I was sitting on the thrown (a little graphic) reading jegs to try to get an Idea of how much lph would support 700hp. I found an add for aeromotive they have a pump that will support 800hp forced induction efi. It flows 600lb ph at 45psi, so I was thinking that for every 100hp FI you would need about 75lph So wouldn't I need 525lph? Or am I missing something? Wait no that can't be right, because parish is only using two 255's and he is over 1000hp. I think I am missing something! PSI!

 

wait, so the stock 5.3 short block can handle 20 psi? or did i miss something?

 

First, the inline pump won't add volume, just keeps the volume your intank pump is sending at a higher pressure. But if you are flat out using more gas than the intank can provide, no inline pump will help you.

The stock pump is in the 160-170lph range and can only support up to around 550-580 flywheel. You're way past that which is why you're dropping your fuel pressure (because of lack of fuel volume).

There's no way you are at 80% IDC on 43s at that power level. You've got to be near 120% -- in other words, for every second that passes your PCM wants your injector to be open 1.2 seconds -- big trouble there...

All of this assumes you are running the stock fuel pressure regulator and 58psi (stock) fuel pressure. Up the pressure and things change.

Okay... what to do: You are on the outside envelope of 60s at the stock fuel pressure. A lot of guys will tell you to turn up the fuel pressure, and that will work, but there's an easier option -- get some 75s and a peak and hold injector driver -- it will be easier to tune, drive better at low throttle, etc. That's what I'm running (and I probably should have done 95s...)

On the fuel pumps, you need more volume, flat out. The best way to do this is with two Walbro GSS340s (255lph) pumps in the tank. Wire the ground to a relay that is switched by a hobbs switch at whatever psi you what (I'd say 7.5ish) and retune.

Meth will help make up for some fuel system weakenesses, but it won't cover for this.

 

Yes the stock 5.3 block, 317 heads, is holding 20 psi but I don't think it will hold for very long.

 

Thanks for chiming in turbo berserker, I would like to find info on the peak and hold drive and 75lbs injectors. Those are high or low imp injectors? where can I find info?

 

Is there anybody else dealing with these issues?

 

i do believe myself but im NA

 

In your situation, your really not taxing the stock pump being NA, so if you wanted to upgrade, I would probably just add a inline, would be easiest and retain the function of the stock fuel bucket.

 

Erik, the point I was trying to make was that a stock pump is rated at about 160lph @ 58 psi. If you are running another pump, in series, like an in-line 255lph pump, now the in-tank pump only has to supply fuel to say 25 psi which would let it flow something like 275lps at this lower pressure. Then the in-line picks up the other 33 psi which it is capable of flowing something like 350+lph at that pressure. I'm kind of pulling these numbers out of my butt, the pressure to flow ratings are probably a bit different, but I'm just trying to show the theory behind my thinking. But like you say the in-line can only flow what the in-tank will free flow with no pressure (which is more then the 58psi rated 160-170lph). But I still believe that an in-line with a stock intake will flow more volume then just a single intank 255.

Of course the only real way of knowing what is going on would be to run a fuel pressure gauge and a scanner.

 

I was reading another mag this morning on the pot again... GM high tech, (march 06 volume 12) they had a gto with a built 5.7 9:1 comp with heads and a way bigger cam than I have and he was only running 42lb injectors and the stock pump with msd boost a pump making 670hp and 694lbs rear wheal at 10psi... How the hell is he doing that he is pushing way more air than I am, with that displacement, afr heads and cam. He also runs 15psi at the track. I know he has a returnless system, but it can't be that big of a difference! Can it?