MPG calculators
 

I've seen the Ecomodder one, but it doesn't have anything about what size engine, which doesn't make sense to me. What ones are recommended that have engines?

...re: ScanGauge II™, you enter the engine size in liters (ie: 305 cid = 5.0 liters) as one of the initial "setup" steps.

I'm talking Internet links, not in-car.

Thanks

...like the one here, under Tools?

...it doesn't need engine size because it's working backward from combined aerodynamic and rolling resistance loads to estimate needed HP, and then equates that to the usable power available from gasoline.

Yes, and yes I understand what it's calculating. The thing I don't get is what if it was a 454 ci versus a 98 ci engine doing the work?

And, here's what I'm trying to get at:
I put in the number guesstimates for the Ranchero and get 32 mpg @ 65 mph, 36 mpg @ 60 mph, etc. How "real world" are these figures? If I could get ~40 mpg out of the Ranchero at freeway speeds, I'd do it. If that's not likely, I'll go with the lightweight, more aerodynamic single-seater version and hope to get ~60 mpg.

Thanks

You would adjust the engine efficiency for the range you would be running the engine in.

A larger engine would be less efficient at the same power load as a smaller engine.

Add to that no two engines are the same even if they are the same displacement, year, options...etc.

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)

Okay, so how does one go about estimating the efficiencies of different engines?

It's an estimator, so that seems like splitting hairs.

>>>

The point being, I can't find the MPG estimator I used the other day.

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

...and, transmission GEARING and AXLE make a huge differential; geared one way, the engine could make almost full HP at highway speeds but get lousey milage; geared differently, it could just barely exceed the HP needed at highway speed and get great milage, but couldn't pull a sick Grandma off her rocking chair if she was dead.

Remember the estimator gives good numbers for steady state, level, no wind cruise. Add the real world- stops and starts, grades, winds, etc. and one should knock at least 10% off the estimator's cruise value for what you'll realistically get (excluding P&G and whatnot).

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

...his original posting:

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.

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

HowStuffWorks "1960-1965 Ford Falcon Specifications"

1961 Ford Falcon (109.5-inch wheelbase)

Ranchero pickup Weight (lbs.) 2,338

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

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.

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

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.

...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.

I don't think the driveline losses are quite that bad. But FWD is BETTER than RWD as hypoid gears- as found in rear axles- have a bigger sliding component to the gear mesh vs FWD diff gears.