Jim,
Thanks for the empirical formulae Jim. I had the one for HP versus 1/4 mi
speed, but not the others. What does the HP versus rpm curve of your motor
look like? To get the most out of the motor, of course you want to operate
it in the sweet spot; i.e., rpms spanning the HP peak. If you top out at
the end of the 1/4 mi at 5500 rpm, this would imply that your peak HP is
down around 5000 or less. I'd be surprised if this were true for your 351C
motor. Isn't your peak HP up in the 6-7000 rpm range? And I believe you
want to be crossing the lights wound up past the HP peak, at the point you
would just be ready to shift again. The goal is to get the maximum
integrated horsepower out of your motor over the whole 1/4 mile, although
your ET depends relatively more on what happens early in the run.
Bob
At 05:37 PM 3/28/99 -0500, you wrote:
>At 09:51 AM 3/27/99 -0800, you wrote:
>>Jim,
>...
>>BTW, I'm surprised you are still running the 2.88s, especially with the new
>>overdrive tranny. Have plans for a new rear end with a limited slip??
>..
>>Bob
> I have mixed feelings about the overdrive transmission.
>The low gear is 3.29 to 1. That seems to be way too low for
>a high tork 351C in a lightweight Tiger. I just barely get started
>before I have to shift to 2nd. However the numbers below seem to
>indicate this is close to correct. 2nd gear at 1.84 is a big drop
>from 3.29, Third is 1:1 . OD is 0.81
>
>The following general equations may help explain why I am still using a 2.88.
>Note * indicates multiply.
>
>MPH in 1/4 mile= 10+(221 * Cube root(HP/ weight with driver in pounds)
>Example: 350 HP, 2600 lbs gives 123.26 MPH.
>
>Required Rear end Ratio= (RPM * Tire Diameterinch)/(310 * MPH)
>Example: 5500 RPM, 21" tire @ 123.26 MPH gives 3.022 rear.
>
>Optimum First gear Ratio= (Tire Widthinch * MPH)/HP for manual transmission
>Example: 9" wide tire, 123.26 MPH, 350 HP gives 3.169 low gear.
>
>Optimum First gear Ratio= (Tire Width * MPH)/(1.8* HP) for automatic
>transmission
>Example: None
>James Barrett Tiger II 351C and others
>
>
Robert L. Palmer
Dept. of AMES, Univ. of Calif., San Diego
rpalmer@ames.ucsd.edu
rpalmer@cts.com
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