adjustable fuel regulator

[grygst76]

OK, I keep getting mixed responses to this one so I'll shoot it here. I have a 1994 camaro. I am running very rich and I am going to throw an adjustable fuel regulator in it. My own knowledge is that if I set the pressure to 38psi it will be 38psi, yet some think that the PCM adjusts for it and sets the pressure back to stock. How the hell does it do that? If I set it to 38, how does it bypass my setting to put it back to 45psi? Even if the PCM puts more voltage to the pump won't the regulator still give the injectors my set amount??

[Feral]

Well I know nothing about LT1's but unless there is some solenoid that can bleed off the pressure in the FPR then what you set it at is what you get ... but then again I'm used to rising rate FPR's and whatnot ... I should probably let someone more familiar with N/A's answer this so I don't look like an ass.

[grygst76]

See, that's what I figured since I'm used to older carburated applications I knew that you set it and forget it, but there was a lot of talk that the computer will overcompensate which I thought was :bs1: This my first pcm car I ever worked on myself but I have had and 88iroc, 92 vette, and a bunch of others that I just bought, beat, and sold and this is the only one I had interest in modding. Hopefully someone can chime in with an ultimate answer or real world application.

[forcefed6]

ok, get a fuel pressure gauge on the fuel rail of the motor.
back the afpr all the way out
turn the key on but not running and check the pressure.
this pressure should be your wot pressure
you should see a decrease of about 3-8psi i with the car at idle

also, you might have too take the afpr off too make sure that the diaphragm isnt destroyed already from cranking it.i had that problem a few times and i didnt no wtf was the problem. i found out that i owned the diaphragm like 3 different times so that could be the problem with it.

what kind of afpr did you get?

[grygst76]

Originally posted by forcefed6
ok, get a fuel pressure gauge on the fuel rail of the motor.
back the afpr all the way out
turn the key on but not running and check the pressure.
this pressure should be your wot pressure
you should see a decrease of about 3-8psi i with the car at idle

also, you might have too take the afpr off too make sure that the diaphragm isnt destroyed already from cranking it.i had that problem a few times and i didnt no wtf was the problem. i found out that i owned the diaphragm like 3 different times so that could be the problem with it.

what kind of afpr did you get?
None yet.....I wanted to make sure before I wasted my money on one since they are pretty costly. I think my regulator is shot, on my dyno run my A/F was 10.0 all the way across:ak1:
I'm hoping to lean it out a little for a few horses and better fuel economy..

[forcefed6]

why dont you hop on aim so i can help you better, lmfao
:smokin:

[grygst76]

Originally posted by forcefed6
why dont you hop on aim so i can help you better, lmfao
:smokin: @work right now and the web version takes to freakin long to load at this dump:sleep:
I'll be on @home tonight bout 8:00pm

grygst766

[540Malibu]

unless you have a bypass regulator or a fuel pump controller you will notice no difference.

[Mr Joshua]

why not get lower rated used injectors, with all the LT1's around here someone should have some old injectors hanging around
or a custom chip?
~J

[grygst76]

with lower rated injectors the cycle duty would be 100%. I am going 30lb due to what is going in it this winter but for the most part it's stock rated 24lb. I want to see an improvement @WOT only, not cruising around..I know if I lean it out a little I can free up maybe 10-15 more ponies:thumbsup:

[tims]

Well I don't know exactly how the camaro fuel system is set up, but in generally the FPR is hooked directly up to the manifold pressure, so fuel pressure will be base pressure - manifold vacuum. I use an Aeromotive FPR which does just fine, and costs about $120. The ECU should have absolutely no controll over the fuel pressure unless there is a solenoid between the FPR, and the manifold. Also N/A FPR's (or fuel system in general) is not different from a turbo, The N/A still requires a rising rate FPR to compensate for vacuum. By design if the FPR see's boost it will increase the fuel pressure. It seems to me like adjusting the A/F ratio by lowering the fuel pressure, or installing small injectors is not the best of methods.

[540Malibu]

Originally posted by tims
Well I don't know exactly how the camaro fuel system is set up, but in generally the FPR is hooked directly up to the manifold pressure, so fuel pressure will be base pressure - manifold vacuum. I use an Aeromotive FPR which does just fine, and costs about $120. The ECU should have absolutely no controll over the fuel pressure unless there is a solenoid between the FPR, and the manifold. Also N/A FPR's (or fuel system in general) is not different from a turbo, The N/A still requires a rising rate FPR to compensate for vacuum. By design if the FPR see's boost it will increase the fuel pressure. It seems to me like adjusting the A/F ratio by lowering the fuel pressure, or installing small injectors is not the best of methods.

this is wrong, power adder regulators add fuel, n/a regualtors keep fuel constant, vacuum - fuel = melted pistons. 90% of ECU's compensate for vacuum changes solely by pulsewidth.

[tims]

I don't know where you get your figures from, but many N/A's use manifold pressure to regulate the fuel pressure just like forced induction engines. There remains no inherint difference between forced induction fuel injection, and N/A fuel injection, other than a larger range of pressure differences. Power adder regulators do not "add fuel", they keep the pressure diferential between the fuel rails, and the intake manifold constant. Any forced induction engine also COULD regulate fuel by compensating the injector duty cycle, it simply would require a larger range of adjustment, and would probably have no benefit. This you should see a decrease of about 3-8psi i with the car at idle Indicates that the car probably does in fact regulate the fuel pressure based on manifold pressure, not just compensate by adjusting the IDC.

