Quote:
Originally Posted by Benyen Soljax  
too many assumptions, too little science.
have you ever ridden in 6th gear? you dont have to be using "high rpms" to go slower. i can go 25 and be in 5th or 6th just fine. im betting im going to use less gas than you going faster and using "lower rpms". id put a mortgage on it if i had one. |
Quote:
Originally Posted by tsanto I'll get carried away i guess:
Basic thermal eff.
Nth= Wout / Qin
Where Nth= engine efficiency Wout= energy from force out
Qin= energy in (fuel)
Basic translation is Efficiency equals the % of heat transformed into work (energy).
Engine eff. is roughly 25% due to losses in the engine (engine heat, friction, work used to turn engine equipment)
This simply means that out of 100% energy that fuel contains (Kinetic energy), only 25% is actually utilized to create work (move your car).
At high rpms your engine needs to works harder to create the same out of Wout at a lower rpm due to higher friction losses, more engine heat, etc.
Basically the total Wout will be less because your Wlost is higher at high engine speed.
Havent you seen that old school quaker state motor oil commercial with Dennis Leary?
HEAT is bad for engines, and in thermal efficiency terms you see bigger losses the harder the engine runs and the hotter it gets
Nth=Wout/Qin
When engine runs at high rpm, Wloss increase. Which means Wout is less.
For example
Nth1=Wout/Qin @ 65mph
Nth2=1/2Wout/Qin @120mph
Nth1 > Nth2 |
well that guy just did a whole shitload of science to say some of what i said, higer rpms usually means more gas. (of course 120 mph was an exaggeration...at that speed the wind resistance is extremely high)