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Fuel pressure?
I have a 90 GT with a b303, 70mmTB, 1.7's, pullies, cranefireball
I was wondering if an adjustable regulator would make my car run better? I always seem to have a miss at low rpm and sometimes it seems like i get a pop sound(lean?)out of the exhaust? With the mods i have i'm flowing alot more air than stock, so i think i need more fuel? Any advise? |
my car liked more fuel pressure
@ 42 lbs the car went 13.56 @ 44 lbs the car went 13.42 all with 19 lb injectors, you will just have to play with it one day at a track and see what your car likes ------------------ My slo aod- 3.73s, pullies, flowmasters, h-pipe, bbk cold air, and 13.42 in the 1/4 @ 103 mph |
Unless you're pushing 300 hp, which you aren't with just a cam, TB and pullies, fuel starvation isn't your problem.
Fuel starvation wouldn't be an issue at low RPMs, either. As far as running better with a different fuel pressure, it will only happen immediately after you bump it up or bump it down. After driving it for a while, the computer will recalculate its adjustment tables and compensate to go back to the computer controlled air/fuel ratios. I'm assuming that you still have stock heads and a stock intake? A 70mm TB is way to big and the cam is a mismatch. ------------------ 351W 89 Mustang GT Convertible |
jimberg..what is ur basis for that information??what u r basically saying is that no matter what pressure i set my car at the computer will learn this and go back to the stock settings???well i can say that is wrong at least on my cars and ones that ive worked on...my car with heads, intake, cams, exhaust 24#ers and 77mm mass air will not run at the stock FP no matter how many weeks i drive around at 38psi..my car will cut out up top and my plugs will be glazed...i have 24# injectors but i still need to bump up the FP to keep up with the incomming air..my car will run good at 42-45 psi depending on weather..now people running EGT gauges(serios tuners IE tropphy stock) and running 1340deg constant run after run..day after day, do they reset thier computer every day???and why make adj regualtors at all if the computer will reset it anyways??
i do agree that 70mm TB is too big also..i run one cuz A) i have at least 3.73's if not 4.10's in my rear at all times, and B) my cam although big makes increadible tourque and needs to breathe wll up top does the pop come when ur getting on it or when you are decelerating?? ------------------ 1987 black notch(ex 4 banger) DSS 306 w/ main support...Elderbrock 6028 heads..gt-40 intake..24# injectors...70 mm tb..77 pro-m...accel 300+..mac full legnth..tremec w/ pro5oh...full MAC exhaust,off road h-pipe,long tubes, catback...ron davis radiator..subframes, control arms...CFDF II..o yea holley FPR sucks..dont buy one.. AIM=onesillynotch |
LX XLR8R, the way you are using your FPR is correct. I have mine set at 47 psi for the same reason. The only effect setting it has is increasing or decreasing the amount of fuel available at the top end. The computer cannot control fuel pressure. That's strictly mechanical.
I was responding more to TheSloAod's message so I didn't cover all of the nuances of adjustable FPRs and how the computer works. I guess I'll go over it again. The computer has preprogrammed air/fuel settings that it sticks to. It uses the MAF and O2 sensors to keep it at those settings during closed loop operation (normal cruise). While it adjusts the amount of fuel delivered into the cylinders it keeps track of how long it's opening the injectors to keep the correct air/fuel ratio. This information is stored in adjustment tables and is used at WOT when the computer is just using MAF to figure out how much fuel to deliver. If you don't have fuel starvation problems, adjusting your FPR does nothing. That's why it's a waste to put it on a stock engine. If you're leaning out on the top end like you were, that means you have reached the throughput limits of your injectors running at stock pressure. By increasing the pressure, you are increasing the throughput limits of the injectors and, therefore, making it possible for the computer to do its job by delivering more fuel at WOT. Our computers are programmed to balance power with cleanliness. If cleanliness wasn't an issue, we would probably have a richer air/fuel mixture for more power. This is why TheSloAod saw positive results as he bumped up his fuel pressure at the track. The computer will see that fuel increase and start to adjust back down to the clean running air/fuel ratio. The next time he goes to the track it will be back to what it normally runs unless he resets the computer before his runs. If he was having fuel starvation problems, that's a different matter as explained above. I hope this is clearer now. ------------------ 351W 89 Mustang GT Convertible |
I motor will only suck(air) to it's capability.
