Model Bloat Vs Power 1975 - Present

"Sweet Trav" (thespunbearing) 12/18/2015 at 09:56 • Filed to: None

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Very interesting report from the EPA. For everyone who complains about model bloat, look at the trend of horsepower vs weight.

Full report here.

http://www3.epa.gov/otaq/fetrends.…

spanfucker retire bitch > Sweet Trav 12/18/2015 at 09:59

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Because having your cake and eating it too is just awesome.

sm70- why not Duesenberg? > Sweet Trav 12/18/2015 at 09:59

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“But just think how much faster it would be without air bags and crumple zones!”

/s

RamblinRover Luxury-Yacht > Sweet Trav 12/18/2015 at 10:08

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Counterpoint: I like the driving dynamics of a light car, and power covers a multitude of sins but not all. Back when I was driving a Rabbit Pickup I could barely give two shits it had no power - what made it compelling was, I don’t know, not being a lardass. I’ll complain about model bloat exactly as much as I like.

DrScientist > Sweet Trav 12/18/2015 at 10:09

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power is clearly increasing at a faster rate than weight. however, this may be misleading.

i have a feeling horsepower necessary to achieve equal acceleration is an exponential function of weight.

we need to see those curves at least matched when the weight curve is raised to that exponent. not sure if this is a squared or cubic exponent, physics is not my branch of sciencing.

others should chime in.

PS: poor 1980. :(

youshiftem > Sweet Trav 12/18/2015 at 10:52

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Looks like a 1987 model is the year to have. Just another reason to buy a Grand National.

DrJohannVegas > sm70- why not Duesenberg? 12/18/2015 at 10:53

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Live fast, die young.

/seriousbusiness

RamblinRover Luxury-Yacht > DrScientist 12/18/2015 at 11:01

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In theory, rate of acceleration is directly related to the torque the drivetrain gets to the wheels. F=ma, yo. That should be the torque at the engine times some quantity unrelated to how heavy the car is. In practice, it’s really not that simple. Rotating masses required to lay down that force themselves have to undergo angular acceleration, and rotational inertia increases as the square of the radius of the rotating mass. The ability to handle torque is (roughly speaking) also related to the square of the radius. So, for every 10% increase in power the system can handle, there’s an extra 10% inertial resistance to “instant-on” power, even before the weight of the vehicle comes in. So in a sense, drivetrain weight gets counted twice, in two separate ways, and while shafts/etc. don’t count for all that much, it’s MASSIVE for wheels, tires, brakes, which also have to be bigger to withstand weight of the car the larger you get. Also, shocks to the system increase in their effects relative to the comparison of the two squared radii, so a minor “pop” at the wheel if it’s big does horrible, horrible things to shafts. Which increases how big they have to be to be safe. And rotational inertia.

Also, Newtonian friction says that the tires can apply force to push the vehicle forward proportionally to the normal force (i.e. weight of the vehicle), but there’s a point of diminishing returns in reality. A tire with 3000lb applied to it can’t usually *really* apply double the tractive force of that tire at 1500lb. So, you can’t design the driveline to be able to lay down power in quite the same way, or you Smoke Tires Erryday. And as we all know, kinetic friction is less than static friction.

tl:dr: yes, the weight of the car increases driveline weight, which then gets counted twice in a sense, so between two cars with the same p/w, the lighter car likely has an advantage.

PS9 > DrScientist 12/18/2015 at 11:26

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It would be misleading if cars were not getting any faster because of the weight. But considering the increase in power from 1980 to 2015, that would be a serious charge to make. To use Americas most popular car as an example;

In 1983, A Toyota Camry weighed 2,315 lb and made 92HP in base trim. (24 lb/HP)

In 2015, A Toyota Camry weighs 3,240 lb and makes 178HP in base trim (18 lb/HP)

Even with almost 1k lbs additional weight, we can see here that an 2015 Camry would easily vaporize it’s 1983 ancestor. A 4 lb/HP reduction doesn’t sound like a lot, but imagine this same match up between two cars both having 92HP, only with one of them being 1.5k lbs lighter than the other. The lighter car in this case

A world where cars aren’t getting any faster despite the power increases would also be a world where the power/weight ratio between generations would be constant. a 24lb/HP camry in 2015 is a 4,200 lb Camry; it would weigh as much as a Tacoma.

Blunion05 drives a pink S2000 (USER WAS BANNED FOR THIS POST) > Sweet Trav 12/18/2015 at 11:48

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This is readily obvious without a report from the EPA.

My personal problem with model bloat is that increased weight leads to lowered cornering performance. Equipping tires with more grip will help a little, but not much.

I’m surprised the EPA didn’t throw in showing how average tire grip levels have increased since 1975.

I recall watching a Best Motoring episode where it showed an S2000 on soft compound street tires having the same level of grip of a racing spec R32 GTR on racing slicks 10 years prior.

HammerheadFistpunch > Sweet Trav 12/18/2015 at 11:57

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I remember getting so much crap for suggesting that cars today (on average) are heavier than they used to be. (nuh uh! old cars are heavy!). oh rly?

DrJohannVegas > HammerheadFistpunch 12/18/2015 at 12:18

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I think it all turns on your definition of “used to be”.

HammerheadFistpunch > DrJohannVegas 12/18/2015 at 12:25

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I would love to see the data curve before 1975, I think it probably went up then down. The truth is that even as big as the old luxo-barges were...new cars are HEAVY. A 70’s deveille convertable is within a 200-300 lbs of a cts-v for example.

