No need to go no the Internet and have a website with advertisements and Javascript for a simple formula that you can write down. Any high school scientific calculator can do this without the need to do the order of operations by hand. The first formula for wheel circumference: Where W D and R cor…

[image] TheWonderful90s: Example: 195/70 r14 tire is (195 x 70 / 1270 + 14) 3.14 = 70.7 inch circumference. That should be 77.7 inches. A fat-fingered mistake I’d guess. Looking up revs/mile for that size tire on Tire Rack Specs, you get 839 revs/mile for a 24.7 tall tire in the size you cho…

[image] VOLVO-V70: Shouldn’t wind speed and direction plus distance above sea level be included in this silly exercise. And payload, driver input as far as acceleration and braking, tire rolling resistance, pavement surface, rain or shine, parasitic engine loss from electrical loads like defr…

I have never felt the need to calculate engine RPM, but then I do not do cryptograms, wordle, or math exercises. I think about other things, like why hasn’t Wile E Coyote ever caught the Roadrunner or why isn’t it obvious to Lois that Clark Kent is Superman?

Fuel mileage is not just a factor of engine rpm. Rolling friction matters a bit, aerodynamic effects dominate above about 40 mph. Aero is a factor of frontal area, the coefficient of drag and speed. Drag = 1/2* air density * frontal area * speed^2 * drag coefficient Twice the speed creates 4 time…

[image] Mustangman: Twice the speed creates 4 times the drag. It’s 8 times the drag, but 4 times the energy used, since you get there in half the time, half as much of the 8 times as much energy is needed. I think when I’m going 52 MPH, at least half of my engine’s fuel is used to keep the e…

[image] TheWonderful90s: It’s 8 times the drag, Do you see a cubic function there? No. Drag is a square function. Horsepower to reach that speed or maximum speed is a cubic function.

[image] Purebred: why hasn’t Wile E Coyote ever caught the Roadrunner I live in Albuquerque, where roadrunners are common. I’ve nearly run them over on my bicycle: they aren’t that fast. You can find real encounters between the 2 on YouTube: guess who wins.

[image] Mustangman: Do you see a cubic function there? No. Drag is a square function. So drag must mean the force that must be overcome to move through the air. 8 times the energy is needed to go twice as fast, the force pushing against is 4 times.

[image] TheWonderful90s: 8 times the energy is needed to go twice as fast, the force pushing against is 4 times. Drag is a force. Energy is the fuel in the tank waiting to be used. Power is the rate of use of that energy. That is a cubic function with respect to aero drag. Power to push the …

Formula to calculate engine RPM from speed, tire size, gear ratio, final drive, and estimate fuel economy

Power/Fuel

VDCdriver May 10, 2025, 12:45pm 6

… or why did Clark never get into trouble with the cops when he used outdoor telephone booths to change into his Superman costume?

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Formula to calculate engine RPM from speed, tire size, gear ratio, final drive, and estimate fuel economy

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