It will suck the same amount of air with a 65mm TB as with a 70mm TB. A 70mm is less restrictive. It's like flowing a gallon of water through a 1 inch pipe vs. flowing a gallon of water through a 4 inch pipe. Less resistence You act like TB's are forced induction. |
It's not just as simple as opening up the breathing. If it were, why would runner length be such an issue? We would all have box intakes. By having too big of a throttle body, you are reducing your air velocity and, therefore, the momentum of the air moving into your plenum. With less momentum, you get less of a bounce in the runners, and less air being bounced into the cylinders. You do, by the way, get more into your cylinders than you would if you just let the cylinders suck air into them without an intake.
------------------ 351W 89 Mustang GT Convertible |
jimberg is right about the throttle body. If you don't have enough velocity you'll kill bottom end torque. Same idea as putting huge heads and open exhaust on a stock engine. It'll pull up top, but what happens to that snappy, torque? Its not there anymore, at least not as it used to be. 65mm is plenty for stock applications.
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70mm tb's dont show any improvement unless you are making over 400 hp N/A.
Jimberg- whats this about the computer using tables it has built at W.O.T? I thought open loop was all preprogrammed. And I have heads, intake, cam, etc...and my car runs much better on the lean side, like 35 psi. Dont know why you all run better richer? Maybe running a cooler water temp. has my computer trying to run it rich? I usually dont get over 180 degrees. ------------------ 1993 GT/AOD '93 Mustang GT |
oh well it seems to work fine on my ride and top end power is ten times better than stock.
you guys are right about the low end, it sure does slack in that department. And back to the regulator why do so many people use it if it doesn't do anything(ecu corrects for extra pressure)? |
Mach 1, Open loop just means that it isn't making adjustments based on feedback from O2 and other sensors. If you reset your computer and never run in closed loop mode, yes, it will run with preprogrammed settings. While it's in closed loop operation, however, the computer is determining the length of the injector pulses that go with the sensor signal feedback. It uses this information to build adjustment tables. These adjustment tables are then used at WOT to figure out how long to open the injectors to provide a fairly rich air/fuel ratio.
If your engine never gets warm enough, it will stay in open loop mode. That's why you should never get a thermostat below 180. Maybe that's why you see a difference with your pressure turned down. I find that hard to believe, though, since the leaner you run, the hotter the engine. Do you have a really good cooling setup? Aluminum radiator, water pump, etc.? As far as running richer for better performance, the SVO extender will go to a maximum air/fuel ratio of 14:1. That's still on the rich side. I read an article in one of my magazines that referred to that as a piston melting ratio. A some of the sample cars in that article were running best with 10:1 ratios which is very rich. Poopstang, this is where the benefit of adjustable FPRs is gained. If the amount of fuel being delivered by the computer is too much at WOT, then you drop the pressure so that the computer cannot deliver what it wants. Or, if your injectors can't deliver the amount of fuel that your engine needs, you can increase their overall capacity by bumping up the fuel pressure. I don't believe that you are in either situation so saving the money to buy something else is more beneficial. I hope you at least have a 77mm MAF sensor to go with that 70mm TB. ------------------ 351W 89 Mustang GT Convertible |
Yeah., my cooling set up rocks. Fluidyne rad., high flow water pump, hi flow 180 stat, I needed it because I was having problems with running hot. I have an AOD car with high stall converter, A/C, live in hot climate,etc... I try to keep it between 180 and 195. In the winter, it wont go to 180 though, but close.
I know what open loop and closed loop means, you dont have to repeat yourself. What I never heard of was that the WOT open loop tables were based on information built when the car was running in closed loop, and Im still not sure I believe it. Where did you get this information? ------------------ 1993 GT/AOD '93 Mustang GT |
Page 108 section 5 of Ford Fuel Injection and Electronic Engine Control covers adaptive strategy.
