which would use more gas?

[stealth1281]

This is a hypothetical question... Which would use more gas:

half throttle at 5K rpms, or
full throttle at 2K rpms?

I can never get a straight answer.

[Flowbee V6]

If distance isnt an issue, full throttle at 2k

[TheGreenPunisher]

This can be solved mathematically fairly simply. Ill use this example, even though its not technically correct, you will see how it relates.

Lets say that for each revolution, the engine use 1mL of gas at WOT.

Half throttle at 5K rpms would mean
.5 x 5000 = 2500mL in a minutes' time


Full throttle at 2K rpms would mean
1 x 2000 = 2000mL in a minutes' time

The result....half throttle at 5K uses more.

Torque and horsepower curves do not matter here. Only acceleration factors would require the use of torque and HP curves.

The above is the relation under the condition that the RPM's are constantly maintained.

[stealth1281]

Originally posted by Flowbee V6:
If distance isnt an issue, full throttle at 2k

what does distance have to do with anything?

[stealth1281]

Originally posted by Flowbee V6:
If distance isnt an issue, full throttle at 2k

what does distance have to do with anything?

[95Batmobile]

Originally posted by stealth1281:
</font><blockquote>quote:</font><hr />Originally posted by Flowbee V6:
If distance isnt an issue, full throttle at 2k

what does distance have to do with anything? </font>[/QUOTE]Would you drive 100 miles at 5k rpm?

[L32Projekt]

If I were trying to kill the car... yes.

[stealth1281]

yeah, you guys are right about the distance....when I was asking this, I wasn't thinking about distance.

[stealth1281]

Originally posted by TheGreenPunisher:
This can be solved mathematically fairly simply. Ill use this example, even though its not technically correct, you will see how it relates.

Lets say that for each revolution, the engine use 1mL of gas at WOT.

Half throttle at 5K rpms would mean
.5 x 5000 = 2500mL in a minutes' time


Full throttle at 2K rpms would mean
1 x 2000 = 2000mL in a minutes' time

The result....half throttle at 5K uses more.

Torque and horsepower curves do not matter here. Only acceleration factors would require the use of torque and HP curves.

The above is the relation under the condition that the RPM's are constantly maintained.

so, according to the formula, if I'm going downhill at 5K rmps (hypothetically of course) giving no throttle at all, i'm not using any gas? I'm not trying to be an *** or anything; just curious.

[98Camaro3.8]

Originally posted by stealth1281:
so, according to the formula, if I'm going downhill at 5K rmps (hypothetically of course) giving no throttle at all, i'm not using any gas? I'm not trying to be an *** or anything; just curious.

DFCO: Deceleration Fuel Cutoff [img]tongue.gif[/img]

[12secondv6]

Dunno.... why would you try to do either?

[shenanigans]

lower reves better.

[zlexiss]

Ah, but keep in mind that at half throttle, the intake manifold is under more vacuum - so the cylinders are getting a smaller mass of air on the intake stroke, and therefore will be using less fuel to keep the air/fuel ratio constant.

Originally posted by TheGreenPunisher:
This can be solved mathematically fairly simply. Ill use this example, even though its not technically correct, you will see how it relates.

Lets say that for each revolution, the engine use 1mL of gas at WOT.

Half throttle at 5K rpms would mean
.5 x 5000 = 2500mL in a minutes' time


Full throttle at 2K rpms would mean
1 x 2000 = 2000mL in a minutes' time

The result....half throttle at 5K uses more.

Torque and horsepower curves do not matter here. Only acceleration factors would require the use of torque and HP curves.

The above is the relation under the condition that the RPM's are constantly maintained.

[SpeedingFirebird]

My Bimmer has an "instaneous" gas usage gauge. At any point in time, I can see my instant MPG. Half throttle at 5K RPMS keeps me at 15 - 20MPG on the guage. Full throttle at any RPM buries the gauge.

Full throttle will always be pushing more gas into the motor.