I Know that an Adjustable Fuel Pressure Regulator (a complete new adjustable one not the half of a stock regulator that needs to be modified) will raise fuel Pressure on a N/A car at WOT.

1. Will it do the same on a car with boost at WOT? (Please explain.)

2. If it raises Fuel Pressure, will it raise it according to Boost?
Ie...Like 10# of boost on the intake, would it increase by 10 psi of Fuel Pressure also?

3. Will most aftermarkert AFPR do this or does it have to be a Boost Sensative regulator (not an FMU)?

Thanks for any input,

 

If the regulator is boost referenced, which most aftermarket EFI regulators are, then it will raise fuel pressure at a 1:1 rate with manifold pressure. Just be sure it's boost referenced and you'll be fine. If not, you'll need alot of tuning on the fuel map to account for it, and your injectors will lose efficiency as the pressure differntial between the manifold and the fuel rail declines. The injectors won't atomize the fuel as effectively.

 

Cool...Thank You....

 

Any 1:1 regulator can be used on any stock car out!!! What you said is half true in this instance. Your statement is completely true for a car that has a turbocharger stock. When you add a turbocharger however, it's completely different. GM didn't tune these cars for turbo's. They tuned them for N/A. Turbochargers require so much extra fuel it's pathetic.

You need a FPR that is made to go on a N/A car with a turbo upgrade. Vortech has the best one out from my personal experience. The S-FMU is rock steady, it's does not move if it's set. The really nice thing about the Vortech is that it uses disks to control the raise rate. They are like $20 each but if you need just a bit more fuel it's the best thing out. I think the smallest they make is with a 6:1 raise rate, could be 8:1 though and the highest, I believe has a 12:1 raise rate. LS1's were NOT meant to see positive crankcase pressure. You will need that extra 8 gallons of fuel for every 1 pound of boost. A 1:1 will NOT cut it for a turbocharger fuel system on a N/A car.

There are a couple exceptions though. You could do what I did and add more fuel injectors but I doubt there is any room on an LS1 manifold. You could also get the PCM reprogrammed to push that extra fuel but not sure how much that runs and if it can be easily changed with whether conditions like a FPR can be. Good luck!!

 

I'd like to know what oem (LSx Or LTx) pcm can be reprogrammed for anything above 101.3 kpa.? IOW, boost referenced. Any fuel or ignition mapping not referenced to boost is guesswork.

 

What! GM didn't calibrate the stock fuel and ignition curves for forced induction. No kiddin', who woulda' guessed. Those cheap bastards!

A boost reference AFPR is the same regardless of whether the car was originally naturally aspirated or turbocharged from the factory. There's no difference. If you think a 1:1 fuel pressure rise to boost will not cut it, you don't know what you're talking about, as that is the standard pressure rate used by every boost referenced AFPR on the market.

BTW, an FMU is a band-aid approach and is not the equivalent of an AFPR. Anyone who suggests using one over a boost referenced AFPR along with a proper recalibration of the fuel/ignition maps is steering you the wrong way! Half-arsed setups are what give forced induction systems a bad rap.

 

Has turbo'd non turbo car. Has tried 1:1 FPR, didn't CUT IT!!! The S-FMU is damn awesome and better than any AFPR on the market that has a higher raise rate than 1:1. Go ahead though, use a 1:1 and not have enough fuel.

 

The only time you'd use an FMU is if you're not properly recalibrating/tuning the ECM to control the injecter pulsewidth under manifold pressure. No serious engine builder or tuner would use an FMU of any kind over a 1:1 AFPR and a recalibration of the ECM's fuel/timing maps.

Yes, I use a 1:1 AFPR, and with the a proper tune in my FAST, I have plenty of fuel, enough to make 1200hp on 93 octane at 20 psi of boost, dyno proven, without even pushing it hard.

 

Thanks for all the great response guys.

I was planning for Bryan at PCMForless to tune my car personally (Not mail order tuning) with my Adjustable fuel pressure regulator, a 255 LPH Walboro intank pump (high pressure/high volume GSS340 Model pump) with 50# MSD injectors and I did get a Racetronic wiring harness to boost voltage and a amps to my pump (not the boost a pump...just a hard wiring harness to the alternator). Check the sig to see the more of my mods..

Bryan told me he has tune a couple of cars with the 50# MSD and came out with favorable results.

Thanks again...The responses are much appreiciated!

 

Luckily, your ECM can be reprogrammed. Mine can't so I should use a FMU or similiar but I also use 1:1 because of certain circumstances that just show how pimp I really am. But, yes, Better!! I believe I said he could get it reprogrammed. didn't I??

 

I think this has wandered a bit..
A 1 to 1 FPR will not add enough fuel if you don't run the proper injector size, AND recal the ECU

The FMU WILL add enough fuel to "crutch" the fuel curve and make it run, and is easier and cheaper than doing it the "proper" way, that is why the SC manufactures choose it.

I personally chose to go bigger injectors, more pump and line, 1 to 1 AFPR, and retune the ECM.. mainly because I plan to go bigger down the road, and don't want to have to keep "re-crutching" the combination..

It's like that old commercial,.. "you can pay now, or pay later!"

 

If a AFPR is rated for 20 to 65 psi and you are running an FMU that is at an 8:1 ratio, will the pressure destroy the AFPR???

I have a Holley 512-501 that needs to be readjusted after running boost as it loses the pressure setting??? Drops a few psi. Brand new.