Some updates to the problem Red Doggie handed me.
The equation I used is from a physics book source and not a goofy automotive
chat room site.
It is dimensionally correct for aero drag force: (kg x m/s^2), so the result
should truly be in Newtons and conversion to pounds is simply N x 0.2247.
One does have to change mph into m/s so all input variables are in SI units,
BTW.
However, to clean up where I took it from there and answer all his
questions, I changed the tire radius to exactly a foot so that torque at the
axle from pounds of force at the tire patch is then is exactly in ft-lbs.
The HP would have to be 60 HP at 2100 RPM with no further gear reduction.
Or, if you perfer what would probably be a much smaller displacement motor
running at a much higher RPM, use a 4.28 final drive and spin the motor to
9000 rpm. 60 HP would yield the same required force at the tire patch.
Now, I don't know where Red Doggie got the problem parameters from, but it
could be a real world example in terms of just aero drag. The total frontal
area seems pretty small at only 0.5 m^2. And while the Cd seems rather high
at 0.6, Cd is actually not constant with speed and that might possibly be
real World too.
Other losses like drivetrain and rolling loss will probably require a bit of
additional HP or Torque to get to 150 MPH, I reckon.
So, what do my results all mean?
Not a lot, really.
Since one is mainly interested in acceleration all the time in racing except
for braking, HP has got to still be paramount since it is the rate of using
energy to accelerate a mass. In fact , I reckon one uses energy at a HP
rate even when not accelerating just to overcome drag for any length of time
for top end.
Upon reflection, I should revise some of what I said earlier about HP
restictors not being the way to go to reduce the effects of high dollar
engine builds: intake restictors really should be fairly effective.
Should you you shift at the HP peak for max acceleration and gear for the
torque peak for top end???
I don't really think so on the second part.
HP and torque are joined at the hip by a constant (5250) and RPM.
Chuck
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