[540Malibu]

Originally posted by tims
I don't know where you get your figures from, but many N/A's use manifold pressure to regulate the fuel pressure just like forced induction engines. There remains no inherint difference between forced induction fuel injection, and N/A fuel injection, other than a larger range of pressure differences. Power adder regulators do not "add fuel", they keep the pressure diferential between the fuel rails, and the intake manifold constant. Any forced induction engine also COULD regulate fuel by compensating the injector duty cycle, it simply would require a larger range of adjustment, and would probably have no benefit. This Indicates that the car probably does in fact regulate the fuel pressure based on manifold pressure, not just compensate by adjusting the IDC.

when you learn something about how this stuff works with GM fuel injection, come bcak and post something useful.
1. n/a motors dont have manifold pressure

2. Not all boost sensitive regualtors are a 1:1 ratio so this shoots your pressure differential theory down the shitter.

3. The pressure decrease at idle is to keep atomization efficient, theres no need to piss full force into the wind when there istn any wind.

[tims]

1 N/A motors DO have manifold pressure (in absolute terms), it ranges from about 1/3 atm to close to 1 atm depending on throttle position. The entire purpose of the throttle plate is to controll manifold pressure.

2. Hardly, most rising rate FPR's are 1:1, turbo or NA (of those that regulate based on pressure input) you could increase the fuel pressure more, but thats another story entirely.

I'm not sure why you think that lower fuel pressure has better atomization, but I do agree that theres no need to piss into the wind when it isn't there, you certainly don't need as much fuel pressure at idle.


I don't claim to know everything about GM fuel injection, but I'm curious, if the GM units do not change fuel pressure based on manifold pressure, why do the aftermarked LS1 regulators have a nipple for a manifold pressure source?

[grygst76]

Originally posted by tims
1 N/A motors DO have manifold pressure (in absolute terms), it ranges from about 1/3 atm to close to 1 atm depending on throttle position. The entire purpose of the throttle plate is to controll manifold pressure.

2. Hardly, most rising rate FPR's are 1:1, turbo or NA (of those that regulate based on pressure input) you could increase the fuel pressure more, but thats another story entirely.

I'm not sure why you think that lower fuel pressure has better atomization, but I do agree that theres no need to piss into the wind when it isn't there, you certainly don't need as much fuel pressure at idle.


I don't claim to know everything about GM fuel injection, but I'm curious, if the GM units do not change fuel pressure based on manifold pressure, why do the aftermarked LS1 regulators have a nipple for a manifold pressure source? Because the LS1 uses an adjustable unlike the LT1 that we are talking about.... 2 seperate motors using 2 seperate technologies.:sleep:
Anyways some people have told me that the PCM compensates for less pressure by changing the duty cycle of the injectors, I wish I could get a solid answer......

[Feral]

Originally posted by grygst76
Because the LS1 uses an adjustable unlike the LT1 that we are talking about.... 2 seperate motors using 2 seperate technologies.:sleep:
Anyways some people have told me that the PCM compensates for less pressure by changing the duty cycle of the injectors, I wish I could get a solid answer......

Actually that is what I've been told as well. In that case then with an adjustable FPR you just reduce the pressure and there you get your better fuel curve. Pretty easy really ...

As for atomization ... Spence are you saying that it is better no to atomize on an N/A? Does this just heat up the fuel unnecessarily ... or make the fuel too well atomized so that it doesn't flow right into the cylinders?? Just curious ... I've had my head stuck in my turbine for too long.

[grygst76]

Originally posted by Feral
Actually that is what I've been told as well. In that case then with an adjustable FPR you just reduce the pressure and there you get your better fuel curve. Pretty easy really ...

As for atomization ... Spence are you saying that it is better no to atomize on an N/A? Does this just heat up the fuel unnecessarily ... or make the fuel too well atomized so that it doesn't flow right into the cylinders?? Just curious ... I've had my head stuck in my turbine for too long.

With the way the manifold is set up on an LT1 the injector is aimed right at the valve for a straight shot so atomization is truly not a big deal, although from what I read is some people have modified the LT1 intake to deliver a more presise shot and with better atomization to get an extra 35 horses off that mod alone!! Too much work was involved with doing it.. I used percy's intake gaskets on my 327 that had a screen in the port and it supposedly worked to better atomize the fuel, I did not feel a SOTP change, but my gas mileage went from 7 miles to the gallon to 7.2:thumbsup:

[540Malibu]

Originally posted by Feral
Actually that is what I've been told as well. In that case then with an adjustable FPR you just reduce the pressure and there you get your better fuel curve. Pretty easy really ...

As for atomization ... Spence are you saying that it is better no to atomize on an N/A? Does this just heat up the fuel unnecessarily ... or make the fuel too well atomized so that it doesn't flow right into the cylinders?? Just curious ... I've had my head stuck in my turbine for too long.

at idle full fuel pressure will cause the fuel to puddle against the runner floor and the valve....in a SBC, henco poor atomization.

[TunedPort 335]

Originally posted by 540Malibu
at idle full fuel pressure will cause the fuel to puddle against the runner floor and the valve....in a SBC, henco poor atomization.

Sort of like what happens when you polish the intake ports. Fuel puddles up

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