MPG calculators

[TheEnemy]

Originally Posted by Old Tele man

...in different post, he stated the weight would be closer to 2400 lbs.

I would be impressid if the weight was below 3000, considering the vehicles I have and what they weigh. Though without having the year to go by I am guessing.

99 nissan frontier 2800lbs with aluminum 4cyl
84 Cj7 3000lbs
66 Mustang suposedly 2500lbs
05 Honda Accord 3200lbs

[gone-ot]

Originally Posted by TheEnemy

I would be impressid if the weight was below 3000, considering the vehicles I have and what they weigh. Though without having the year to go by I am guessing.

...his original posting:

Originally Posted by sgtlethargic

Yes on the racecars, no on the manuals- I'll try to find some. It's good to hear you got pretty good mileage. The Ranchero is the same weight as the Pinto (2400 lb).

[sgtlethargic]

Originally Posted by TheEnemy

Your talking about the Ford Ranchero?

Does it have an electric, clutch or direct driven flex fan?

Punching my best guess into the calculator I come up with a max of 22mpg between 35 and 45 mph. That is assuming you have a clutch fan, and a standard transmission.

weight 3500 lbs
crr .008 (a bit low I think)
Cd .45 (typical for a truck)
frontal area 20ft^2
Engine efficiency .20
Drivetrain efficiuency .85
Paracitic overhead 5000 (those fans really pull power)

Yes, a 1961 Ranchero. I'd have an electric fan, standard trans, it weighs ~2400 lb, and it's Cd is probably close to the .34 default.

Here's what I did:
Vehicle weight: 1088.6 kg / 2400 lbs
Crr: .015
Cd: .34
A: 1.9 m2 / 20 ft2
Fuel energy density (Wh/US gal.): 33557
Engine efficiency: .20
Drivetrain efficiency: .95
Parasitic overhead (Watts): 0
rho: 1.22 kg/m3

... which yields 29.4 mpg at 65 mph, and 32.6 mpg at 60 mph.

[gone-ot]

...I'd think the Cd would higher than 0.34 because of the bed area, probably closer to 0.40 or more.

[sgtlethargic]

HowStuffWorks "1960-1965 Ford Falcon Specifications"

1961 Ford Falcon (109.5-inch wheelbase)

Ranchero pickup Weight (lbs.) 2,338

[sgtlethargic]

Originally Posted by Old Tele man

...I'd think the Cd would higher than 0.34 because of the bed area, probably closer to 0.40 or more.

Probably, but I'd do something about it- like an aerodynamic shell.

[TheEnemy]

Looking at the model year, 2400lbs is probably pretty accurate, the previous and post versions (after 67) not a chance.

I agree with Oldteleman, .4 or higher for cd. You might be able to get near .35 with a good aero shell though.

Even with a good manual trans-axle you arent going to have better than a .90 drivetrain efficiency. A front engined rear drive manual should get arround .85 (15% losses).

edit: heh you were posting while I was typing.

[gone-ot]

sgtlethargic -- here's a "worked" example, that I did to check the aero-limited 124 MPH speed found by C&D and RT magazines for the Cruze LTZ, which (coincidentally!) also produced an estimated fuel economy of 32.7 MPG at 65 MPH, which is exactly what my wife has gotten twice on the same stretch of Interstate heading from Phoenix into LA (actually 32.7 and 32.6, but close enuf).

http://ecomodder.com/forum/showthrea...ion-17447.html

[sgtlethargic]

I searched "mpg estimator" instead of "mpg calculator". Here's one, but I need a guesstimate of the bsfc and drivetrain horsepower loss for a 1972 Ford 1.6 L:
Bowling's MPG Estimator

I thought I had found another one that just used engine horsepower.

[gone-ot]

...yep, that's another one, but there are two problems:

...first, we seldom know the Engine Brake Specific Fuel Consumption (BSFC: gal/hr-hp) for our engines; in fact, this is one parameter that we're usually actually LOOKING for most of the time. If you have a BSFC chart for your engines, consider yourself VERY lucky!

...second, we also don't know what the actual Driveline Horsepower (HP) losses are, although the commonly used values of 10-15% for manual transmission and 15%-20% for automatics are pretty close; with FWD being slightly worse than RWD.

...also, I have no idea why he asks for tire pressure (PSI), since it's NOT used in any of the equations he shows.

...a good "Rule-of-Thumb" to remember: at about 50-55 MPH, the roadload (Roll: drivetrain + tires) loss typically "equals" the aerodymanic (Aero) loss.