Fuel Pressure

moponys · 08-19-2002, 11:09 AM

I was getting crappy times with my fuel pressure set at 48psi.

Can you guys take a look at my sig. and tell me what it should be set at...

I have now set it to 38psi.

Thanks...

PKRWUD · 08-19-2002, 12:11 PM

Not sure why you have 24# injectors. 38 psi is probably fine. You are the only one who can tell. Make adjustments until it runs it's best, and leave it there.

Take care,
~Chris

moponys · 08-19-2002, 12:15 PM

Do you think the 24# injectors are too small or do you think the stock 19#r's would would have been just fine???

Dark_5.0 · 08-19-2002, 12:32 PM

You would still be well within the 19 # injectors range, but the 24 # injectors are a good choice for you set up. @48psi you were running way rich at WOT.......38psi sounds about right to me.

With all the money you have in your ride you would greatly benifit from a dyno tune. Thats my advice.

Later,

PKRWUD · 08-19-2002, 12:35 PM

19# injectors are plenty for up to 350 hp in a N/A engine, and from your sig, you don't have 350 hp.

Take care,
~Chris

moponys · 08-19-2002, 12:40 PM

Thanks for the advice...

I blew a tire out the other day and will be replacing it today...

I can't wait to see if setting the pressure at 38 makes a big difference.

You know about the Dyno tuning, I agree 100% but I'm so lame, the closest Dyno is about 75 miles away and I'm too lazy to make an appointment to get it done but I'm gonna try soon or at least before I go back to the track.

Thanks again...

eatsgmcar · 08-19-2002, 01:06 PM

For you information, i have edelbrock perf RPM head
with E303 cam and the weak cobra intake. My fuel
pressure is at 38 PSI with #30 injectors. I did the fastest
quarter mile at that pressure.

When i had the # 24 injector the car was faster when
the FPR was at its maximum (65-70 PSI).

I think the optimum gas pressure vary a lot from car to
car. The difference could come from different mass air,
computer, compression etc I m just guessing correct me if
i am wrong.

SC

moponys · 08-19-2002, 01:14 PM

I think you're right... It probably does vary from car to car.

I know that in the past when I had set my pressure to 42, the car seemed slower but I don't if it was just my mind messing with me.

From the info I've gathered from other cars with the somewhat the same mods as mine, I'm hoping that around 38psi will help my sorry ets dramatically.

thanks...

eatsgmcar · 08-19-2002, 01:25 PM

My ET went from 13.30 @ 102 to 12.43 @ 108
when i raised up my fuel pressure from 38 psi to 67
psi with 2 psi increment each time. (# 24 injectors)

When it was at 38 psi i could heard a lot of small "pop"
coming out of the pipes as i was slowing down at the
end of the track. The car was also very inconsistent and
ran better when the engine was hot. I lost 2 thenth at
night compare to what the car did during the day. I think
that it was few symptoms telling me that my car was hungry.

Hope this help,

SC

moponys · 08-19-2002, 01:31 PM

It does help Thanks...

My idle is kinda ruff with the cam I have and when I set the psi to 38, it sounded alot smoother...

I don't know if that tells you anything or not...

I'll start playing with it tonight as you did by increasing it by two until it feels right starting at 38psi.

eatsgmcar · 08-19-2002, 02:02 PM

I am guessing again, but when the fuel pressure is
varying suddently when adjusting it, the idle could
be a little more rough until the computer recalculate
its A/F ratio table. You should ask this to someone
that has more experience but i could be right.

The idle has nothing to do with the perfomance at
WOT. I would go to the track to adjust everything
or have a dyno session.

SC

SlowGT · 08-19-2002, 02:41 PM

Tried to put my $.02 in earlier but my computer crashed. Our setups are very similar. I'm running 21# accel injectors @ 37.5#. I could've got by with 19# but since I was buying new I figured I'd allow the extra margin for improvements. What condition are your injectors? new, used, leaking by? Planning on a dyno run in October with wideband O2. If you want, I could let you know how it turns out with my A/F ratio.

Saw a supercharged 91 on a chassis dyno last week gain 31 ftlb & 17 hp (AT the wheels) just by reducing fuel flow. He didn't have an adjustable regulator and he could only do so much with his FMU. 1st run his A/F ratio went off the scale low (super rich) as soon as they put the pedal down. 2nd run his A/F ratio held where it should for an extra 1200rpm then it slammed off the scale low. 3rd run...I didn't hang around to see since he couldn't make any other adjustments. If you don't have a dyno, then you just have to play the test & tune game.

