jorj7

Tuomo,

I have two problems, one is losing fuel pressure under peak load, and the other is
hot fuel. A larger pump may solve one, but it makes the other more extreme. I didn't
have the overheated fuel problem until I went to a larger fuel pump... The Bosch 044
pump didn't overheat, but it couldn't pump enough when I got to 500+ rwhp. The Fuelab
could pump enough but would overheat and start to cavitate. The Aeromotive is in the
middle as far as volume per hour per psi, but it also overheats, then can't maintain the
flow. You are right though, I should be getting more fuel pressure as the boost increase,
which isn't happening in the dyno runs. I have tried the Mityvac on the regulator before, but
not on this one. I'll have to try it again, though I don't have much time since we are leaving
in the morning.

Here's a comparison I did of the different fuel pumps:

IcemanG17

Georges issues are puzzling.....it appears he has plenty of fuel flow for his HP...even at higher BSFC #'s than he needs.....but still issues? Very odd indeed.... However I am confident it can be solved....

IcemanG17

Hmm.....what about a combo of pumps...maybe an 044 and something larger...so the 044 acts like the in tank pump and the larger pump the primary pump on stock 928's......

What does John Kuhn run in his? However he is not holding WOT for very long either which changes things dramatically

Bill Ball

The problem is this issue has not changed much despite different pumps, different FPRs, moving the Aeromotive to in-tank (right at the bottom), and increasing the fuel delivery and return line capacity. Right now there is nothing upstream of the pump except perhaps an Aeromotive filter. Fuel consumption may be high, but I don't think we are less than 2MPG which it would have to be to exceed the pump rating.

Z

Sufficient voltage and current getting to the pump(s)?

jorj7

Z,

That's another thing I check while on the dyno. I checked the voltage acrossed the
leads going to the pump and I saw 12.5 volts at over 5000 RPM. The pump controller
was sending 8.5 volts at idle and increased with RPM. The controller has power directly
from the battery positive terminal, the positive lead from the fuel pump relay, and a
tech signal from the kick down relay pin 31b (like in your email). I didn't check the
amperage, as I didn't have my good DMM with me...



I also tried it with the override switch set on the fuel pump controller, and that didn't change
the fuel pressure issue.

jorj7

Brian,

For my target hp I think would need about 74 gal/hr flow at 65 psi fuel pressure with
15 psi boost (based on 50 psi at 0 inch vacuum). That's below the 85 gal/hr
rating of the Aeromotive, but above the rating of the Bosch 044. As it is, I'm well
below that. From what I can tell, I was hitting about 60 gal/hr at the last dyno
run. Heck for the power I was getting I could put back the 044 and stop the over
heated gas problem... But I'd really like to get closer to my power goal without the
overheated fuel.

John Speake

IIRC Loiuie is using a single 044 in his stroker which makes nearly 600rwhp, so there's something badly wrong is your setup....

ptuomov

Without the alcohol spray, Ott made maybe 570 rwhp. I amguessing his AFR is about 13.5. The supercharged car will run about 11.5 to limit knock. Then, there's about 15% power loss from turning the supercharger. So the required fuel flow to generate 570 rwhp with a supercharger is almost 40% higher.

John Speake

George spoke about "500+" so I assumed not much more than 500rwhp.... Louie was in the high 500's.

What fuel system is Mike Simard using with his monster stoker ?

ptuomov

I think that given the possible pressure losses in the fuel piping and other such issue, 85 vs. 74 gal/hr is very narrow margin. Especially since the Aeromotive pumps have a reputation of being flaky pumping against higher pressures.

If I understood you correctly, when you tried your dual 044's, you didn't have a pump controller. Now you do. So how about installing the dual 044's inside the tank and running them with the controller?

Also, what's really the problem with fuel temperatures going up by 20 degrees or so? I understand that high altitude and hot fuel were a problematic condition when you had an external pump because the external pump is setups are prone to cavitation. But now that you have an internal pump, isn't that risk hugely reduced and fuel temperature less relevant?

Lizard928

The Bosch 044 pump is good until 600 RWHP naturally aspirated or 500 RWHP with forced induction. It has to do with the extra enrichment that the boosted cars need.

ptuomov

The wedge is bigger because the supercharger uses a huge number of ponies to drive it. This morning before work, I quickly computed 38% more fuel needed for a supercharged car running max power under the knock limit relative to a naturally aspirated car that is not knock limited.

AO

I think you're quite a bit high on that. Of course a lot depends on SCer efficiancy.

I have a spreadsheet somewhere with all the calculations, if I can find it.

ptuomov

I recall I assumed 15% of the gross hp before supercharger being consumed by the supercharger and knock limited optimal AFR of 11.5 vs knock unlimited optimal AFR of 13.5. Those lead to slightly under 40% more fuel. In addition, if the pressure differential between the manifold and the fuel rail is to be kept constant, the pump will have to be able to deliver this extra fuel flow against higher pressure.

The popularly quoted number, such as BSFC as low as 0.40 for N/A knock unlimited and as high as 0.65 for supercharged knock limited engines, aren't far from that.