------------------ 351W 89 Mustang GT Convertible |
I know a pretty good mechanic who told my friends dad that i can trick my stock 5.0 computer to reprogram for more performance. He said to disconnect the battery, then reconnect it and start the car and immediately rev to about 2000 rpm. Anyone heard of this? Would this be possible with the entire stock fuel system?
------------------ 90 Mustang GT. K&N air filter, completely stock. Purchased at 107,000 for $3500 |
Some of you guys are running 302's with 24 lb injectors @ 47 psi?
Have any of you been dyno tuned with a wide band? I have aftermarket heads/cam/intake/etc... and made the best safe power at 35 psi. ------------------ 1988 Mustang GT 12.0 @ 122 1992 BadAzz Wrangler 1993 Explorer |
I have a 351W that I'm using 24# injectors at 47psi.
------------------ 351W 89 Mustang GT Convertible |
Jimberg - ill have to glance over the book when I have time, I have the book.
exgmguy - i agree with you, 35 psi rocks, and you proved it on a dyno.Of course , other combinations will be different, but a common mustang beginner mistake is to crank up the fuel pressure, thinking they are helping, but in reality, killing performance. ------------------ 1993 GT/AOD '93 Mustang GT |
so an adjustable regulator is no good for what i'm currently running?
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An FPR is not a good purchase at this point. It will be when you start making more power than your injectors can support.
19# injectors at 39psi can support about 270 hp at 90% duty cycle. This is based on .5 #s of fuel per horsepower per hour. Some engined do better and some do worse. .5 # is a good average. exgmguy, how did you go about tuning your fuel pressure on the dyno? Did you set your pressure, drive around for a few days and then go to the dyno, or did you set your pressure at the dyno between runs? ------------------ 351W 89 Mustang GT Convertible |
I think i'm at the 260-270 hp mark?
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I made fuel pressure changes between dyno runs.
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Anybody heard of C&L's new 76mm?any good?I'm thinking about getting one?need $
I'm starting to think my low end miss is my EGR valve? |
poopstang, I won't dispute what you're at, so if you think you're at your fuel limits, maybe an adjustable FPR will help. Your initial message, though, doesn't really fit with a fuel starvation issue. You'd be hitting your limits at high rpm, not low rpm.
Have you replaced your O2 sensors recently? If they're not working properly the computer could be incorrectly adjusting your air/fuel ratio. exgmguy, since you changed your fuel pressure between runs, it's a good bet that your computer has adapted by now. What more likely has happened is that the computer was adapting from run to run to get the most power. ------------------ 351W 89 Mustang GT Convertible |
I check the O2 heater's(turned on the key, felt them with my hands)they were warm, so i guess they work.
I can't seem to get any codes out of my car? I think the wire harness is f@#ked, the diagnostic lights in dash don't even work? Any advise on the EGR or the C&L 76mmMAF I'm go'n to take the vacuum line and harness off and see if it runs better at low rpm? Maybe i just need a gear? |
Taking the vacuum line off the EGR would be good to determine if there is a bad EGR vacuum control solenoid. If it doesn't make a difference, though, the EGR may still be stuck open. The only way to really test that is to remove it all together and bolt on a plate.
Crane recommended 3.55 gears for my E303. I'm sure you are probably in the same boat. Do you have a specific code reader or are you using jumpers? If one doesn't work, try the other. ------------------ 351W 89 Mustang GT Convertible |
i used a snap-on code reader and multimeter with jumpers, nothing works?
Any advise on a MAF? oh well my car is a pos!but she's fast so i'll keep her for now. |
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jimberg - based on the number of posts you've made, you've obviously been around a while, and your posts are intelligently written so you've obviously got some experience. It's just that your position on fuel pressure contradicts my own experience and the opinion of a significant percentage of this and many other message board members, as well as magazine articles and dyno shops. I know that my car put more HP to the ground dropping the fuel pressure to 33 PSI and it felt faster, and it still feels faster than when I had it tuned.
