I just came up with it. It's meant for friendly games. I saw this as a means of doing chariot racing, but for 40k.

Racing in the 41st millennium (These are changes to the normal stats)

Models that have an armor value have: Models that have a save have:

AV of 10 = Strength 4 Normal Stats
AV of 11 = Strength 5
AV of 12 = Strength 6
AV of 13 = Strength 7
AV of 14 = Strength 8
One Attack

Models that cannot move more than 6? cannot participate. Turbo Boosting may only be used once per race, and the next time the model wishes to move, does so at –3?. Note that standard movement penalties to shooting still occur. (A model that has an armor value moves 12? can’t shoot with a main weapon.) There are no sweeping advances, and there are no leadership tests.

The armor value counts as the Toughness and the Save. Open-topped vehicles add +1 to any armor penetration roll or glancing roll. Tanks and vehicles can buy upgrades, using the following chart:

Models with an armor vale can buy up to 30 points of vehicle upgrades, models with a save can buy up to 30 points of any wargear, from the representative codex.

If a model moved more than 12? inches into another model, then the model gets +1 Attack. If the move was more than 18?, then the strength all attacks is +1.

When moving into a vehicle, the player must declare it and roll 1D6 for every 6? he moved this turn after moving 12?. In addition, the player must roll 1D6 for the 12? he moved to begin with. Roll a scatter die in addition to the number of dice. If the scatter rolls a hit, then add +1 to the strength of the attack.

If the total number of the roll of the dice is less then 10, the assault goes well. Move the model that is assaulting next to the target. Roll to wound, or roll the extra D6. Make armor saves, or roll and consult the damage charts. If the result is 10 or more, then the assault fails.

If the assault fails, move the number of inches shown on the dice and in the direction of the scatter die. If the model hits a wall and moved more than 16?, then remove the model. If the model rolled a number in between 10 and 16, the model moves in contact with the wall and takes a hit at strength 8. Roll one D6 in addition to that if the model has an Armor Value.

If a player wishes to shoot at a target, then you use the model’s BS and compare the range. A model that moved 12? last turn has no penalty against the firer, but if the model moved more than that, for each 6? increment after 12?, roll to hit at –1. A model that moved 24? last turn and is being shot at is hit at –2.

The turn is played out like this:
Roll for Initiative: Each player rolls a D6 to see who goes first. Reroll any ties.
Movement Phase: Move all models in the order of the initiative. Resolve any assaults.
Shooting Phase: Shoot with the available models that can shoot. Go in the order of initiative.

Hope this actually creates some positive feedback!