I originally wrote a calculator back in the 80's when I was autocrossing and fitting different size tires while driving the car on the street. This was a PC-DOS application that printed out a chart of MPH for each 200 RPM between 1000 and 8000. This app also allowed you to enter your torque curve (stock curves were available in the owner's manuals of the time) and the program would calculate optimum shift points, and, if you entered the car's cross-section (amount of square feet presented to the oncoming air and also given in the owner's manual), it would even calculate your theoretical top speed.

I then rewrote it in Java as an exercise in learning that language, and so it would be accessible on a web page. I never included the shift point and top speed calculations in the web-based app. Now, of course, Java apps are either forbidden (Chrome) or tough to get to run, so I needed something else to use, and to possibly share with other enthusiasts.

Here's my first attempt at a working app:

Gear Charting Application

For now, if you don't have a 914-4 or 914-6, you'll have to enter the Porsche gear sets manually, as they're not included in the selection listing. I hope to add many other Porsches as standard selections in the future. If you have a suggestion, especially on common standard gearsets, PM or email me. Also, let me know of problems you might encounter. The "Help" button will bring up a fairly detailed explanation of the program.

This app is written to be "mobile-friendly" so it will look fine on a smartphone or tablet.

Now that is a great app! I've been thinking about the gearing for my 914-6. This answers a lot of questions for me.

One thing I notice though. The 914/4 and 914/6 have the same A gear ratio of 11:34. When I selected the 914/6 gears, you have 18:34 for 1st. The 914/4 gears setting is the correct 11:34 for 1st. All of the other gear ratios you use for 4 and 6 are correct.

Works great in chrome thanks

Not so good in Safari, never opens the additional tab, setting allow for tab opening. Not an issue just a minor bug if you care.

Thank you again for doing this

Thanks for catching that! It's been fixed.

I don't have access to Safari, so I can't really troubleshoot it from here. While the method I used to request the browser to open a new window or tab is supposed to be supported in Safari, I've changed the code to use a newer method that still seems to work in Chrome and Firefox. Give it a try and let me know if that works in Safari now.

Working great now

Thanks for your help. I've also updated it to provide for inputting the torque curve to calculate optimal shift points. Read the help file for an explanation. You can see a sample chart with shift point calculation by selecting "1975-76 914 2.0L 5-speed (with torque curve)" from the gear selection list.

Interestingly, you don't want to go anywhere near the redline on the 75-76 2.0 for best acceleration. Hopefully, I'll get a chance to confirm that with some real-world data.