i just put on a aeromotive fuel pressure regulator on my 97 ss and out the box it was putting out like 52 psi to the injectors, i toned it down a notch to about 47 or 48 psi and im not sure if thats even safe. Mods that ive done are ignition, headers, throttle body, 1.6 roller rockers, valve springs, ive got a cam just got to put it in.. so if any one has any feed back on what would be an ideal pressure let me know.. The regulator has a range between 35 and 70 psi. I also just ordered some 26lb injectors and wanted to know what kind of difference those might make over the stock ones. thanks

 

43.5 is stock fp. Just FYI

 

absolutely nothing. no reason to change out stock injectors until the engine is generating over 370rwhp.

 

You're wasting your money big time.... with your mods, the STOCK injectors and the STOCK fuel pressure (43.5psi with the vacuum compensation line disconnected) are totally adequate. You can't "tune" with an AFPR and you can't improve performance, unless your injectors are at 100% duty cycle, and yours aren't.

The way you have it set now (particularly if its running 48psi WITH the vacuum line attached) is over-fueling the car by about 12%. While the long term fuel corrections may be able to prevent it from running rich in closed loop (part load), when you go WOT, you are pouring in 12% extra fuel and possibly washing the oil off the cylinder walls and causing damage.

Additionally, the Aeromotive AFPR's have failed numerous times, and are extremely unreliable.

 

thanks for the info, i better make some adjustments..

 

Found this thread in a search ...

I race in a class that LIMITS horsepower so all cars are evenly matched, like with stock 5.0s and 4.6s.

So, I have to run a restrictor plate to limit HP. A by-product is a very rich mixture ... REALLY rich.

EVERYTHING including the computer, HAS TO REMAIN STOCK. So that is NOT an option.

One of the few changes allowed is an adjustable FPR.

If I adjust the fuel pressure down below stock to some point, will it keep the motor from running so rich?

Can anyone speculate on how the HP and TQ curves would be altered?

Again, it's not peak numbers I'm seeking, rather flat, table top looking curves.

 

Maybe some info on your setup is in order. Restrictor plate on an LT1? As already inferred, on a MAF car, the computer tune (w/sensor input) controls the a/f ratio, not fuel pressure.

 

If you reduce your fuel pressure, the PCM will increase the pulse widths to maintain the same amount of fuel delivery, in closed loop (part throttle/part load). When you go WOT, since the PCM was adding fuel with the long term fuel corrections, it will continue to add the same ratio of fuel at WOT, and you will not have changed the A/F ratio in any way.

As Shoebox mentioned, if you have a 94-97 you have an MAF, and the MAF reads the actual mass air flow into the engine, whether there is a restrictor plate in there or not. It will not run rich just because you added a restrictor. If you have a 93 speed-density, the restrictor plate will reduce the air charge density, and the speed-density will pick up the reduced air mass flow. Where you might get into trouble with speed-density would be if the restrictor reduces volumetric efficiency, and you have not altered the VE tables. In that case, you would possibly be running a bit on the rich side with the restrictor.

 

Setup is a bone stock OBD2 LT1 ... it has a crank position sensor, so that would make it a 96 or 97, right?

I currently run a 35mm plate between the TB and intake and get 234HP/297TQ.

The problem I'm trying to solve is that the 297TQ is at ~2800 rpm and drops like a rock from there. I'm wanting move that peak up the rpm range.

Again, I'm limited to OEM stock components.

Also, it was stated above that the Aeromotive FPR is prone to failure. What is the failure mode? What's the preferred AFPR?

And for what it's worth, I'm having to source a FPR anyway as my fuel rails have nothing right now. My GM hookup shows the regulator at $45 and the associated components needed to hook up the return at $75 and a seal kit for $10.

Thanks for the input ...

 

when my car was bone stock the fuel pressure was about 37psi(vacuum disconnected), so i bought a AFPR, and set the pressure to 45psi, after that the car worked much better and responded to throttle better.

 

Aeromotive had a lot of problems in the early 2000's with failed diaphragms on the LT1 AFPR's. They blamed it on a change in gasoline composition that they had failed to pick up on. The claimed they upgraded the materials of construction to work with the new blend, and sent someone here to offer a free replacement, no questions asked, for anyone who had a problem with the AFPR's. That was several years ago, but problems seem to persist. Every time Aeromotive gets mentioned, one or two people will chime in mentioning that their LT1 AFPR failed. Note - this is not a condemnation of Aeromotive, or their products. They make some great stuff. But following these cars on numerous bulletin boards, I've seen numerous reports of failures. A common problem is an inability to adjust the pressure down to stock. I hate to even mention this, because it upsets one member in particular, and I always run the risk of starting a war of words... but I'm just telling you what I have observed over the past 7 years.

 

I had one AeroMotive APFR fail due to diaphram leakage. Took some time to troubleshoot. Remember to check the vac/ boost ref line for fuel (if wet - it leaks). AeroM would not replace it (I called them). Now I have another (Summit). I'm waiting for it to fail, but, now I know what to look for. You would think they could offer a replacement part for the diaphram, but (I guess) not. It can be changed out very easy. Thinking of fabbing my own diaphram.

 

Who makes a good AFPR for the LT1?

 

It keeps coming back to the question.... why do you want one? There are legitimate reasons, like raising fuel pressure to increase the flow rating of the injectors, and reducing duty cycle. But most people don't need to do that.

Check the Supporting Vendors, linked at the top of every page. Thunder Racing sells a Metco "conversion" kit for the stock requlator. They also sell the Aeromotive. T. Byrne has a "no name" AFPR. I had a great one, unbranded, from IRS, but they went out of business many years ago. Currently running a Weldon unit, but it is not a stock replacement.

 

Not trying to hijack the thread, but if "ZX636RIDER03" tried lower fuel pressure AND pulled the ECU fuse to reset it to factory defaults wouldn't he get the effect he wants for the first event or two (after warming up the engine to get to closed loop operation) before the ECU "learns" that it has to increase the injector duty cycle? Any info on how long it takes the ECU to adjust it's fuel tables to compensate?