I got bored one day and started to expand my gearing calculator (not sure I posted that over here). It got out of hand pretty fast. It now is basically a 1/4 mile time calculator. Basically it solves the kinematic equations for displacement, velocity, and acceleration in discrete time steps (rather than a differential equation of course), while stepping through the gears and also determing power level for a given RPM. I've been wanting to test it out with some real numbers. It still needs ALOT of work ironing some little programming kinks/bugs, linking air density to not only drag but engine power correction, rotating inertia, etc. The list is rather long...

You can download here: http://cid-c2450a443ec5760c...ion%20Calculator.xls
Right now, after entering in all of the appropriate data in yellow cells in the first three sheets, YOU HAVE TO RUN THE AccelCalc MACRO! The results sheet does not currently automatically update.
The results are given on the "Results" sheet. The header titles should be self-explanatory.

A run down on operation:
1.Computes launch at constant RPM/clutch slip/power using the procedure explained below. (the accuracy of using this model is one of my biggest concerns)

2. From your first velocity, drag, as well as the engine RPM is found

3. Linear interpolation between the relevant HP/TQ points to determine the engine output TQ at that instant

4. Engine output TQ gets multiplied by total gear reduction for that gear, combined with wheel diameter = force, or thrust

5. (Thrust-Drag )/Mass= Accel

6. The "core" equations for velocity and position are solved for a small time step (~.005 seconds)

7. New velocity => new RPM, new HP number, new TQ. Loop gets solved again until it runs to the shift-out RPM for the current gear.

At a gear change, the output TQ is zero so the only force acting on the vehicle (besides all of the mechanical resistant forces that I have yet to include %) ) is drag, so the core equations are solved again for drag acting during the time period of the shift delay.

1,320 feet later you have a whole slew of data, which I am currently working on condensing graphically.

Test, criticize, report back. (please)

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My Web page | The Turbo Super Duty Build.
You know that little voice that says it can't be done? I duct-taped its mouth shut and pushed it down a flight of stairs. (Leader of the Insurgency)

I used to have an old dos-based program called cartest that did this, and had a huge database for cars.. also did track races. I loved that software, but can't find it anymore.. This was a long time ago.. They have a new version that's pay-for, but I'm cheap..

Good luck!

Thats great. I had a copy of your gearing calculator that I messed up. Wasn't able to find it again so I'm really glad you added to it. This is one of the best. Thank you for posting.