Ok, so I was perusing through the FAQ and came across some dyno results that are rather hard to believe concerning an AFPR on a stock 350 TPI.

So... after doing some simple math the dyno results show me that a stock 350 TPI makes these numbers:

Stock@42PSI (stock fuel press.)
Avg. 241.78 RWTQ from 3,000-4,000 RPM
Avg. 189.64 RWHP from 3,500-4,500 RPM

Stock@50PSI (w/ AFPR)
Avg. 305.52 RWTQ from 3,000-4,000 RPM
Avg. 224.22 RWHP from 3,500-4,500 RPM

Can someone shed some light on these claims? I find it rather hard to believe that a stock 350 TPI gains 60 avg RWTQ and 35 avg RWHP from an 8lb bump in fuel pressure. If this were the case I'd imagine an AFPR would be the very first mod everyone would do!

 

Also - I was told by a friend who happens to be a motorhead that I should get a high volume fuel pump if I plan to run 50psi. However I'm not sure he knows stock details of f-body components so I wanted to run this by everyone to see if he's accurate.

 

IIRC that table was copied from TPIS propaganda. Even if they actually measured those numbers they no doubt were pulling every trick in the book to inflate the gains.

No, there really isn't anywhere near that much power to be had just from an AFPR.

The stock fuel pump can maintain 50psi no problem on a stockish engine. Once you're inside the engine though (heads/cam) you might need more fuel than it can send. Pressure and flow are an inverse relationship. I.E. fuel pump flows more at lower pressure than high pressure.

 

I figured! So what would more realistic gains look like? Maybe 8 or 9 tq and 5 or 6 hp throughout the band?

Someone should note that those gains are from TPIS... that's misleading.

 

When I made my 350 engine swap and dyno'd the car It was running rich and the power was down. Replaced the stock 305
FPR with a adustabe one and set the fuel pressure at 43PSI and re-dyno'd the car. Results the air/fuel ratio was right on and gained 11 RWHP over the first test just by using AFPR.
But I do question that posted gains.

 

yeah, it seems a bit much, but in GMHTP a guy runnin stock manifolds, stock converter, stock rear end, and stock heads and cam went from 14.3 to a 13.8 or something with an AFPR set at 51 PSI and a modified PROM. It was basically a car with all free mods, a custom chip, and AFPR, that's pretty impressive, but I'd still like to see a timeslip or something. I think he also set his timing to something like 12* advance. Still seems hard to believe, maybe he had a factory special or something like a some of the few 5.0s that ford dumped out that seemed to perform better than any others.

 

I have a AFPR.

I set it at 43 PSI and left it there.

whooopty do.

If I need more fuel someplace, I add it in the chip.

If I hit 100% Duty Cycle on my 22 lbs injectors, Ill get bigger injectors.

IMO it's not really nessicary if you have the ability to burn PROMs.

If you don't burn PROMs - time to get started.

 

I dynoed my Iroc at 50psi with the stock injectors and it made 236HP @ 4500 RPMS and 325FT-LBS @ 3600 RPMS
I ran it again at 48psi and I gained 9HP & 10FT-LBS at the rear wheels. This was with just bolt ons. My 383 however requires more fuel obviously so it liked it better around 52 psi

 

Yeah - I plan to learn the basics of prom burning sometime in the near future... there's so much potential trapped inside the weak *** factory tuning that I can't ignore it for to much longer. I believe a bone stock L98 can run good times with just a little tuning and good driving - so it only makes sense to tune a prom when you're freeing up power with better parts. Ehhh, I'll get around to it!

 

i dont have dyno results to prove anything, but i can tell you by seat of the pants an afpr makes a hell of a difference. i had my pressure set at about 47 psi and wanted to see what would happen if i turned it up a little. acceleration was great at 47 psi, but then i turned it up to about 49 and my head became pinned to the headrest. thats pretty noteworthy with just a 2psi difference. also with the tpis stuff, they were burning new proms to complement the fuel pressure changes, but they were getting like 10 to 15 horsepower at the crank with stock proms

 

You can't tune a car with the butt dyno. You will inevitably just end up going way way rich. Even i fell into that trap last year. I was too busy with work to get in as much track time as i wanted, but i made a series of chips with a few tweaks and adding fuel, and it kept feeling better and better.

Well, when i finally got to the track i was down 3mph. I got 2.5mph back by dropping 8psi of fuel pressure and taking another 10% of fuel out in the chip.

Rich feels fast. Lean is fast. Don't waste your time tuning by feel unless you don't mind killing performance. I really thought my car was runnig great with all that extra fuel in there. And when i took it all out at the track, it did almost feel less snappy. But numbers don't lie, the more fuel i took out, the faster it went.

BTW, as for just doing your tuning with the chip, thats not all true. While you can do all your tuning in the chip, an AFPR is a nice way to do quick adjustments at the track. Especially if you can't burn new chips on the road, it's almost necessary IMO.

 

The AFPR is too general to really be of much use IMO.

Unless your entire fuel map is Rich or lean - Adjusting to solve a problem one place is only going to Cause other's. Your going to be Making Compromises, alot like you would Tuning a Carb (hmm...)

Power Inverters Cost 30$ At Kragans - helluva lot cheaper than a AFPR and let's you burn chips wherever you feel like it