Check out Accel's site at www.mrgasket.com , they've got some pretty technical info on their injectors. Maybe it'll help you figure out which direction to go.

moponys · 08-19-2002, 02:45 PM

Cool thanks for the info...

Yeah if you could let me know how your session goes, that would be helpful. I will have hopefully figured it out by then...

I'm gonna try to get some dyno runs in by then too.

Thanks

Dark_5.0 · 08-19-2002, 04:11 PM

Quote:

Originally posted by eatsgmcar
For you information, i have edelbrock perf RPM head
with E303 cam and the weak cobra intake. My fuel
pressure is at 38 PSI with #30 injectors. I did the fastest
quarter mile at that pressure.

When i had the # 24 injector the car was faster when
the FPR was at its maximum (65-70 PSI).

I think the optimum gas pressure vary a lot from car to
car. The difference could come from different mass air,
computer, compression etc I m just guessing correct me if
i am wrong.

SC

Sorry dude but either you fuel pressure gauge is messed up. Or you are making 500 HP. with just heads and a cam.

24# injectors @65-70 psi would be way in the HELL too much fuel.

This goes further than this being my opinion. Logicaly, realisticly or any other way you want to look at it there is no way.

eatsgmcar · 08-20-2002, 10:05 AM

DARK_5.0

The car is faster at that pressure. It is anormally
high but i have no way to see what are the signals of the
Sensors and what the computer does with it. I know it
looks like the cars has 500 HP when looking at the pressure
and injectors, however with the computer s reading and
treatment it could only shoot for 350 hp-400hp of gas.

I know an other 5.0 which has a similar pressure and his set
up looks like mine. I think the mass air or the higher compression
could be the problem. Anyway, i have never seen any black smoke
at the pipe (maybe a little smoke when i shift it) and the car is
very consistent at the track.

If anyone could help me with this or tell me what could be the problem
feel free to leave your comments.

_______________________________________________

BEST 0-60 FEET 1.633 sec
BEST 1/8 MILE 7.820 sec
BEST MPH 88.41 MPH
BEST 1/4 MILE 12.283 sec
BEST MPH 108.95 MPH

Dark_5.0 · 08-20-2002, 11:31 AM

I cant argue with your results

........

Nice times,

Hyper92GT · 08-20-2002, 12:39 PM

This is an interesting thread. The topic has been covered quite a bit in the past, but it is one that seems to elude everyone.
I too am running 19lb injectors, with heads/cam/intake car. The analyzer says i too should have FP at 67psi, currently and dynoed with 38psi (roughly 300rwhp) untuned and with no adj on the dyno.
I am going to the track this weekend and will post results at 67psi.
Best to date is 13.45@110mph with 2.1 60'.
Any logic to such high fuel pressure????? Any damage??
thanks

eatsgmcar · 08-20-2002, 12:59 PM

When the pressure was at 38 psi (# 24 injectors) the
car was very slow. When i was flooring at 2000 RPM
i could notice a kind of flute noise in the pipes like if
the explosion has never occur in a cylinder.

Also, as i said, i could easely notice a lot of "pop"
when releasing the gas pedal at the end of the 1/4 mile.

Now the car is running fine with 38 psi and #30 injectors.
The spark plugs are fine, no black smoke, never broke, good ET,
no strange noise only strange fuel set up.

Is there someone who can explain that?

SC

By the way,Hyper92GT i still have my #24 injector and vortech
MAF tube......... interested? HEHEHE

Hyper92GT · 08-20-2002, 01:06 PM

Did you really pick up 6mph with just a FP change,
nothing, absolutely nothing else. Let me know.

I am S/C the car over the winter, so if you have 36lbs I'll buy those

Again anyone explain.

SlowGT · 08-20-2002, 01:13 PM

Quote:

Best to date is 13.45@110mph with 2.1 60'

What kind of tires were you running for that pass?? With that 60' & MPH, I'm guessing you had daily driver street tires. Please prove me right.

Thanks.

