increase fuel pressure in your fuel rail

[Protoss]

I was talking to Macklum, and has anyone done a mod like this??

take the vaccum line off of the FPR, and plug the like so that the intake is "sealed" again. you will see 41psi(?) in your fuel rail. then advance the timming at the disty 4 or 5 degrees.

[MazdaRacer]

go ahead, then tell us how it went

ya don't smoke do ya? :p:

[Protoss]

not around my car, in my car, or near the hood.

spark... spark.... BOOM. no good

i'm going to dyno my car whn i find $75 to do so. then when i do the FPR and disty i'll post what happnened

[Tai Mai Shu]

do you mean taking the tube off the vaccuum solenoid and then sealing the hole? what are you gonna do with the tube?

[zenilder]

the only problem with this is that if you do that, the FPR is going to be closed at idle. Have an idea what might happen?

Well, when you are putting 41psi into the fuel line/fuel rail, but there is no where for it to go, with the exception of the fuel injectors, and it is idling, fuel tends to find other means of escape. Namely from around the fuel injectors. If you want to have your engine catch fire while driving, go ahead and do it.

Even if the fuel pressure would hold, what's the point? You'll only be making the engine run rich. There's no power in a rich fuel mixture. If you had a turbo, it might help, but not much. You would still have fuel leak even if you had a turbo.

Our cars prolly run around a 11.something or upper 10 fuel ratio with the stock computer. Stick 41 psi in the fuel rail, and you'll prolly run even richer around 9.something. Stumble stumble?
An ideal fuel ratio is 12.5 (for best power) while accelerating and 14.7 (for better emissions) while idling/coasting. You won't even get near that with 41psi in an NA engine. You'd be better off putting a piggyback computer on to tune the fuel than just stuffing the fuel rail.

To give you an idea of what I'm talking about, check this out. When they publish the mag, I'm going to build it for my truck. GEH it's a frickin' fuel hog!

Later.

[cortez]

You are basically making the regulator think you are at full throttle all the time. So really, you are adding more gas at part throttle and idle, where the ECU and O2 sensor will try to compensate anyway, but it won't make a difference at full throttle.

[macklum]

I ran my 92 like this for 3 years ,I never had a problem . Milage was better ,throttle responce was better . The only draw back was ,sometimes it was hard to start ,took a few extra cranks to get the car going ,I also ran one heat range colder plugs . When I sold the car ,it didn't burn any oil ,and the compression was even across all 4 cyl's .

[zenilder]

Okay. How exactly does that work? I fail to see the logic in that.

"I just raised my fuel pressure to 41 psi. I now am putting more fuel into the engine at all RPMs. Now I'm getting better mileage."

Maybe I'm missing something?

[Kevin]

*gets out the bag of marshmelllows, hershey bars and grahm crackers*

come on dude, hurry up, i'm gettin hungry
peace

[Protoss]

you will be running richer, but that is why you would advance your timming at the disty. i think it would be a waste of time to explain this concidering you are already prejudgist to such a thing.

[cortez]

Dude, what you did only raises the fuel pressure to the level that it would otherwise normally go when you floor it. The only difference is that you have more pressure when you are going at less than full throttle.

It does not change anything that happens when you floor the car, which is, I assume, what you would do if you wanted to get max power out of the motor (floor it).

So, lets say that you had set your ignition timing so that it's just less than what would make it ping at full throttle. Now, you added more timing because you have more fuel at part throttle, but since it didn't change anything at full throttle, you will now get ping at full throttle.

In any case, these cars run pretty rich already at full throttle, so they really don't need any extra fuel unless you have a built motor.

[Protoss]

Originally posted by cortez
Dude, what you did only raises the fuel pressure to the level that it would otherwise normally go when you floor it. The only difference is that you have more pressure when you are going at less than full throttle.

It does not change anything that happens when you floor the car, which is, I assume, what you would do if you wanted to get max power out of the motor (floor it).

So, lets say that you had set your ignition timing so that it's just less than what would make it ping at full throttle. Now, you added more timing because you have more fuel at part throttle, but since it didn't change anything at full throttle, you will now get ping at full throttle.

In any case, these cars run pretty rich already at full throttle, so they really don't need any extra fuel unless you have a built motor.

WTF do you mean by "built" and do you have any idea what you are talking about??

ok think about this, our injector run on a "period variable" control. so at WOT the injectors are open for say 10milliseconds. at other it varies from 4 to 9 milisec.

now what does that have to do with fuel pressure?

well the FPR is just a diaphram (as stated before) that will react to the pressure differencese between the 2 sides. os if you suck on one side the diaphram will buldge towards lesser pressure. basic ****, everything wants to be at equlimbium.

