I've always heard that an AFPR is a good upgrade. I was reading through the TGO FAQ page, and on a stock 350tpi they gained 58ft/lb torq and 19hp by uping the fuel pressure to 50lbs. What am I missing here? SURELY this isn't right? That's a huge increase for just installing an AFPR. I've searched and read a lot of threads and none of them talk about this kind of performance boost. Please set me straight.

little less then half way down

https://www.thirdgen.org/newdesign/faq/thirdgen.shtml

Phyte

yeah i've read that a few times too. dunno how they managed that one. i've seen 10-15hp from uping the fp though. not 50.

IMO you should never run a psi other than what your injectors are rated at by the manufactuar. You can hurt your fuel pump and/or your injectors.

Tune it right and make changes in your chip, why risk damage to other parts...

I installed a Holley AFPR just because my stock one could not hold it's correct pressure at higher RPM's. I have my Holley set for 43.5psi which is what Accel rates my injectors at and what GM happens to rate stock third gen injectors at. Then I tune my car in my chip...

My '99 LS1 Camaro SS runs 58psi fuel pressure from the factory and I have run as high as 56psi on my '87 IROCZ, which is now set at 52psi.

So, I say run the fuel pressure that the engine likes. If its 50psi, then run 50psi. I dont see how any "damage" could be done to the fuel pump or the injectors. The main issue is the fuel injector constant that is programmed into the Eprom chip. Another issue is: can the fuel pump keep up with the dialed in fuel pressure.

The 19 Hp gain mentioned above seems a bit high, but 10 to 15 is believable, so why not 19. Could be the MAF sensor flows alot more air than it reports out to the ECM.

Well, I just read the FAQ, the peak Hp gain seems to be in mid-range and is in the 40's. However, at 5000RPM, the Hp gain is 9.7Hp.

Simply put, They are giving the engine The fuel it needs. There are many posts pointing out that the ECMs try to bring your Air fuel ratio way down in order to compensate for emmissions requirements. Later engines could use higher pressures and bigger injectors partly beacause of advances made in engine management. ie SFI and Alterenating squirts and cats.

IS 50PSI with the vac line disconnected? (I guess so but want to be sure...)

Between tuning and upping the psi, I would have to say tuning is better.

It is only 20hp gain, I saw someone say that they didn't see how they got 50hp gain. I have seen more than this come out of tuning.

As for why it gains more power, what I have read all says the same thing, when you up the psi behind the injectors (more than the rating) it gives it better atomization. Basically the spray can turn into vapor faster, which in turn mixes with the air better, believing that it gives more power. I have seen the power out come, but I don’t fully understand it, that’s just what the magazines say.

Of course if you are putting too much fuel in, or already max amount to burn, you will lose power with wall washing or just being to dang rich.

Still say tuning is better.

the 50 hp. can be seen in open loop due to it controling the fuel moreso than the sensors, but this gain will not be seen in closed loop. so you say well why not run my motor in open loop and get 50 more hp? well because drivability will suffer along with fuel economy. the motor was designed to run in closed loop so don't even consider oposite.