So I'll respectfully disagree with you for now. If I should get my hands on some information that convinces me otherwise (BTW I've got the book, I'll read that page first chance I get), I'll be the first to admit you were right. Until then... Chris |
Red82GT, no, since the computer has learned to drive on the street. Once you start doing WOT runs the computer will relearn to make peak power. It's kind of cool and kind of a pain. We'd all like to be able to lock in our best performance settings and tune it between runs. That's just not how it works.
withamc, as far as the page goes, it covers adaptive strategy. Mach 1 and I disagree as to whether or not adaptive strategy applies to open loop operation. We both agree that it does in closed loop. I'll try to point you at specific passages. Quote:
Quote:
This statement supports my response to Red82GT. It also clearly states that adaptive strategy even works during open loop mode. The computer doesn't simply revert to a bunch of hard coded tables at WOT. It uses different lookup tables, but they're still adapted to the base calibrations that are changed during closed loop and even open loop mode. There are other things that will change with fuel pressure that I really haven't mentioned in the past, but it's already difficult trying to get people to believe the stuff we've been discussing above. Let's say you have 30# injectors and are having trouble passing emissions (especially HC and CO). You should lower your fuel pressure down to a point that they perform like 24#ers (about 31psi). The reason you would do this is that the injectors have physical limits as to how fast they open and close. The bigger the injector, or higher the fuel pressure, the less control the computer will have at idle. When the computer attempts to open and close the injector at a faster rate than the injector can handle, it will simply meter more fuel than the computer wants, and, therefore, run rich at idle. Too low a pressure may actually affect the spray pattern. Like I've already said, I have my fuel pressure at 47psi because I am making more HP than the 24# injectors can support. I had definite fuel starvation problems at 39psi. Even at 45psi it seemed to lean out a little too much. 47 seems just right. The thing that hasn't really changed is my gas mileage. If I were to accept what you guys are saying, why wouldn't my gas mileage be significantly worse? Do you get better mileage at 33psi vs 39psi? Dyno shops probably don't tell people that tweaks of computer controlled cars are worthless because they want your business. Also, some of the older computers may not use adaptive strategies, or at least ones that are as strict. Didn't magazines start all the BS about adjusting the TPS to .999 volts? Our experiences, however, are different, aren't they (.94 to .98 is sufficient)? I suppose some will still swear by TPS adjustment still, but it's clear to me that if they can be wrong on the TPS they can be wrong on other things, too. I don't know if you guys can tell, but I really love these types of discussions. The most important thing that any of us can do that will help us make our cars go faster is by knowing how they work and what we can change to improve them. It will also save us from spending money on gimmicks. ------------------ 351W 89 Mustang GT Convertible |
Jimberg -While your logic is sound, and I read the book that you are referencing, the results seem to be different in real life.
How many people have drove to the strip, ran a few times, and thier e.t.'s improved, without touching the fuel pressure setting? Not many I would guess. Although the book states the theory, perhaps it just doesnt work as well as it is supossed too in actual conditions? Why is your computer not adapting? Are u saying your pressure is so high, that it runs good there, because your computer can not open your injectors any slower to compensate, or else it would? ------------------ 1993 GT/AOD '93 Mustang GT |
well, i personally see better times the more i run,,,,, (but that is probably more from lack of experience than anything!!!!) LOL
http://www.mustangworks.com/msgboard/wink.gif Q ------------------ Quin, 87 GT,306,forged/cut pistons,edelbrock head\intake,steeda#18cam,1.7rr,MSD Blaster tfi coil,A9L,pro-m75mm,24#inj,accufab65mm,2.5"pipes,hooker headers,dynomax exhaust,3.73 gr,110 lph fp,moroso cold air,ASP pullies, weld rims See my engine on user rides. I see your shwartz is as big as mine, now lets see how well you handle it! |
I have my fuel pressure set high since the computer can't open the fuel injectors long enough to provide the amount of fuel I need at WOT. Injectors must open and close so they cannot possibly run at 100% duty cycle. If they only can run at 90% duty cycle, and I think that number may be lower, that means that 24# injectors can only realisticly supply 21.6# of fuel in an hour at 39psi. That's enough for about 346hp( Assuming .5 #/hr/hp). By increasing pressure, more fuel can be delivered per injector pulse. At 47psi the injectors essentially become 29# injectors able to support about 417 hp at a 90% duty cycle.