RamblinRover Luxury-Yacht > PS9 12/18/2015 at 14:26

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As I covered in my response, p/w is helpful to determine quickness, but has its limitations, and to some extent a heavier car has to do better than break even to actually be as quick. Driveline losses, wheel design, and other points are nonlinear.

Even without considering those limitations, there’s a lot to be said for the part played in *feeling* quick by lightness. Robustness to handle the more driveline power needed is often via smoother delivery of said power (which hurts feeling quick), the car itself is better insulated from the outdoors by its deadening bulk (doesn’t sound as quick), sits more firmly on the road relative to the scale of effect from road disturbance (doesn’t feel as quick), has a much greater fore and aft rotational inertia and better damping (doesn’t tilt/lurch much, which doesn’t seem quick), etc. etc. etc. To seem as quick to the driver, a heavy car has to do way better than have the same power to weight.

No, that 3240lb Camry feels safe , which is bullshit.

PS9 > RamblinRover Luxury-Yacht 12/18/2015 at 18:37

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Are you suggesting we prioritize driver ‘feel’ over empirically observed data? Because...no. ‘Which car is the fastest?’ is a question you can only answer with numbers and observations. ‘Which car feels better to drive?’ is a different question, the answer to which cannot overrule empirically observed results. Peoples thoughts and feelings don’t have precedence over reality.

It doesn’t matter that your BRZ ‘feels’ faster around the track than your friend’s V6 Mustang. If the observations say it isn’t, then it isn’t. ‘But I like how the BRZ feels to drive more than the Mustang’ is a subjective judgement anyone is well within their right to render. But that by itself will not be a counter to empirical observations.

RamblinRover Luxury-Yacht > PS9 12/21/2015 at 09:49

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Setting aside that you chose to ignore my first point (that p/w ratios aren’t completely transparent and have second and third order effects with increase in weight), you’ve set up a misstatement to attempt to make me look foolish (that the car which feels faster should be considered faster) and you’ve set up a false dilemma between feeling fast and being fast on paper. Mostly, though, you missed the central point of what I was stating in the second part, and based your whole comment on that miss. Ready? Here goes: what affects the “feel” of a thing is mostly quantifiable. The whole point of listing things which have an effect on how something feels is that regardless of variation in the consumer, certain things have observable effects in scope and are really easy to predict. We say plenty of cars have hard suspensions, a smooth ride, good power delivery, well-managed NVH without a single one of those things being anything more than a value judgment, but most “feel” value judgments are based on something that has a number, or several somethings. Altering feel is in no way chasing a will-o’-the-wisp, just a study in compromises. Weight and its friends usually win.

Did I say that automakers should typically prioritize feel over performance? No (well, maybe once they’ve reached diminishing returns). But in some cases, they might prioritize feel (quantifiable, mind you!) over making the car feel like a bank vault for other reasons (another kind of feel, also quantifiable).”Feels better” is nebulous, “feels faster”, less so. A sports car is not supposed to come across as a smoothed-over aircraft carrier, even if it has good performance numbers. The reason for my seemingly nonsensical crack about the Camry is that the drive toward heavier cars, while prefaced largely by safety, also keeps up with other reasons for a heavier car (quietness and gimmickry) to the detriment of driver experience and the companies know that they’re doing it. Because the median customer of the median car wants the compromise, and I don’t, really. I was stating a preference: if I have a sports car, I want it to feel like one, not a grocery-getter that just surprises me when I look at the speedo. Back to the false dilemma, it’s possible for a heavy car to have all the “feels” of being fast in order. The Viper is the most extreme example that comes to mind. It pitches hard, revs hard, sounds loud, bounces around, and in general has very little capital invested in feeling safe. I don’t want a Viper, really, and there’s the only flaw: prediction of scale, the study in compromises again.

Let’s also review *why* most people want a car that puts out good performance numbers, which, as you observed, are straightforward and easy to calculate. These people want either bragging rights, or to be assured that they have a fast car, which in their mind equates to the joy they will get from driving. If, by the application of more power, harder sidewalls, and piles and piles of trickery, the car turns out good numbers in a dull way, I would argue that customer #2 has been cheated. For the average driver, the *exact* 0-60 time and time around a given track mean little to nothing for his everyday driving. You’ve meant to point out what’s quantifiable, but at the end of the day, that’s just one more quantifiable number that affects the driver’s perception of driving. Like peak G-force under acceleration, pitch angle at maximum acceleration and braking, rebound over a given obstacle...

JR1 > RamblinRover Luxury-Yacht 02/05/2016 at 21:26

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If you enjoy the sheer fulfillment of lightness what the hell are you doing with a 5000 pound aircraft carrier?

RamblinRover Luxury-Yacht > JR1 02/06/2016 at 14:12

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Large percentage increases are most typically seen in allegedly small cars, so model bloat of small cars is a big (ha ha) thing. Cars that are big and stupidly heavy to start with aren’t experiencing that kind of bloat, so it’s disproportionately small to midsize cars getting ruined for what they are. Also, it has a lot to do with size appropriateness of bulk. There’s something wrong with having the interior space tradeoffs of a small car and still having it go KLONK over every bump because the suspension is so hard to compensate for the fact it’s so heavy for its size that its “natural” dynamics are insane. The CVN-72 (Abraham) Lincoln has a low C.G. for its width and length, so roll and pitch don’t have to be fought as *violently*. Stability, yo. There’s also something wrong with the smallest cars you can buy increasing in weight year over year. Anyway, driving a small light car, that’s what the Ranchero is for. I can totally have different cars for different wants.