Inliners International Forums General Discussion Tech Tips Fuel flow requirements

Too often people spend way too much on fuel pumps. Instead of buying what they need they read the advertisements and figure bigger is better. While this rule may apply to male anatomy it doesn't apply when shoping for a fuel pump.

Roughly figure the engines horsepower then divide that figure by 8. That will tell you how many gallons per hour your engine requires to make full power and includes a 50% safety factor. This is based on a BSFC of .5 for naturally asperated engines.

Example: 400 HP divided by 8= 50 gallons per hour. A 50 gph fuel pump will supply 50% more fuel than the 400 hp engine requires.

Be careful not to use any 90 degree brass bends in the fuel lines as these are too restrictive and can cause trouble. ALL brass fittings should be inspected to make sure the inside hole is large enough for the engine's fuel requirements.

Ron

All these numbers are correct. But when it comes to holding the throttle wide open 5 miles, a 5/8" line to a 110 pump feeding a -8 line to 2 -6's makes me feel a lot better. Remember that a dash 6 line is advertised as a 3/8" but is a lot cloesr to 5/16" when measured..................Good Luck. thanks Ron

I agree - buying a big pump is a common error but harmless (except for the $$$!).
Figuring out the line sizes and choosing the fittings is much more difficult, frequently done wrong (1 90° plumbing fitting ruins the whole thing). I've seen many serious cars with "just that one" fitting re-used from the old system, and it was too small.
Also forgotten: a comparison of line size is somewhat misleading. The 5/16" steel line from the tank with a big mechanical pump won't handle more than perhaps 400 HP, but the same line fed by a high-press FI electric pump at 45 psi doubles the flow rate, you just have to regulate it down at the fuel block.