MPG calculators

[sgtlethargic]

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?

[gone-ot]

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

[sgtlethargic]

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

Thanks

[gone-ot]

...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.

[sgtlethargic]

Originally Posted by Old Tele man

...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

[TheEnemy]

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.

[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)

[sgtlethargic]

Originally Posted by TheEnemy

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.

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

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

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.

[gone-ot]

...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.

[Frank Lee]

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).