Have an adjustable FPR and wanted to know if anyone has done some homework on the best fuel pressure to run? I read that stock is 58psi and I have mine sitting at about 63psi. Don't know if i will gain anyhting by being higher than that?
I'm not sure what kind of N/A mods you have (nothing in your registry), but without substantially increased airflow, you won't gain anything by raising the pressure like that - if anything you might lose a little bit of power by running too rich. Now, if you have all the bolt on mods, you might want to raise the fuel pressure a bit, although here again, unless you have an all out setup, the stock computer and fuel system will probably correct for it. I'd think you'd be better off with HPT to tune for it and tweak fuel and timing rather than just fiddling with a FPR...
whiteboyz24 wrote:Have an adjustable FPR and wanted to know if anyone has done some homework on the best fuel pressure to run? I read that stock is 58psi and I have mine sitting at about 63psi. Don't know if i will gain anything by being higher than that?
If you have a LD9 it should be around 40 PSI. You HAVE nothing filled out in your profile so no one knows what engine you have. Also do you have a
wideband, and if you do not.
STOP PLAYING WITH THE FUEL PRESSURE.
PRND321 Till I DIE
Old Motor: 160whp & 152ft/lbs, 1/4 Mile 15.4 @88.2
M45 + LD9 + 4T40-E, GO GO GO
Yeah alot of people did some homework on the best fuel pressure to run. Infact the same people did homework on the best injectors to use and even the best sensors to determine how much fuel is needed. They were all GM engineers who then programed the pcm accordingly.
It does not matter what you have done to your increase air unless you have put on a turbo or supercharger. I highly doubt that you have since you are you are asking a ? like this. I don't know because you have not even filled out your profile. Until you you fill out your profile just stay stay in the newbies forum.
FORGET GIRLS GONE WILD WE HAVE GOVERNMENT SPENDING GONE WILD!
Wade.....I know enough that if i did have boost i would be using and FMU and not an AFPR. so until i fill out my profile:
venom intake manifold
short ram
58 mm TB
venom fuel rail
msd fuel pump
UR crank pulley
removed a/c
venom 400
rk sport 4:1 headers
magnaflow cat back
b&m shift kit
Ive read other threads about the HPT on N/A cars. some say it wont do much until you get into cams or hi compression. wiht the mods I have does anyone think i need it?
I dont have a wideband but ive had it on a scanner and the A/F is fine. I got the 58psi from a helm's manual.
What motor do you have??? If you have a 2.4/LD9 your fuel pressure is too high. The Venom intake manifold and Venom 400 were waste of money. Truly the fuel rail was as well for your mods. Looking at the scanner to see air/fuel is the same as making fuel adjustments without a wideband. My 2.4 runs rich with stock fuel pressure and stock injectors.
As for what HPT can do on a N/A set-up well truly I only know of one person to truly find out. They gained 6-8 who across the power band on a bone stock Ecotec. That is pretty good, because most of your mods you have won't get you that.
FU Tuning
Your best bet would be hp tuners. If you got that you would not need an fmu or afpr if you go boosted.
Edited 3 time(s). Last edited Monday, July 02, 2007 7:39 PM
FORGET GIRLS GONE WILD WE HAVE GOVERNMENT SPENDING GONE WILD!
I e-mailed rk-sport about this a while back, who tracked down the engineer that originaly designed their afpr for our cars. They claimed a 6hp gain with only an intake and exhaust. After talking with the engineer I found out they did the original dyno test and proved 62psi to be the best fuel pressure. I am running an aeromotive afpr on an ecotec with only all the bolt-ons, and I don't regret it one bit. I have an 05 ecu so really I only get power gains when I am at around wot, all other times the ecu adjusts pulse width anyway, fuel pressure is not as big a factor.
theres really no BEST fuel pressure to run. it will be different from place to place (elevation will be a factor, as well as mods, and engine condition). but you will have to do some dyno tuning to find out what what works best with your setup. i;ve done a decent amount of research on this from our cars to various other makes and models i;ve been interested in.... all have pointed to that answer in all honesty.
Thanks for the input.
