Quote:
Originally Posted by drakensoul
Aww, I thought it was pretty simple  At this point it's becoming esoteric and 
I thought the point was that density is a poor metric of vehicle performance. That is what you're comparing, no? Otherwise you would have just listed older BMWs compared to newer ones to show that BMWs have become relatively more dense. If you're comparing it to other cars you are implying that it somehow relates to performance, otherwise you're saying something is more dense just to say it's denser with no real purpose. What's the point? I was assuming you weren't making an argument just to beg the question.
I was highlighting that footprint density is a (very) poor comparator of performance by virtue of being almost entirely based on the exponential variable in the denominator (vehicle length and width).
I.e.: you can equilibrate the footprint density of the 235 with the SS by shaving 160 pounds off of the 235, but it's still massively outmatched with its current engine (still 670 pounds overweight to equal performance of the SS based on ~8.2lb/hp for the SS). In other words, the 235 would need to weigh <2700 pounds with its current engine to match the SS's performance, even though it's only 160ish lbs off in density. Quite a gap there, no? Because density doesn't relate well to performance.
Heft/weight per HP is a meaningful comparison variable for performance because it actually is a metric of performance (ability to overcome inertia), and density again plays almost zero role because density is based exponentially on footprint or volume.
But if you were saying that it's denser just to say it's denser... using a formula that has near-zero bearing on performance, then... okay? 
Edit: And I don't own or want to own a Camaro! I'm still deciding between used 235 or leasing a new 240.  |
It's only becoming esoteric because everyone keeps walking right past the point in to some digression about density. Alas, that's the discussion you'd like to have so let's jump right in that pool: Density is bad because it makes cars heavier. Heavy cars are bad when it comes to handling and performance, but more so handling. In order to preserve performance (0-60, 1/4 mile, skid pad, slalom, lap times, etc) you can mitigate weight gain by adding more power, larger tires, brakes, etc. However, it is much more difficult to preserve handling (the way a car feels) as you add weight.
My E92 M3 is the biggest, heaviest car I've ever owned. I love the engine, and I think the car drives well for its size, but it's still too big and too heavy for my taste. When not driven beyond the limits of its suspension, my MkV handled better than my M3. Once you pushed the GTI past 7/10ths, it's poor damping ruined the fun. That car weighed around 2,900 lbs.
If all you care about is chasing numbers, then you're right, density means nothing. Simply dig up all the performance figures you can find, and buy the car that hits the performance targets you're looking for. If you care about handling, then the constant march toward heavier and heavier cars must matter to you. Ultimately, it's the curb weight number that really matters: lower is better. Compared to many of the cars on that list, the M235i/M240i is the lighter car. That's a good thing, but the M235i/M240i are not as light as they could be, and that's a bad thing.