My stock FPR is dying, what shoud I replace it with?
Another Stock unit?
Aeromotive Adjustable FPR?
Holley Adjustable FPR?
Hypertech Adjustable FPR?
Thanks!

 

I would replace it with another stocker. There will be no performance increase if you go with an AFPR.

 

A stocker is prolly as expensive as an AFPR.
Still stocker?

 

If they are roughly the same price, get the AFPR. It may not make any performance difference now, but if you upgrade injectors, add forced induction, or want to tune your a/f ratio in the future, it'll be nice to have...

BTW, the AFPR's will only really help at WOT in our cars. Under normal driving conditions, a higher pressure setting in the AFPR will just cause the computer to shorten the pulse width of the injectors, thus nullifying the fuel increase. However, when at WOT, the injectors open up and that is when the AFPR will allow you to get more fuel in...

 

not correct, the computer will correct part throttle as well as WOT pulse widths.

you have to change the injector constant in the PCM

jesse

 

OK so which AFPR to get?
(looking to place an order today!)

 

i bought the holley from summit. works great.

jesse

 

True, but the corrections at WOT are only partial corrections, so therefore some gain will still be noticed...

http://www.projecttransam.com/projects6.asp

Text Search for AFPR...

Not to say that that guy's word is fact, but he usually knows what he is talking about...

 

when you say gain, do you meen partial control?

 

An AFPR is the way Id go just b/c I believe aftermarket parts are normally superior to stock. Id set the AFPR at the stock pressure so you dont run overly rich or lean. the pcm will correct some of the error but not all of it so you have that chance of creating some problems if youre not careful. As far as power gains go... more fuel at WOT is just going to make you run rich at WOT so you shouldnt notice anything but a strong gasoline odor.

 

I agree, thats what i was thinking about.

 

Yes and no. If you have had your fuel already adjusted for a nice mix (i.e. custom programming), then yes, it will probably run a bit rich. If you are running forced induction, like nitrous or a supercharger, this is not a bad thing, since many tune for like a 11.5ish:1 a/f ratio when using forced induction. On the other hand, being n/a you are going to want something around 13ish:1 a/f ratio.

However, stock cars are often tuned to run slightly lean, in order to make them have better gas mileage. The are not leaned out to the point of burning ring or anything, maybe only like 14:1, but they are a bit lean none the less. An AFPR can allow just enough extra fuel to go in at WOT to get you back toward that 13ish:1 ratio that is optimal. In SOME cases, this can help to provide some extra horsepower at WOT...

 

AFPR is worthless get stocker. Nothing is better than delco parts IMO.

 

I put a Holley on mine, very happy with it, it was easy to install and it looks killer.
I had to move my wire loom that runs behind the manifold down so the AFPR would fit but it was no big deal.

 

Fact #1:

The stock programming on the LT1 is TOO RICH at WOT. The "target" A/F ratio, calculated by the PCM using the PE enrichment tables typically is about 11.7:1. This is too rich for peak power or peak torque... usually attained in the range of 12.8-13.2:1. If you simply use custom programming to lean out the stock programming at WOT, you will pick up about 15HP - dyno proven. You do not "tune" a 94 or newer PCM with an AFPR, but if you tried to do it, you would LEAN IT OUT, not try to richen it. You would be even more foolish to try and "tune" a nitrous or a blower motor with an AFPR.

Fact #2:

In the 94 and newer PCM's, when you alter the fuel pressure, you will alter the A/F ratio TEMPORARILY. If you lean the mixture out using the AFPR to reduce fuel pressure, you will at first see 15HP gained. As the PCM recognizes the leaner mixture, based on closed loop feedback from the O2 sensors, it will increase the injector pulse widths, using the long term fuel corrections. In closed loop, there is no change. When you go to WOT, and enter PE mode, the PCM will continue to use the long term fuel corrections (BLM's) from Cell 15, since they were "adding" fuel in closed loop. In effect, the PCM has negated the change.

Go to the ws6.com dyno tests, and look at his results for leaning the mixture out, by reducing the fuel pressure. I believe he gained 16.6HP, as shown in the dyno sheet. But, take the time to look at the "Note" below the dyno sheet..... he notes that the gain disappeared as the PCM made the corrections.

If you richen the mixture by increasing the fuel pressure, the O2 sensors will report the rich condition in closed loop, and the PCM will reduce the long term fuel corrections below 128, to shorten the pulse widths. Now that the PCM is "cutting" fuel in closed loop, when you go to WOT and enter PE mode, the PCM will now default to Cell 18, and lock the BLM's at 128. Hence, you WILL see a richer mixture at WOT, but that is the last thing you want on a stock LT1.

Stock closed loop programming for the LT1 (and virtually all cars, except some of the "lean burn" imports) is 14.7:1, the stoichiometric A/F ratio..... allows the cats to produce the minimum COMBINED levels of CO, HC and NOx, and gives decent fuel economy. That 14.7:1 value is hard coded in the PCM and can not be altered.... at least not by mere mortals.....