On Sun, 7 May 1995, Terry McKitrick wrote:
> I am driving a 1960 Series I with a 1592 engine, 3.89 rear end, and a late
> series (25 spline) overdrive. The speedo and electrics for the overdrive
> are not hooked up yet. I am running standard 13 inch tires.
>
> I can accellerate to 4800 r.p.m. in top gear (good accelleration up to
> then), at which point it will go no faster. I can maintain this speed with
> only an inch or so of throttle depressed, and mashing the pedal to the
> floor makes no difference. I am assuming that 4800 r.p.m. is the maximum
> the car is capable of in top gear, due to wind resistance, etc. According
> to my owner's manual, 4800 r.p.m. is equivalent to about 83 m.p.h.
>
> I have the following questions:
> Assuming I can get the same 4800 r.p.m. in top overdrive, how fast will I
> be going?
It's not as simple as that. If it were, you could become a land speed
record contender just by gearing your Alpine high enough. If 4800 rpm
truly represents as much as you can do in high (assuming your tach is
accurate and all that) then you have reached a state where the hp
required to push your car through the air and overcome rolling friction
equals the power output of the car. You may go faster or slower in OD
top, depending on the speed where the power dissipated moving the car
equals the power the engine produces. If 4800 rpm is peak power, then OD
will reduce the power output by lowering the engine speed below the rpm
that develops peak power. In that case, you will not be able to go as
fast in OD as you could in direct. If 4800 were past peak (suppose peak
was 4200), then OD might increase top speed.
WRG
W. R. Gibbons Dept. of Molecular Physiology & Biophysics
Univ. of Vermont College of Medicine, Burlington, VT
gibbons(at)northpole.med.uvm.edu (802) 656-8629
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