Calculating optimal individual gear ratios for a given tq/power curve is relatively straightforward. But how do you match a final drive drive for an engine? Or does it not work that way, in that you don't match a final drive to an engine, but only to a particular track (circuit)?

 

You're correct. FD is not matched to the engine solely, but what you are doing with that engine and the necessary speed required. It gets calculated both with the gear ratios being used and what needs to be attained at the particular track.

 

We like to think of the FD as a "fine tuning tool", used in conjunction with the overall gear ratios to increase/decrease the overall speed required for that particular circumstance.

Two tools for you to use:

1) Gear Calculator - http://www.teammfactory.com/gearcalculator.php
2) Torque Calculator - http://www.teammfactory.com/torquecalculator.php

Enjoy

 

By track.

Tired of chaning the FD in my close geared trans, I'll be building another two trannys later this year so I have three to choose from for any given track.

 

Most of the road racing track that I race at we hit a top speed of about 130mph max, thus I use the FD that will top out at about 135ish. Anything that gives a higher top speed is just going to give up acceleration, and anything lower will run out of gears.

Some of the big race teams change FD's and even gears based on track. That's not something I'm willing to do.