Accel / 1/4MI / Everything calculator

[Indy]

I got bored one day and started to expand my gearing calculator. 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.skydrive.li ... ulator.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)

[The Dark Side of Will]

If you send me your boss's contact info, I can contact him on your behalf and let him know that you're undertasked, so you don't have to stop work on v1.2.34.1.3.67.2

[Atilla the Fun]

Does it compensate for elevation, humidity, barometric pressure, and the color of the driver's socks? Do we get to input the time it takes to shift? Is this manual trans only? And what about tire slip rather than clutch slip? Does it get more accurate if we have chassis dyno results to input?
By the way, on a less serious bent, I hope you realize that there's already a fairly good dragstrip sim program on the market. And the "Quarter Jr." program isn't too bad, either. The problem is that guys import unrealistic dyno sim results instead of real dyno results.

[Indy]

Does it compensate for elevation, humidity, barometric pressure, and the color of the driver's socks? Do we get to input the time it takes to shift? Is this manual trans only? And what about tire slip rather than clutch slip? Does it get more accurate if we have chassis dyno results to input?
By the way, on a less serious bent, I hope you realize that there's already a fairly good dragstrip sim program on the market. And the "Quarter Jr." program isn't too bad, either. The problem is that guys import unrealistic dyno sim results instead of real dyno results.

Yes, you get to input the time it takes to shift . "Shift Delay" input box on the "Gearing" sheet

Elevation, only in the drag part of the calculation. Like I mentioned above, engine power correction is still being worked on. Humidity, not yet. Tire slip isn't completed yet but I've been weighing the options of a couple different models. Obviously the portion of acceleration where available power exceeds traction is important. I don't think I would say it's manual transmission only, but the effects of a torque converter are not yet modeled. Chassis dyno results from an inertial dyno are currently preferrable because they do take into account drivetrain inertia and parasitic losses.

I was aware of the Quarter Jr program, though It's been several years since I've looked at it. It's more similar to mine than I remembered, though there is one big difference. Mine is free instead of $100-300.
Also, right now the ability of the program to output lots of data points is very good. 7000 points each with 11 values in about 3 seconds. Obviously if the modelling is flawed there's no number of data points that can compensate for that, but at least it has decent capability.

The sock correction factor has yet to be included. I'm having trouble finding a direct correlation between the observed faster times when wearing bright red socks.

[eHoward]

Any interest in switching careers to consulting?

[Fastback86]

What if your socks have stripes?

[JohnW]

Very nice! Useful for doing transmission and gear ratio comparisons. The horsepower and torque curves seem to yield more accurate results if rear wheel numbers are used.

[Indy]

Any interest in switching careers to consulting?

I was interested, but regrettably Victoria's Secret has turned down my application.

Very nice! Useful for doing transmission and gear ratio comparisons. The horsepower and torque curves seem to yield more accurate results if rear wheel numbers are used.

Thank you! See my post a couple up for the reason why RWHP seems to be more accurate. HOWEVER!!!1!uno I have updated the calculator to include a power loss factor that changes the entire power/torque curve by a simple percentage to account for inputting flywheel HP. Will upload on Monday.

Tire slip is getting better, but I have to figure out why my weight transfer portion is feeding it garbage. ETA on that...5-6 years. Check back then.

[Indy]

I've got the air pressure/temperature/humidity correction working. The power output is altered according to the SAE standard, drag is altered as well. I also have wind speed and direction factored in to drag.