I am not running rich at the low end. My fuel trims are stable within factory specs.
I'm not sure where your prediction comes from, but my statement comes from experience on my own car. And it was predicted by enough good experts before attempting it, that I fully expected the positive outcome that I achieved.

My particular case is different because I increased the top end flow of my engine dramatically with a Gen3 swap and extensive porting. I needed higher fuel pressure across the band.

How are you not running rich on your low end? You just admitted yourself that you were running lean on the high end. So if your low end was fine and now you raise base fuel pressure which will give more fuel all the time. How are you not running richer on you low end? Or were you running lean on your low end too before the FPR?

Your fuel trims are prolly within factory spec but they didn't get any better or any closer to 0 when adding the FPR.

You got me their - I have never ran a adjustable FPR on my car but I'd never would want to anyways. Their are better and more accurate ways to add fuel.

Also I don't know why you use the word 'predictions' - this is common sense we are talking about here.

I was running lean on the low end as well. More air requires more fuel. As I stated before, I did a Gen3 swap on the car. Including the larger throttle body.

I suggest you try an adjustable FPR yourself before stating it doesn't work. The PCM has a neat way of regulating your AFR for you.

2000SilverBullet and I are both running adjustable FPR'* with great success. My car recently posted 31mpg AGAIN just over a week ago on a long freeway trip. Doesn't seem to be running rich on the low end, does it?

There are probably some applications that an adjustable FPR won't work for, but with my setup, it was the ideal solution.

Edit:
Just got this via PM. Maybe it can explain things in simpler terms.
This is assuming your MAF sensor is calibrated (chosen) to match the range of flow you would see from the bottom end to WOT. And assuming your fuel injectors don't go static before WOT trying to achieve it. Which is exactly WHY the adjustable FPR works. I'm only aware of two cars here on this Forum that have even tried it, and both of us love it.

Anyone else have supporting or opposing EXPERIENCES?

Where did I say that it didn't/wouldn't work? I just said their are better ways to add fuel. Like I said I'll never use an adjustable FPR because their are better ways to add fuel.

Yes the PCM does regulate you AFR and adjust your fuel trims but which car would you rather have one with the fuel trims locked on 0 or one where they are all over the place?

no point in arguing with llBlazin_llLo, he'* always right.

Mine aren't all over the place. And you've experienced this phenomenon?
The PCM learns the new fuel curves very quickly. It took just a few normal and spirited runs for my very intelligently designed PCM to figure out something had changed. My MAF sensor, TPS, and O2 inputs gave the information to the PCM that it needed in order to compensate for the higher fuel pressure and maintain my Air/fuel ratio properly.


And an adjustable FPR is a much better option than a linear or step-linear AFC calibrator.

Good one...

Your comment is the one offtopic. It seem to me that Willwren is the one that seems to think he is always right.

if thats what helps you sleep at night

You bet Blazin. Particularly this time around. You see, I've actually DONE what you claim won't work. As has 2000SilverBullet.

But of course, even though you've not done it, you know best. I think this whole topic could use a reminder of the original topic:

Derek blew his motor. He'* building a new one. He doesn't need an adjustable FPR at the present time.

If anyone would like to start a NEW topic on Adjustable FPR'* and the magic way the PCM helps you tune, feel free.