I knew someone would say something about the venom 400. I read alot of people saying it does nothing at all, maybe it doesnt for their car...maybe they have a bone stock car?? All i know is that I lost about 3/4 sec in the quarter mile after installing it.
whiteboyz24 wrote:Thanks for the input.
I knew someone would say something about the venom 400. I read alot of people saying it does nothing at all, maybe it doesnt for their car...maybe they have a bone stock car?? All i know is that I lost about 3/4 sec in the quarter mile after installing it.
The only reason I say something about it is no one with it has been able to run close to my times. I also say the same about the HO intake manifold. All the people running them, but yet most N/A J's are still in the 15's. Why?
FU Tuning
David Arestie wrote:I e-mailed rk-sport about this a while back, who tracked down the engineer that originaly designed their afpr for our cars. They claimed a 6hp gain with only an intake and exhaust. After talking with the engineer I found out they did the original dyno test and proved 62psi to be the best fuel pressure. I am running an aeromotive afpr on an ecotec with only all the bolt-ons, and I don't regret it one bit. I have an 05 ecu so really I only get power gains when I am at around wot, all other times the ecu adjusts pulse width anyway, fuel pressure is not as big a factor.
I can guarantee you that isn't on a stock tune (at least not for an LD9). Higher fuel pressure allows greater atomization of the fuel, which results in a more complete burn of the fuel. IIRC if you go too high, you run a higher risk of reaching the fuel's flashpoint before the valves close.
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"Youth in Asia"...I don't see anything wrong with that.
Again... I'd love to see dyno numbers proving the Venom intake manifold is a 'waste' of money.
Until then, maybe... "The Venom intake manifold IS bigger than stock, but no one really knows if it gains anything at all." would be a correct form of replacement wording.
Brian Whalen wrote:David Arestie wrote:I e-mailed rk-sport about this a while back, who tracked down the engineer that originaly designed their afpr for our cars. They claimed a 6hp gain with only an intake and exhaust. After talking with the engineer I found out they did the original dyno test and proved 62psi to be the best fuel pressure. I am running an aeromotive afpr on an ecotec with only all the bolt-ons, and I don't regret it one bit. I have an 05 ecu so really I only get power gains when I am at around wot, all other times the ecu adjusts pulse width anyway, fuel pressure is not as big a factor.
I can guarantee you that isn't on a stock tune (at least not for an LD9). Higher fuel pressure allows greater atomization of the fuel, which results in a more complete burn of the fuel. IIRC if you go too high, you run a higher risk of reaching the fuel's flashpoint before the valves close.
Your right, It was on an ecotec but it was a stock tune. I agree with you on everything you said, I just was trying to prove that even an n/a car can benefit from an afpr, a lot of people seem to disagree. The only real way to figure out the best fuel pressure is the Dyno.
Does anyone know of a place w/ a dyno around Fort Myers , FL ?? just moved here and dont know anyone.
David Arestie wrote:I have an 05 ecu so really I only get power gains when I am at around wot, all other times the ecu adjusts pulse width anyway, fuel pressure is not as big a factor.
Correction, you have an 05 ECU, so you are ALWAYS running in closed-loop, and raising you're fuel pressure a little won't make a difference at any TP.
whiteboyz24 wrote:I knew someone would say something about the venom 400. I read alot of people saying it does nothing at all, maybe it doesnt for their car...maybe they have a bone stock car?? All i know is that I lost about 3/4 sec in the quarter mile after installing it.
If you saw a gain, then it was due to weather conditions, or track prep, or your driving. Nothing about the "Venom 400" will "remap the fuel curves" in the ECU as they claim. Have you read the reviews on these things? They are by people who have complementary mods such as "electric supercharger" and "intake temp sensor resistor"...give me a break.
whiteboyz24 wrote:Does anyone know of a place w/ a dyno around Fort Myers , FL ?? just moved here and dont know anyone.
Have you thought about maybe checking the regional forums, that's what they are there for afterall.
fortune cookie say: better a delay than a disaster
On the same day? it has an on off switch and it was more than just 1 run. And I have an auto which is consistant. I never read anything that says it remaps the fuel curve.
