Will a car at 3,000 RPM at 50 MPH get half the mileage of the same car at 3,000 RPM at 100 MPH?

[Rafs-T-Type]

All other things the same, except wind resistance will obviously increase. Also does engine management make a difference i.e. MAF vs. speed density.

 

[bison]

Not even close. Rpm doesn't determine fuel consumption. Engine efficiency and rolling resistance do. You can use an accelerometer to measure g force at different speeds. If you're at -.13 with no throttle at 100mph and -.06 at 50 you will need a lot more road horsepower at 100mph to maintain speed. The extra speed doesn't offset the resistance. It might take 12hp to maintain 50mph but 35hp to maintain 100mph. So you would be using about 3x the fuel but only traveling twice the speed.

 

[Rafs-T-Type]

What if the cars had the same engine and the 50 mph was in a lower gear?

 

[Chuck Leeper]

Pay a visit here... Maybe you'll get an understanding of some of what's involved....

http://phors.locost7.info/phors06.htm

Or, find a copy of the Chevrolet Power Manual...LOTS of math there....

 

[Rafs-T-Type]

Someone put it in simple terms for me that made sense..."It's not rpms that dictate fuel consumption, it's throttle position".

 

[Red C5]

Seems like it would be pretty easy to test this. I'll let you know on my next drive to Vegas.

 

[charlief1]

As bison said. "theoretically" the HP lever with all things being equl, you'd need X horse power/torque to go at 50 MPH and it would increase exponetially at 100 MPH. So if it took 50 HP to maitain a 50 MPH speed then you'd need 150 HP (roughly) to maintain 100 MPH. You'd need to calculate the drag coeffecient at both speeds and that will change as you increase speed partially because of the mass of the vehicle, type of tires, wind speed/conditions, ect. This isn't exactly an easy answer.

 

[TurboTnZ06]

I'll have to go calculate it up. I know I went 3 hrs in my Z06 avg 101 mph (Kansas is a boring drive). I got about 20-22mpg IIRC (this was like 10yrs ago). I'll have to go see the same rpm in some gear around 50 mph at lunch to get a comparable number...

 

[pacecarta]

Someone put it in simple terms for me that made sense..."It's not rpms that dictate fuel consumption, it's throttle position".

simple physics
... its load that increases and needs more hp (fuel and air ) . the tps will need to be opened more to acheive the hp required at 100 vs 50
3000rpm pushing a vehicle that has low drag at 50 will take lets say 38 hp because the speed is low drag is low at 3000 gearing must be high numerically (approx 4.20s in D with 26in tire ).. less load engine needs less hp to move the vehicle
now his scenario was same 3000 but at 100 mph so the drive final gearing has changed (lower numerically which and his example means gearing has to drop in half we are talking about a drive ratio of ~2.20 in D with a 26in tire and it will mean more hp will be required to push said vehicle ... to make more hp you need not only more fuel but also more air so you will have to open the throttle more , but if the throttle is already wide open and you cant get enough air at 3000rpm to burn the required fuel you wont make the hp to pull the load..
frontal wind resistance makes a vehicle feel like its going up a hill and theres also downforce that makes the vehicle heavier

 

[bison]

I'll have to go calculate it up. I know I went 3 hrs in my Z06 avg 101 mph (Kansas is a boring drive). I got about 20-22mpg IIRC (this was like 10yrs ago). I'll have to go see the same rpm in some gear around 50 mph at lunch to get a comparable number...

A z06 has minimal drag compared to a g body even at high speeds. 22mpg@100mph. That's nice. Check deceleration in neutral with an accelerometer in a z06 and then a g body. The
G body is a flying brick. About 10mpg@100mph

 

[Paul69camaro]

Below is the drag equation, I copied it from wikipedia. As you can see that velocity is squared so the drag or force pushing against the car goes up by a factor of 4 when you double speed. This is just one factor of the overall equation, rolling resistance from your tires also comes into play. You can figure out the resistive forces and can an idea of how they change with speed. BTW, I hate you for making me regurgitated stuff from an engineering fluid dynamics class I took over 6 years ago! Drag equation:

where

is the force of drag,

is the density of the fluid (air),

is the speed of the object relative to the fluid,

is the drag coefficient (not good on a turbo buick brick)

is the reference area

 

[TurboTGuy]

All other things the same.....

14 x 44 x 1.5 x 67 plus your sisters 17th birthday date and time = the gaseous expultion rate of my backside orafice...........

Holy crap! REALLY??????

Blahbiddy blah blah blah...............

The GN/Turbo T Math Busters is a whole different board.... Go there.......

Sheesh......

- Not so much a Math Guy....

This is all meant in fun, all you Bill Nye, the Science Guy posters........

 

[EVIL]

All other things the same.....

14 x 44 x 1.5 x 67 plus your sisters 17th birthday date and time = the gaseous expultion rate of my backside orafice...........

Holy crap! REALLY??????

Blahbiddy blah blah blah...............

The GN/Turbo T Math Busters is a whole different board.... Go there.......

Sheesh......

- Not so much a Math Guy....

This is all meant in fun, all you Bill Nye, the Science Guy posters........

what if my sister is 16? Does anything change besides my uncle going to jail?

Resistance is the factor here. If this test could be done in a vacuum then i think the results would be more favorable, but not so much my uncle.

D

 

[TurboTGuy]

what if my sister is 16? Does anything change besides my uncle going to jail?

Resistance is the factor here. If this test could be done in a vacuum then i think the results would be more favorable, but not so much my uncle.

D

I AM the uncle in the vacuum.......and I must ask....why do YOU ask, twodogsgrinding?

 

[Paul69camaro]

All other things the same.....

14 x 44 x 1.5 x 67 plus your sisters 17th birthday date and time = the gaseous expultion rate of my backside orafice...........

Holy crap! REALLY??????

Blahbiddy blah blah blah...............


The GN/Turbo T Math Busters is a whole different board.... Go there.......

Sheesh......

- Not so much a Math Guy....

This is all meant in fun, all you Bill Nye, the Science Guy posters........

Ok, sorry, I thought the OP asked a technical question so I tried to answer him the best I could. I'll now try to explain it in a way an inbred can understand... The faster you go, the more fuel ( yes this means gasoline) you'll burn. So when your jailbird uncle goes twice as fast, he's fighting against 4 times the air resistance.

Paul

 

[killer231olds]

You lost me at will a car at 3000 rpm.