So, how much fuel is really required to feed a 750hp 540? People are always talking about these killer "million gallons per hr" fuel pumps, "sewer pipe size" fuel lines, etc, but nobody actually seems to design/calculate what is really needed. People always seem to do, well, what everyone else does, or maybe what some tech line guy tells them. The problem is, there was no engineer in sight, to actually figure out what is necessary. So, let's do a sanity check and take a look at what is really needed. Consider the real world numbers below.

Here's some data I've gathered up:

625hp Bill Mitchell 540, consumed fuel at a rate of 49 gal/hr at WFO throttle on the dyno

722hp Beck Racing Engines 540, consumed 50.3 gal/hr

890hp buddy of mine's 540, consumed 56.7 gal/hr

This is a reasonable cross section of the very popular 540's. This group averages out to 746hp with an average fuel consumption rate of 52 gal/hr, where the BSFC = .42 lbs fuel/hp hr, and keep in mind that these are real world actual numbers. So, much for the text book number of BSFC = .5 lbs fuel/hp hr, that people so often quote, which is off by whopping 16%. We've looked at what these engines want, now let's look at what it takes to give them what they want.

Consider a tank with fuel 6" deep. If that tank has only a 3/8" hole in the bottom, it will gravity feed at a rate of 1.8 gal/min or 108 gal/hr. Which is more than double what those 540's want. At that rate, a 16 gal tank would run dry in about 8.9 minutes. But with a 750hp 540 sucking on that tank at a rate of only about 52 gal/hr, it would take about twice as long to empty the tank, which wouldn't run dry for about 18 minutes. Even considering factory 3/8" hardline frictional losses, the flow rate up at the engine is still WAY WAY more than that 540 could ever want. In addition to that, a 14 psi mechanical fuel pump, free flow rated at twice the engine's actual consumption rate, and regulated to 7 or 8 psi, can also feed all the fuel the 540 can drink. And that 14 psi spring/diaphram assy in the fuel pump, can suck on the fuel line plenty hard enough to deal with all the launch G-Forces that the 540 could generate in an average weight hotrod. So, why again do people NEED those "million gallon per hr" fuel pumps and "sewer pipe size" fuel lines? Something to think about the next time you feel the need "overkill" your fuel system. There's nothing wrong with overkill here, but it just isn't needed.

If you are running a car that leaves hard it can take a good pump to overcome the force of acceleration depending on where the pump and tank are located. I used a BG 280 for my 572 and two stages of gas. But the pump and tank were mounted in front of the motor.

Let's take another look at the 3 original engines in this post, you'll recall that all three are 540's, but:

………..HP………………………….....……........gal/hr…………………………...….....…...….BSFC lbs fuel/hp hr (fuel burn efficiency)

#1…….625…………….…………......….…...……..49……………………………... .…….............47

#2…….722 (up 15.5%)………….……....….…..50.3 (up 2.7%)..…………….……..…......42 (improved by 10.6%)

#3…….890 (up by 42.4% over # 1)………….56.7 (up by 15.7% over # 1)………….38 (improved by 19.1% over # 1)

You can see that it takes more fuel to make more hp. Afterall, only one things makes hp, and that's burning fuel. Everything gearheads/builders/racers do in the pursuit of more hp, is in support of burning more fuel and/or burning that fuel more effeciently. Some might find it interesting that, by looking at the BSFC, the engines get much more efficient as the hp goes up. That might be the opposite of what some people would expect, right off the tops of their heads. Even though the most powerful engine takes more absolute fuel to make that extra power, it only uses .38 lbs of fuel per hp hr, or 19.1% less to do that, than the weakest engine, which takes .47 lbs of fuel per hp hr, to make less power. So, who says there is no free lunch? :-)

You should always go overkill, if down the road like everyone else in the world you decide you want more power... you will not have to waste money on "another" fuel system.