As a side note, people have to make sure that their fuel pump goes with their injectors. A liter of fuel weighs about 1.5625#s. Multiply your pump capacity times that number and then divide by 8 to figure out what size injectors it'll support. As for improving after each fuel pressure tweak on the dyno or at the track, there's still the fact that the computer hasn't adapted yet. It may be that the O2 sensors are reporting a leaner condition that really exists and moving fuel pressure down compensates fot that for a while. Then the computer adapts again and you're back to running rich. I know this from experience. When I bumped up my pressure it ran a lot harder throughout the powerband. That power is gone now since it has adapted. ------------------ 351W 89 Mustang GT Convertible |
ok, after a little more thought, I think you are right and wrong at the same time. You say that you need an adjustable regulator because your injector size can not support your fuel needs at the factory 39 psi. This is correct and makes perfect sense. Crank the pressure, and you will get your increased fuel.
But why wont this also be beneficial to people with minor or moderate mods? I guess it comes down to defineing moderate and minor mods, horsepower numbers, etc..., but, if for example, a car needs 26 lph to run ats its best power, and they have 24 lph injectors at 39 psi, it wont perform its best. So, they slap on a adjustable regulator, crank it up a couple psi (the exact desired psi number is based on formulas, specific fuel comsumption, blah, blah, blah, etc...) to experiment, and the car performs better. Now, everythings cool, the car needs slightly more fuel for its particular combination, and now it has it, why would the computer even attempt to change anything? The car runs good, and maybe it is at the desired air/fuel ratio determined by the computer, so it has no need to revert back or change anything. Possibly the desired air/fuel ratio wasnt available with the factory computer programming, injector size and fuel pressure, but now it is. So, in essence, you are just "helping" the computer, not "tricking it" or "changing it", and it likes it, why would it try to change anything? ------------------ 1993 GT/AOD '93 Mustang GT |
I think we're almost on the same page. If you increase pressure, you increase the amount of fuel that the computer expects to deliver with a certain length pulse. The computer will see this as a rich condition and reduce the length of the pulse until it gets the air/fuel ratio it is programmed to keep. You still have the extra fuel you need at maximum load but the computer has adapted to the extra fuel that it doesn't need at lower load conditions.
------------------ 351W 89 Mustang GT Convertible |
Ok "JIMBERG" the only time I ever drive my car is at the strip. So does that mean that my cars computer is adjustd for WOT or what or is it different on a speed density system.
I have been afraid to do any mods to my car other than bolt ons cause I hear if you modify a speed density system it will run like sh!t. Someone on this board told me that I can just bump up my fuel pressure to compensate for mods is this correct in your opinion. ------------------ 88 mustang gt convertible bored to 306 BBk equal length headers mac cold air fender kit cowl hood nitto drag radials ford racing clutch flow masters h-pipe 160* thermostat 16 degrees of timing electric fan off 94' t-bird jacobs electronics cap and wires. best 60 ft 2.14, best 1/8th 9.65, best 1/4 15.2 @89mph |
I only have a mass air system and haven't done any research related to speed density systems. I've read stuff like you have that pretty much say that they are less adaptive to major modifications. If that's the case, maybe it's true about bumping up the fuel pressure. I can't really give you answer any more than that. Sorry.
