Quote:
Originally Posted by kennybobby
This is silly to think that a bunch of physickists and mathemagicians can't understand the difference between energy and power?
A 3200 lb car accelerates from rest to 60 mph (88 ft/sec).
The "work" or kinetic energy is .5mv^2 = 387,200 lb-ft regardless of how long it takes to get up to that speed.
But power is the time rate of the change in work or energy, dKe/dt.
So 0 to 60 in 5 seconds = 77,440 lb-ft/sec = 140 hp
and 0 to 60 in 20 sec = 19,360 lb-ft/sec = 35 hp.
How much more fuel does it take for your engine to make 35 hp versus 140 hp?
Look at the dyno data--the torque-speed curve and the volumetric efficiency-fuel consumption curve to find the actual number, but it will be at least a factor of 4.
BTW this is why stop and go traffic kills mileage--it takes so much more power to get up to speed than to just maintain a constant speed.
In this case if your mileage gauge normally reads ~40 mpg for the slow acceleration, then it will drop to ~10 mpg for the faster accel.
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35hp average is a pretty low number for a 3200lb car. Typical cars are geared so that cruising on the highway is less efficient than wide open throttle 100% load acceleration, at very high rpms they're about even.