What is your GPH at WOT with your engine?

[Silvertip]

Re: What is your GPH at WOT with your engine?

On your V8 Chrysler, if 500 extra RPM bumps fuel consumption by 2 gallons/hr, going from 3000 to 4400 (say 4500 to keep it simple) would raise the rate to 16 gal/hr (if things were linear which they aren't). Those last 1500 RPM are the thirstiest so a figure closer to 20 gal/hr or more would be realistic. While we have no exact figures to go by other than what you tell us, the formula for two and four stroke outboards will also work for your V8 although in this example the formula would show 27.5 gal/hr vs your numbers and my extrapolation which says 20 gal/hr.

 

[dicktaber]

Re: What is your GPH at WOT with your engine?

The "rule of thumb" formula I was taught many years ago was 1/2 lb/hr/HP. For your 275 HP motor, 275 / 2 = 137.5 (pounds per hour).<br />137.5 pounds divided by 6.5 (weight of one gallon of fuel, approximate) equals 21.15 gallons per hour. <br /><br />Individual engine designs will have a bit of variation above or below the .5 lb/hr (also known as specific fuel consumption) with a more modern, more efficient engine having a slightly lower number and an older/less efficient design being a higher number, but I have seen .47-.53.<br /><br /> This works well for normally-aspirated as well as supercharged piston engines of two- and four-stroke design, and reasonably well for turbine powered aircraft as well (although measuring "horsepower" on a jet engine requires converting from thrust to HP; the generally accepted conversion factor is 2.5 lbs thrust equals one HP). <br /><br />This also works reasonably well at less-than-WOT conditions, as long as the engine is working hard enough to be efficient (for most, about 50% of max output on up).

 

[Fastjeff]

Re: What is your GPH at WOT with your engine?

Upinsmoke wrote:<br /><br />"On your V8 Chrysler, if 500 extra RPM bumps fuel consumption by 2 gallons/hr, going from 3000 to 4400 (say 4500 to keep it simple) would raise the rate to 16 gal/hr (if things were linear which they aren't). Those last 1500 RPM are the thirstiest so a figure closer to 20 gal/hr or more would be realistic."<br /><br /><br />Correct! I never hold the throttles open for more than a few seconds, and only once a year to check the WOT rpms, but I recall the FloScan going into the 20 GPH region.<br /><br />Good job!<br /><br />Jeff