Project RX-7

So time to start the first massive post, or series of posts. As per the title, i'll be looking at the effects of this swap on the 7.. without actually doing it. Effectively I'm going to simulate the results using a few equations and calculations i learned at school, with the help of a nifty little program called Excel Dyno.

This is a simple spreadsheet program with lots of the more common engineering formulas already embedded into it. Things like a simple distance vs time graph, as well as gradients, traction and shift points are automatically calculated based on the data supplied. So the program is only as accurate as the data that's given to it, a daunting premise given that I don't actually have a car to the record data from and the data gathered from the net has no accuracy guarantee.

Nevertheless, part 1 is dedicated to collecting said data.

If you're interested in doing this yourself to your own car, Excel Dyno is available here:
http://offroadvw.net/exceldyno/

All credit goes to Wes for this uber little big spreadsheet.


Why?

Strictly speaking there is no real reason to swap the standard gearbox for another one. The stock 5 speed is sturdy and reliable with a very pleasant shift feel. However. There are advantages to having an extra gear, the most important of which is cruising speed (engine speed) given by the last gear ratio and the final drive combined. Cars generally spend a lot of time on the freeway (or Autostrada in Italian). My 7 will be no different. I have lots of experience with 5 speed cars on the freeway, and every time i drive one, i keep asking myself if the world would be better without them. The 7 isn't a parsimonious car to start off with, so anything i can do to improve its real world performance without changing the feel of the car is absolutely worth it.
Swapping a gearbox is very expensive and time consuming. Using a simulation is the best way to actually gauge the improvement before spending valuable time and considerable money on the swap.


Which box?

 There are 3 options to choose from that have already been attempted.

Tremec competition box
Toyota Supra box
Aisin AZ6 (Honda S2000 Mazda MX-5 RX-8, Toyota Altezza box)

of these 3, the Aisin is definitely the most palatable. The Toyota box is overkill, as i never plan to produce four figure horsepower numbers and it is considerably heavy. Tremec boxes are extremely costly, rare to find in H pattern configuration and are generally available with very short ratios.
The AZ6 on the other hand, is widely available from a scrapyard in good nick, as there are no less than four cars to pull it from. Each car also has unique gear ratios which range from short to relatively long.
Note: changing gearbox has no effect on final drive. The final drive gear set is contained in the differential and must be substituted separately. I will be throwing different final drives (fd?) into the simulation to see which combination of gearbox / final drive is most effective, both with the new and stock transmission.


And now that you've read all that, on to Part 1.1! lol