Upgrading to mass air would probably be a good idea, though. ------------------ 351W 89 Mustang GT Convertible |
sorry, i just found this funny,,,
by JIMBERG "a liter of fuel weighs 'about' 1.5625 #'s" "ABOUT"???? I dont think you can get much more precise than tens of thousandths!!!!! lol Q ------------------ Quin, 87 GT,306,forged/cut pistons,edelbrock head\intake,steeda#18cam,1.7rr,MSD Blaster tfi coil,A9L,pro-m75mm,24#inj,accufab65mm,2.5"pipes,hooker headers,dynomax exhaust,3.73 gr,110 lph fp,moroso cold air,ASP pullies, weld rims See my engine on user rides. I see your shwartz is as big as mine, now lets see how well you handle it! |
Thanks for trying does anyone know how much $money$ the conversion from speed density to mass air will run me?
How much time can you knock off with a larger mas air sensor.? ------------------ 88 mustang gt convertible bored to 306 BBk equal length headers mac cold air fender kit cowl hood nitto drag radials ford racing clutch flow masters h-pipe 160* thermostat 16 degrees of timing electric fan off 94' t-bird jacobs electronics cap and wires. best 60 ft 2.14, best 1/8th 9.65, best 1/4 15.2 @89mph |
my costs for converting to mass air.
A9L~ 100$ Pro-m 75mm 150$ (used but basically new) wiring harness~ 30$ 24# injectors~ 225$ (optional) saudering kit~ 10$ (if you dont have one) thats all i can think of. cant tell you and specific #ers on performance gain from mass air meters. speed density is quicker for stock applications though, (you probably already know that) i think its more about matching your combo than specific meters and their dyno #ers. everyone seems to really like the pro-m77mm though. i might switch some day in the future to that one. good bit more expensive though. Q ------------------ Quin, 87 GT,306,forged/cut pistons,edelbrock head\intake,steeda#18cam,1.7rr,MSD Blaster tfi coil,A9L,pro-m75mm,24#inj,accufab65mm,2.5"pipes,hooker headers,dynomax exhaust,3.73 gr,110 lph fp,moroso cold air,ASP pullies, weld rims See my engine on user rides. I see your shwartz is as big as mine, now lets see how well you handle it! |
One thing that I haven't seen anyone mention, and I'm a little surpirsed, is that the lack of his low end torque and popping sound, might be caused by his Crane ignition not being setup properly. A very similar thing happened to me when my MSD box was installed. I would suggest checking your wiring for correct set up - your problem might be as simple as that!
------------------ '90 LX 5.0; 12K original miles (no sh*&); 3.55 gears; pulleys;Edelbrock Performer Heads; BBK shorties; MSD 6AL box w/ blaster 2 coil; Motorsport E303 cam; Pro-M 75mm MAF; BBK 70mm TB; Eibach spring kit; Southside welded subs; K&N cone filter charger; Hurst shifter; fiberglass turbo hood; A/C-less; rear seat-less; cat-less; 2 chamber Flos; Corbeau racing seats (fronts); 30# injectors; JMS Chip; 190 lb fp; TFS track heat Intake (12.299 @ 113) |
Quin, it's funny that you said that because I was thinking the same thing as a wrote it. http://www.mustangworks.com/msgboard/smile.gif I got that number somewhere on the web. It's probably a conversion from grams to lbs. I said "about" since all fuels have different weights.
I think if the ignition were set up improperly, the car would run poorly throughout the power band. When I first set mine up I forgot to hook up the retard line and it completely bogged at WOT. It's worth looking at, though. My own suspicion is that it is a mismatch of components. B303 cam with 1.7rr rockers stock heads and intake with 70mm TB and 76mm MAF. ------------------ 351W 89 Mustang GT Convertible |
My poping sound was there before i installed my ignition system
Can anyone tell which MAF to get 73mm or 76mm, whats the difference beside the size. why would i buy a 73mm when i could get a 76mm? Advise? |
I think what you have is correct for your throttle body. You need to get new heads and an intake to support the air flow as well as modify exhaust.
------------------ 351W 89 Mustang GT Convertible |
OK here are all my mods,
1 5/8 headers, off-road h-pipe, dynamax muffs, no-smog pump, no-A/C, pullies, b303, 1.7's, 70mmTB, ported upper and lower intake, shave heads(.020) and block(.020) |
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