Quote:
Originally Posted by bradleyland
You can see the data I used to calculate these measurements here: |
I'm not sure I buy a weight per size measurement (density) as an indication of porkosity. The above chart is more a function of the molar weight of the chassis/car substrate than it is a measure of performance-per-weight, which is what the weight of the car is really affecting. Because the frame could be 300000000000000 square feet of some futuristic feather-weight metal and severely skew it; likewise it could be 30 square feet of cast iron and sway it.
Density = M/V, so you can make things more or less dense simply by changing the volume. So I could take your chart above and say, "Okay, let's increase the wheelbase by 50%," effectively decreasing the density by 50%. Does that mean the car is any less "porky?" not by any relevant standard, it's meaningless data-shifting. It performs the same in a straight line. Likewise I can say "Let's take the 3-series and decrease the wheelbase by 16%," which makes it more dense. But again, has any real performance metric changed? No.
The 2-series is a smaller car with the same things (weight) as a larger variant, so of course it is more dense. But density is fairly esoteric with regard to a vehicle because, as above, it has no real performance data implication. It doesn't necessarily mean anything has been "added" to the vehicle.
The variable that DOES relate to adding to the vehicle is the vehicle weight (mass). If the car is heavier, it performs more poorly regardless of its density. In that way, the equation becomes a function of weight instead of density, and there's already a tried-and-true method of interrelating performance based on weight:
Pounds/hp. How much weight does each hp have to pull?
A semi has a gigantic volume and thus a very low density (lb/sq. ft); would you contend that a semi is more weight-optimal and performs better than a smaller, less massive sports car?
Probably not.