A. it tells the computer the air is more dense via the map sensor
B. makes sure there is proper voltage to the TPS for WOT
I'm sure that its not beneficial to every application.
i didnt know about the regional; forums....thanks
whiteboyz24 wrote:I never read anything that says it remaps the fuel curve.
A. it tells the computer the air is more dense via the map sensor
B. makes sure there is proper voltage to the TPS for WOT
Their sales pitch includes the phrase "remapping" about a dozen times.
A. Did you know our ECU does not use the MAP sensor to control fuel?
B. If you are WOT, and you are not getting full voltage, wouldn't a functional TPS be a better (and cheaper) investment?
fortune cookie say: better a delay than a disaster
Well I've played with the fuel pressure and actually got better driveability with less fuel pressure than more.
There was no big gain or anything like that but did enjoy better driveability with lower pressure.
The stock fuel pressure was at about 43psi and dropped it to about 32 psi.
With the readings I was getting on the short and long fuel trims, decided that I'd keep it at 35 psi and have been happy with it ever since.
I've noticed less black, sooty deposits also on the tailpipe with less fuel pressure.
Track times remained the same since power enrichment mode kicks in but even there, the car felt really good and a bit stronger.
But hey, what's a feeling if it's not dyno proven.
Hope this information helps a bit.
Misnblu.com
Newbie member since 1999
Thank you Dave and JBO! 
go as high as your fuel pump can take but not much beyond stock regulation, the benefit of higher fuel pressure is better atomization better power and greater efficiency however if too much pressure it can damage your injectors theres a happy medium you have to find
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
Rodimus Prime wrote:go as high as your fuel pump can take but not much beyond stock regulation, the benefit of higher fuel pressure is better atomization better power and greater efficiency however if too much pressure it can damage your injectors theres a happy medium you have to find
The problem is, when I tried just that, the driveability of the car decreased.
More sputtering at idle, and more hesitation upon quick throttle blips got me to decrease my fuel pressure over stock psi.
Also, with the information I've read from tuners all over, they'll tell you that our cars run rich, and reducing the pressure will get you closer to stoich.
More stoich will usually mean more power but there's a fine line on how much fuel to remove.
Last, when you go wot, the power enrichment mode kicks in so there should always be enough fuel to keep the a/f good enough to keep it from knocking.
With my fuel trims, knock gauge that I have from my scan gauge, can datalog these parameters for evaluation on just driving around town or taking it to the track.
I've got some more tweaking to do once I change out the O2 sensor with a heated unit.
Hopefully that'll change things a bit.
Misnblu.com
Newbie member since 1999
Thank you Dave and JBO!
Misnblu wrote:More stoich will usually mean more power
Stoich does not equal best power. Best power comes around 13.9, whereas stoich is around 14.7
fortune cookie say: better a delay than a disaster
^^^^Correct
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"Youth in Asia"...I don't see anything wrong with that.
whiteboyz24 wrote:Thanks for the input.
I knew someone would say something about the venom 400. I read alot of people saying it does nothing at all, maybe it doesnt for their car...maybe they have a bone stock car?? All i know is that I lost about 3/4 sec in the quarter mile after installing it.
the venom 400 doesn't do anything. All it does is trick your car's ecu into thinking your pushing the gas more.. but guess what, 100% throttle is still 100%. so instead of using the Venom400, try pushing your gas down a little further.
I garauntee the lost time is because of driver ability, nothing more.
hpt will help slightly on an intake/exhaust car but will really help if you have cams.
and just fyi, the minute you start tuning your air/fuel ratio your injectors are too small. before screwing with fuel pressure, think about upgrading your injectors first. I'm still running without an AFPR, however it is on the to-do list.
already tried running injectors. venom injectors that are supposed to be only 10% above stock. car runs fine but the computer throws a code because its compensatng too much......so no... i dont need injectors until i do internal work
and you cant push the gas further than all the way. all i have to do is show up at a drag strip and then prove that it helped me in the 1/4 mile......and posting slips is not proof to me.
