Grand Prix Challenge is a clone of the arcade game Super Sprint II by Atari. In it, you can have several players at once, who are competing in the same race, to do several laps of each track. If one collects enough wrenches while racing, one can buy additional capabilities for their car at the end of each race (including extra traction, speed, acceleration, etc.). There are 25 tracks in all.
A personal theory of mine: The joystick controls are a little odd, in that moving the joystick left or right caused you to rotate left or right, as opposed to you just pointing in the direction you want to go. Now, Dave eventually released two games that used the Sega Master system's phaser gun (Iron Forest and Medieval Madness), and he was working on other things before he abruptly left the Coco world. I suspect that he may have designed the joystick controls for this game to eventually be used with a steering wheel/accelerator system, as the controls would be much more "natural" using such a system. Of course, this is complete guesswork on my part... although, I did, at one time, see a prototype for a Wild West style game for the gun system...
Title: Grand Prix Challenge
Author: Dave Dies
Publisher: Diecom Products
Released: 1987
Requires: Color Computer 3, 128K RAM tape or disk, joystick.