RE: gearing doesnt create HP

[Thi VanAusdal <tvanausdal@xxxxxxxxxxxxx>]

> >You'll get better acceleration when you are in the same 
> gear.  But you'll get
> >worse acceleration when you are in the next higher gear 
> (since you'll have to
> >upshift sooner).  The net result on acceleration is actually 
> nil -- there is
> >no real gain.  One may have better 0-40 numbers; but the other may be
> better
> >0-50.  It all depends on where the shift points move to.
> >
> >Brian
> 
> AMEN , BRIAN 
> 
> This is another concept that many , have a hard time understanding. 
> HP/torque  creates acceleration , gearing does not create 
> hp.area under the curve.  (a little calculus)
> thats why the NASCAR guys will look at a road course and 
> agonize on what
> diff and gear box to use for the gears they will stay in 
> longest.      
>  Ideally , you would want an infinitely variable gear box, if 
> it would be possible.
> 
> Mark

This is another concept that many people have a hard time understanding.
Torque is a force vector x a radius vector.  Let's look at an
instantaneous
point of measurement, and extrapolate out to a dynamic system.

Given:
150 lb-ft torque (at 3000 rpm in, say, a stock 325i), 3.73 rear gear,
and 195/65/14 tires (which equals 11.99" ~= 12" radius).

force at tire on pavement (please ignore drivetrain loss - that cancels
out here)
(150 lb-ft/1 ft) x 3.73 = 560 lb
(150 lb-ft/1 ft) x 4.10 = 615 lb, or 10% more.

F=ma 

We know F, m is constant, F1 > F2, a1 > a2.  This will be true for all
rpms in each gear.

Brian's point about the short gear forcing a lower-roadspeed shift is
*absolutely
valid* - however it will only hold true until the taller gear car
shifts, in
which case the shorter rear gear will again be advantaged.  We're
talking
about 10% here.  How much time does it take to get from 6000 rpm to 6600
in
second gear?  The time my 4.10 car spends in third while your 3.73 is
still redlining second is smaller vs. the time I spend outrunning you in
second, third, and fourth.
Enjoy your second place trophy.  They do give second place trophies,
don't they?

Long shift lags will affect this comparison more at lower speeds. 

For those of you with no life, you can chart torque curves vs. rpms and
gear ratios
and figure out how quickly you reach each speed.  Me?  I'd rather not
prove Truth.

I've promoted rear gear swaps for better acceleration for several years.
I'm sorry
that you disregard my suggestions, I must be the idiot here.  But I
could have sworn
my '68 2002 with 4.10 gear would stomp the shit out of my friend's '69
with 3.64 "on
a road coarse, or a quarter mile."  

Quick, from what song are those lyrics?

 - Thi VanAusdal

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