I was wondering if there was any pros or cons to intalling an adjustable fuel pressure regulator.The reasoning behind this is that I have an Ecotec supercharged with the GM flash and now running a 3.0 pulley. At WOT nearing redline the AFR begins to climb into the 11s which I take as the injectors maxing out. I've read that some people raise fuel pressure (via an adjustable FPR) and install higher flow fuel pumps to richen things up while maintaning the same injectors. So thus I wonder if I can accomplish lower AFR by raising fuel pressure. Are there any negatives to raising fuel pressure this way? Previously I was seeing 62.5PSI at WOT, but for some reason now I only see 60PSI, is this normal?

I don't know nearly as much about superchargers asi do turbos but your afr climbing into the 11's doesn't seem like something you should be concerned about, i think that is still a safe level to be at. As for raising the fuel pressure, this will richen up your mixture for sure and depending what injectors your using, your probably not maxing them out. I'm sure you have been told this before but your best bet to get the maximum out of your supercharger is to get it tuned with HP tuners then you won't have to worry about increasing your pressure and you can get much more out of your injectors. hope this helps.

Get a real tune and stop being a ricer.


1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by: Kronos Performance

WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer

Thanks, Cody. I know the GM flash is a crap flash, but that's what I have for now. I personally also think 11 is not bad, but I saw a post from old skool saying that pushing these smaller pulleys on the GM flash was crazy and that we're possibly pushing the duty cycles past the safe zone on the supercharger kit injectors which I think are either 32 or 34 lbs.

they are 36's

Afr in the 11's is nothing to be concerned about, infact thats a bit on the richer side. A 1:1 afpr wont help much for wot but more for base pressure, but an fmu would help as it adds more fuel per psi(common ones are 12:1 for example). And of course best way would be to actualy tune but since youd need a new pcm thats not flashed, an fmu would work fine as a crutch. But I wouldnt worry about leaning out until you see afr's in the upper 12's or higher

Leafy (Club Jeffie FEA man) wrote:Get a real tune and stop being a ricer.

Hey that hurts dead inside man, lol. Naw but you're right I need a good tune. Quick questions, will the car pass emissions with a HP Tune or Trifecta Tune?

icemike89 wrote:Afr in the 11's is nothing to be concerned about, infact thats a bit on the richer side. A 1:1 afpr wont help much for wot but more for base pressure, but an fmu would help as it adds more fuel per psi(common ones are 12:1 for example). And of course best way would be to actualy tune but since youd need a new pcm thats not flashed, an fmu would work fine as a crutch. But I wouldnt worry about leaning out until you see afr's in the upper 12's or higher

So those Accel or Aeromotive AFPR won't really assist me much during WOT? The big reason I want to see how safe I am is cause I want to downsize some more to a 2.9 or 2.8. I once heard of a member running around with a 2.9 and no problems with the GM flash. But I think 2.8 is pushing it. Even the Cobalt guys won't run 2.8's without 42 lbs injectors and the re-tune.

11's are good sae AFR. You can have a good safe AFR, but be pushing your injectors past a safe duty cycle. Only way to know if real datalogging to log injector duty cycle.

So what is your AFR in the lower RPM's at WOT?



FU Tuning

I know that under heavy acceleration (50%+ throttle) and at WOT AFRs are at 10.1-10.3 as long as I am under I would say 4.5k RPM. After that I start touching low 11s and I think when I top out on speed I saw them in the low 12s, I think, can't remember for sure.

i think 10's are rich @4500 rpm,in fact mid 11's @wot sound pretty good to me.this is what i think is commonly accepted around forums .

14:1 - 15:1 @ idle.
13:1 - 13.5:1 @ normal driving
11.5:1 - 12:1 @ w.o.t.

Yeah those 10's are way too rich for any motor, but more so for a Eco.



FU Tuning

what does your car idle and cruise at?

Okay, well I lied, lol.

The car idles at 500 RPM (A/C off) to 650RPM (A/C on)
It cruises at 1550 RPM @ 45 MPH

14.5 - 15.1:1 @ Idle @ 40 PSI (A/C on)/43 PSI (A/C off) fuel pressure
14.1 - 15.3:1 @ normal driving @ 45-50 PSI fuel pressure
12.3:1 (under 4k RPM) to 13.5:1 (6K+ RPM) @ W.O.T. with fuel pressure jumping to 58 PSI at first and then linearly dropping to 48 PSI before shifting at Redline.

I think I need to find a way to maintain my fuel pressure at W.O.T. to lower AFR.

I am looking into buying a LT1 Adjustable Fuel Pressure Regulator, but they all seem to be missing the bushing with the o-ring on the return side. Does anybody know where to get that bushing so as to press it in and be able to use the stock lines?

13.5:1 at wot is dangerous. get larger injectors and tune it. simple as that. dont waste your money on a primitive fmu. it will richen your high rpm afr's but it will also richen your low and mid rpm afr's. not to mention its will raise your fuel pressure so high injector damage can occur. tends to kill fuel pumps quickly. i wouldnt want to drive around with 100+ fuel pressure anyway.. scary!!!!!

He said he wanted A boost referenced 1:1, not an FMU. It sounds like it would take care of his problem.

I'm not sure. Depending on your money situation and the moment you would be best off getting it tuned, but like most of us you probably don't have money out the ass. If you can afford to get it tuned, do so, it is good insurance to make your motor last longer. If not look into bigger injectors possibly or the 1:1 LT1 regulator. I'm not sure myself whether or not your injectors are big enough, someone on here might know or possibly the person who would be tuning your car. Good luck!

I think he does have a problem with the FPR. A Ecotec should hit around 62psi at WOT. So a new FPR, or AFPR might get it more safe.

After sayign that a real tune is the only way to go.



FU Tuning

Screaming for Mercy!! wrote:I think he does have a problem with the FPR. A Ecotec should hit around 62psi at WOT. So a new FPR, or AFPR might get it more safe.

After sayign that a real tune is the only way to go.

You are absolutly right. It use to hit 62 PSI with the 3.1" pulley all the way to the redline with AFR at around12.5 max.
Now with the 3.0 I only hit 58 PSI and begin to drop to 48 PSI as I hit redline. I switched it with a new FPR and the numbers are stable now, but still low, 50 PSI at WOT.

I did get myself an adjustable LT1 fuel pressure regulator, but even with the regulator set at 60 PSI WOT, it would still drop to 50 PSI when driving at WOT.
I think the injectors are just running at the max and fuel pump isn't supplying enough pressure.

If the pressure is dropping its the fuel pump.


1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by: Kronos Performance

WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer

Leafy (Club Jeffie FEA man) wrote:If the pressure is dropping its the fuel pump.

Yeah I was afraid of that. And I just put that pump about a year ago, probably no more than 20k miles.

racetronics, w body pump.


1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by: Kronos Performance

WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer

and remember this. just becuase it says its 1:1 doesnt always mean thats what it is. i know some are low, and mines a bit high. mine is more like 1.2 or 1.3 :1 they will all vary slightly.

Leafy (Club Jeffie FEA man) wrote:If the pressure is dropping its the fuel pump.

Exactly. Pump is starting to make it's way out.

racetronic is the way to go.



FU Tuning