Actually the FPR does NOT see only a WOT. this is because the intake mani is sub-atm. Proven because air moves through it. hello potential difference, the only reason things move. The FPR is just taken out of the equasion, by making it a constant.

Your ECU still controlls ****. and your fuel pump still pumps. and the O2 sensor still tells the computer the post chamber mixture. BUT you do need to advance the disty this allows for the flame to properly propagate. that is the important part! 5 degrees is enought time to burn that extra fuel.

just doing the FPR thing is a waste, but if you do a timming advance you do get a gain.

as for at idle.... i dont see how that would happen. pressure is presure, be it dynamic or static... it is force per unit area.

[cortez]

When you floor the car, you have ZERO vac. in the manifold and ZERO vac. on the line that goes to the FPR. When you plug that line, you are making the FPR behave like the car is floored. Do you agree with me so far? If not, start by getting a turbo gauge or any vacuum gauge and hook it up to the FPR vac. line. With the throttle plate open, the pressure inside the plenum is the same as the pressure outside the plenum. Open system. Basic physics.


All I am telling you is that once you floor the car, your mod will not make any difference at all. Absolutely zero. Your mod makes the fuel pressure regulator behave like the car is at Wide Open Throttle all the time. So in terms of all out power, it does not make a difference.

Whatever performance gain you get from advancing the timing is a gain you can get already without touching the FPR. The mod will not allow you to add any more timing than you already could add without the mod.

The ECU does not use the O2 sensor when you floor the car. It uses its maps and that's it. If you run an adjustable fuel pressure regulator that allows you to adjust the pressure at full throttle, then you'll be adding more fuel when you floor the car.

I am also telling you that unless you have a lot of work done to your motor, (what a "built motor means") like ported head, cams, header, exhaust, intake, large VAF, you know a lot of improvements to the air flow through the motor, your motor is already running fairly rich with the factory settings, so it does not need any extra fuel.

So, you can choose to believe me or not, but I do know what I am talking about. I am not trying to bash you or anything. I'm just sharing what I have learned myself after having worked on more BP motors than I care to remember.

[Protoss]

Originally posted by cortez
[B]When you floor the car, you have ZERO vac. in the manifold and ZERO vac. on the line that goes to the FPR. When you plug that line, you are making the FPR behave like the car is floored. Do you agree with me so far? If not, start by getting a turbo gauge or any vacuum gauge and hook it up to the FPR vac. line. With the throttle plate open, the pressure inside the plenum is the same as the pressure outside the plenum. Open system. Basic physics.

You want to talk physics?? lets dance! ok at WOT you do not have 0 vaccum if you did you would not have any air moving through it. see the attached


if you do have air moving through an open system or a control volume, you have a velocity. in you ahve a velocity you have a difference in pressures and thus you have a releitive vaccum which will be LOWER than the ambient.

ok i am agreeing with you that you are making the car act differently. but it will not act in the exact same way as WOT. this is where i disagree. as i have stated over and over again, the disty has tob e advanced. i know just advancing the distributor you do see a gain, but with this you see more of a gain, that i what i am out to prove

also the FPR is seeing a different pressure on the vaccumline side than what is is used to. the intake mani is always sub ambient. it has to be physics dictates so. by leaving that open to ambient you changing the geometry of how your fuel rail works.

All I am telling you is that once you floor the car, your mod will not make any difference at all. Absolutely zero. Your mod makes the fuel pressure regulator behave like the car is at Wide Open Throttle all the time. So in terms of all out power, it does not make a difference.

you sound like a broken record...

Whatever performance gain you get from advancing the timing is a gain you can get already without touching the FPR. The mod will not allow you to add any more timing than you already could add without the mod.

have you done this mod? can you actually prove that it does not work without heresay?? i'm going to try it. numbers are where the proof is.

The ECU does not use the O2 sensor when you floor the car. It uses its maps and that's it. If you run an adjustable fuel pressure regulator that allows you to adjust the pressure at full throttle, then you'll be adding more fuel when you floor the car.

you were talking about the car at idle! pick a line and run with it. stop jumping around. yes i know that we are dealing with a fuel map.

I am also telling you that unless you have a lot of work done to your motor, (what a "built motor means") like ported head, cams, header, exhaust, intake, large VAF, you know a lot of improvements to the air flow through the motor, your motor is already running fairly rich with the factory settings, so it does not need any extra fuel.

thank you for stating what "built" means in your dictionary. do you need all of those to be a built motor?

So, you can choose to believe me or not, but I do know what I am talking about. I am not trying to bash you or anything. I'm just sharing what I have learned myself after having worked on more BP motors than I care to remember.

i'll take your word that you have worked on a fair number of BP motors. i'll choose not to believe you. that is my position. Also i see what you are saying but i hold a difference of opinion. if you can prove me wrong get bring numbers/equasions to the table

[Tai Mai Shu]

now now.