送交者: PhonyDoctorPhD 于 2005-10-13, 18:00:27:
回答: If two drives hybrid on a highway 由 HunHunSheng 于 2005-10-13, 16:32:18:
Motor does not come into play for you are going
straight at constant speed, there is no charging.
The higher your speed, the higher the resistance
generated by going against the head wind. But
unless you are driving a 60s convertabile, it is
not likely that your Cd factor will become
the dominant factor.
This said, the higher your speed,
the higher your engine must rev. You can derive the
RPM from the speed, factoring in wheel size, gear
ratio, etc. Suffice to say, it is almost linear:
higher the speed, higher engine RPM.
How does RPM related to gas consumptions? Well,
all modern engines are designed to perform in 2
kind of situation:
1) pick up, at low RPM, generate as much *torque*
as possible for acceleration;
2) high speed, at high RPM, generate a constant
*torque* but try to keep up with the speed of
the car. Roughly, torque * RPM * a constant is
the HORSE POWER, the holy grail of cars these days
Now, if you keep the RPM too low ( 6000 RPM)), you are
pushing your engine to keep up with the speed of
your car, so it breath a huge deep breath everytime.
It also waste gas cause your engine is
lacking and trying to keep up.
As you can see, there must be a mid-point where
gas consumption is most optimal. And experiments
have shown that, for most modern engine, in normal
situation, that speed is around 55mph.