08-19-2002, 11:09 AM	#1
moponys Registered Member Join Date: May 2001 Location: Antioch, CA 94521 Posts: 181	Fuel Pressure I was getting crappy times with my fuel pressure set at 48psi. Can you guys take a look at my sig. and tell me what it should be set at... I have now set it to 38psi. Thanks... __________________ N/A 94 GT vert w/aode...12.19 @110 w1.67 60' Some bolt ons

08-19-2002, 12:32 PM	#4
Dark_5.0 Registered Member Join Date: Apr 2001 Location: Staging lane Posts: 4,337	You would still be well within the 19 # injectors range, but the 24 # injectors are a good choice for you set up. @48psi you were running way rich at WOT.......38psi sounds about right to me. With all the money you have in your ride you would greatly benifit from a dyno tune. Thats my advice. Later, __________________ 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

08-19-2002, 12:35 PM	#5
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	19# injectors are plenty for up to 350 hp in a N/A engine, and from your sig, you don't have 350 hp. Take care, ~Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

08-19-2002, 12:40 PM	#6
moponys Registered Member Join Date: May 2001 Location: Antioch, CA 94521 Posts: 181	Thanks for the advice... I blew a tire out the other day and will be replacing it today... I can't wait to see if setting the pressure at 38 makes a big difference. You know about the Dyno tuning, I agree 100% but I'm so lame, the closest Dyno is about 75 miles away and I'm too lazy to make an appointment to get it done but I'm gonna try soon or at least before I go back to the track. Thanks again... __________________ N/A 94 GT vert w/aode...12.19 @110 w1.67 60' Some bolt ons

08-19-2002, 01:14 PM	#8
moponys Registered Member Join Date: May 2001 Location: Antioch, CA 94521 Posts: 181	I think you're right... It probably does vary from car to car. I know that in the past when I had set my pressure to 42, the car seemed slower but I don't if it was just my mind messing with me. From the info I've gathered from other cars with the somewhat the same mods as mine, I'm hoping that around 38psi will help my sorry ets dramatically. thanks... __________________ N/A 94 GT vert w/aode...12.19 @110 w1.67 60' Some bolt ons

08-19-2002, 12:11 PM	#2
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Not sure why you have 24# injectors. 38 psi is probably fine. You are the only one who can tell. Make adjustments until it runs it's best, and leave it there. Take care, ~Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

08-19-2002, 12:15 PM	#3
moponys Registered Member Join Date: May 2001 Location: Antioch, CA 94521 Posts: 181	Do you think the 24# injectors are too small or do you think the stock 19#r's would would have been just fine??? __________________ N/A 94 GT vert w/aode...12.19 @110 w1.67 60' Some bolt ons

08-19-2002, 01:06 PM	#7
eatsgmcar Registered Member Join Date: Jul 2002 Location: Pont Rouge, Quebec, Canada Posts: 45	For you information, i have edelbrock perf RPM head with E303 cam and the weak cobra intake. My fuel pressure is at 38 PSI with #30 injectors. I did the fastest quarter mile at that pressure. When i had the # 24 injector the car was faster when the FPR was at its maximum (65-70 PSI). I think the optimum gas pressure vary a lot from car to car. The difference could come from different mass air, computer, compression etc I m just guessing correct me if i am wrong. SC

08-19-2002, 01:25 PM	#9
eatsgmcar Registered Member Join Date: Jul 2002 Location: Pont Rouge, Quebec, Canada Posts: 45	My ET went from 13.30 @ 102 to 12.43 @ 108 when i raised up my fuel pressure from 38 psi to 67 psi with 2 psi increment each time. (# 24 injectors) When it was at 38 psi i could heard a lot of small "pop" coming out of the pipes as i was slowing down at the end of the track. The car was also very inconsistent and ran better when the engine was hot. I lost 2 thenth at night compare to what the car did during the day. I think that it was few symptoms telling me that my car was hungry. Hope this help, SC Last edited by eatsgmcar; 08-19-2002 at 01:35 PM..

08-19-2002, 01:31 PM	#10
moponys Registered Member Join Date: May 2001 Location: Antioch, CA 94521 Posts: 181	It does help Thanks... My idle is kinda ruff with the cam I have and when I set the psi to 38, it sounded alot smoother... I don't know if that tells you anything or not... I'll start playing with it tonight as you did by increasing it by two until it feels right starting at 38psi. __________________ N/A 94 GT vert w/aode...12.19 @110 w1.67 60' Some bolt ons

08-19-2002, 02:02 PM	#11
eatsgmcar Registered Member Join Date: Jul 2002 Location: Pont Rouge, Quebec, Canada Posts: 45	I am guessing again, but when the fuel pressure is varying suddently when adjusting it, the idle could be a little more rough until the computer recalculate its A/F ratio table. You should ask this to someone that has more experience but i could be right. The idle has nothing to do with the perfomance at WOT. I would go to the track to adjust everything or have a dyno session. SC

