date: Mar 2001 Location: college station, tx Posts: 143	Does the EEC adjust for bumped fuel pressure?? I've heard from some people that over time the EEC will adjust to bumping the fuel pressure. Is that true? The only way to do this would be to lower the injetor pulsewidth right? And it seems if that happened, you would get less atomization, less power, etc. Am I just blowin smoke??? ------------------ Clint L. White 95 Cobra #3637 58cc GT40X heads with mild porting, Crane 2031 cam, FRPP 65 TB, 1.7s, Cobra intake, homeade cold air, 155lph, pullies, Tokico Illuminas, C springs, GW LCAs, Kenny Brown super subs, Steeda CC plates, aluminum driveshaft, Steeda quadrant, B&M ripper, Kirban FPR, MSD6A, Taylor wires, Mac shorties, off road hpipe, 2 1/2 ultra flows w/ dumps, R hood, Euro clear corners, stock 3.08s 13.61 @ 104.7 w/ 2.22

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05-12-2001, 01:01 PM	#2
toms89 Registered Member Join Date: Jul 2000 Location: Eldersburg, MD Posts: 182	Yes the computer will compensate for what ever fuel pressure adjustments you make. It will adjust over time according to what it reads from the O2 sensors. Higher fuel pressure will cause the computer to shorten pulse width over time. Its more of a track tuning trick....works ok for short term, computer doesnt have time to compensate. Has to run in closed loop for period of time before computer can make adjustments.

05-12-2001, 01:04 PM	#3
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	Nope. The EEC does adjust for the fuel pressure by doing exactly what you say, but I wouldn't say you get less power. Even at WOT, it uses adjustment tables that are built when at cruise. It's not a long time, either, that it takes to adjust. You can get two advantages from adjusting your fuel pressure. The first is when your injectors aren't able to deliver enough fuel for the amount of air you're getting into the cylinders. Say you only have 24# injectors but you need 28# of fuel to meet your fuel requirements. Since the throughput ratings are based on 39psi, you can turn your pressure up to compensate. Just take your target output (28) and divide it by your current output (24) and then take that result and multiply it by 39. Set fuel pressure to 45.5 psi and you basically have 28# injectors. You may also feel that the computer is running too rich at WOT. You can prevent this by cutting back on the pressure some to prevent the computer from being able to provide too much fuel. This is a little more questionable since the computer may protect the engine and start limiting power. I don't think that happens, though, since some people seem to get an improvement when they do it. The only way to get away from the factory set air/fuel settings is with a chip, the SVO extender, or something like the Speedbrain. ------------------ 351W 89 Mustang GT Convertible

05-13-2001, 05:56 PM	#4
TEXSN95 Registered Member Join Date: Mar 2001 Location: college station, tx Posts: 143	I know it runs better now after I bumped it from 38 to 44. So theoretically, resetting your computer before your track runs might make it run a bit better..maybe like a 1/10 or so? ------------------ Clint L. White 95 Cobra #3637 58cc GT40X heads with mild porting, Crane 2031 cam, FRPP 65 TB, 1.7s, Cobra intake, homeade cold air, 155lph, pullies, Tokico Illuminas, C springs, GW LCAs, Kenny Brown super subs, Steeda CC plates, aluminum driveshaft, Steeda quadrant, B&M ripper, Kirban FPR, MSD6A, Taylor wires, Mac shorties, off road hpipe, 2 1/2 ultra flows w/ dumps, R hood, Euro clear corners, stock 3.08s 13.61 @ 104.7 w/ 2.22

05-13-2001, 08:19 PM	#5
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	I neglected to mention that part of it. One way that you can actually get use out of a fuel pressure change is to go to a dyno or track where you can do a lot of runs. Reset your computer and keep tweaking the pressure until you get the results you want. When you drive it around town, the EEC will adjust, but the next time you go to the track all you have to do is reset the computer again. Running a richer throughout the powerband will definitely help you run better. It should get your more than a tenth, too. When I bumped my fuel pressure up to 45, I could definitely feel the difference. After a while, though, it settled back to normal. I wasn't starving for fuel, anymore, though. I want to get a speedbrain or an SVO extender when I can afford one. ------------------ 351W 89 Mustang GT Convertible