08-19-2002, 02:41 PM	#12
SlowGT Registered Member Join Date: Jun 1999 Location: Columbia Co, PA Posts: 303	Tried to put my $.02 in earlier but my computer crashed. Our setups are very similar. I'm running 21# accel injectors @ 37.5#. I could've got by with 19# but since I was buying new I figured I'd allow the extra margin for improvements. What condition are your injectors? new, used, leaking by? Planning on a dyno run in October with wideband O2. If you want, I could let you know how it turns out with my A/F ratio. Saw a supercharged 91 on a chassis dyno last week gain 31 ftlb & 17 hp (AT the wheels) just by reducing fuel flow. He didn't have an adjustable regulator and he could only do so much with his FMU. 1st run his A/F ratio went off the scale low (super rich) as soon as they put the pedal down. 2nd run his A/F ratio held where it should for an extra 1200rpm then it slammed off the scale low. 3rd run...I didn't hang around to see since he couldn't make any other adjustments. If you don't have a dyno, then you just have to play the test & tune game. Check out Accel's site at www.mrgasket.com , they've got some pretty technical info on their injectors. Maybe it'll help you figure out which direction to go. __________________ Old Slow GT New Slow GT--> under construction Latest Addition: 95 Cobra R, #73, bone stock, ~6100 miles.

08-19-2002, 02:45 PM	#13
moponys Registered Member Join Date: May 2001 Location: Antioch, CA 94521 Posts: 181	Cool thanks for the info... Yeah if you could let me know how your session goes, that would be helpful. I will have hopefully figured it out by then... I'm gonna try to get some dyno runs in by then too. Thanks __________________ N/A 94 GT vert w/aode...12.19 @110 w1.67 60' Some bolt ons

08-20-2002, 10:05 AM	#15
eatsgmcar Registered Member Join Date: Jul 2002 Location: Pont Rouge, Quebec, Canada Posts: 45	DARK_5.0 The car is faster at that pressure. It is anormally high but i have no way to see what are the signals of the Sensors and what the computer does with it. I know it looks like the cars has 500 HP when looking at the pressure and injectors, however with the computer s reading and treatment it could only shoot for 350 hp-400hp of gas. I know an other 5.0 which has a similar pressure and his set up looks like mine. I think the mass air or the higher compression could be the problem. Anyway, i have never seen any black smoke at the pipe (maybe a little smoke when i shift it) and the car is very consistent at the track. If anyone could help me with this or tell me what could be the problem feel free to leave your comments. _______________________________________________ BEST 0-60 FEET 1.633 sec BEST 1/8 MILE 7.820 sec BEST MPH 88.41 MPH BEST 1/4 MILE 12.283 sec BEST MPH 108.95 MPH Last edited by eatsgmcar; 08-20-2002 at 10:14 AM..

08-20-2002, 11:31 AM	#16
Dark_5.0 Registered Member Join Date: Apr 2001 Location: Staging lane Posts: 4,337	I cant argue with your results ........ Nice times, __________________ 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

08-20-2002, 12:39 PM	#17
Hyper92GT slow like mud Join Date: Mar 2000 Location: toronto Posts: 180	This is an interesting thread. The topic has been covered quite a bit in the past, but it is one that seems to elude everyone. I too am running 19lb injectors, with heads/cam/intake car. The analyzer says i too should have FP at 67psi, currently and dynoed with 38psi (roughly 300rwhp) untuned and with no adj on the dyno. I am going to the track this weekend and will post results at 67psi. Best to date is 13.45@110mph with 2.1 60'. Any logic to such high fuel pressure????? Any damage?? thanks __________________ 1992 DECH GT Not stock, still slow.

08-20-2002, 12:59 PM	#18
eatsgmcar Registered Member Join Date: Jul 2002 Location: Pont Rouge, Quebec, Canada Posts: 45	When the pressure was at 38 psi (# 24 injectors) the car was very slow. When i was flooring at 2000 RPM i could notice a kind of flute noise in the pipes like if the explosion has never occur in a cylinder. Also, as i said, i could easely notice a lot of "pop" when releasing the gas pedal at the end of the 1/4 mile. Now the car is running fine with 38 psi and #30 injectors. The spark plugs are fine, no black smoke, never broke, good ET, no strange noise only strange fuel set up. Is there someone who can explain that? SC By the way,Hyper92GT i still have my #24 injector and vortech MAF tube......... interested? HEHEHE

08-20-2002, 01:06 PM	#19
Hyper92GT slow like mud Join Date: Mar 2000 Location: toronto Posts: 180	Did you really pick up 6mph with just a FP change, nothing, absolutely nothing else. Let me know. I am S/C the car over the winter, so if you have 36lbs I'll buy those Again anyone explain. __________________ 1992 DECH GT Not stock, still slow.

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