What 0-60 acceleration would you accept for good fuel economy?

[jamesqf]

Originally Posted by Clev

Fortunately all cars decelerate well enough to get out of that situation.

Not necessarily. He was even with the rear wheels of the tractor, so to get to a safe position had to either move 10-15 feet ahead, or maybe 4 times that to the rear. Could he have decelerated quickly enough? Maybe, but then he'd have been moving very slowly, and thus risking a possible rear-ender from following traffic.

[Clev]

Originally Posted by SuperTrooper

My point is: Do you think that a car that takes 20 seconds to reach 60 mph could have accelerated out of that situation?

I don't.

I guess my next car should go 0-60 in 4.5 seconds. After all, what if I was at the trailer's rear wheels? Do you think a car that takes 7 seconds to reach 60 mph could have accelerated out of that situation?

My point is: acceleration shouldn't be the only, or even default, option. The situations where acceleration is the only way out are extremely rare, and in most of those cases, it's the driver's fault for getting into them (i.e. pulling out in front of a fast-moving vehicle.)

[roflwaffle]

W/ the auto stop/start systems I've seen popping up as well as six speed manual boxes there is absolutely no reason to not be able to put out something compact that'll do 0-60 in ~6-8s and average ~50mpg. Acceleration and efficiency are not exclusive.

[Clev]

Originally Posted by roflwaffle

W/ the auto stop/start systems I've seen popping up as well as six speed manual boxes there is absolutely no reason to not be able to put out something compact that'll do 0-60 in ~6-8s and average ~50mpg. Acceleration and efficiency are not exclusive.

True, but that same car that does 0-60 in 10 seconds might get 55 mpg or more, and 6 seconds is faster than an '89 Ferrari Testarossa. Cars needing 6 second 0-60 for "safety" reasons is exactly the same logic that people use to justify commuting in an Excursion.

[SuperTrooper]

Originally Posted by roflwaffle

W/ the auto stop/start systems I've seen popping up as well as six speed manual boxes there is absolutely no reason to not be able to put out something compact that'll do 0-60 in ~6-8s and average ~50mpg. Acceleration and efficiency are not exclusive.

The 2009 Jetta TDI DSG does it in 8.0 seconds (MotorTrend) and will get 50+ mpg in the real world.

SHAZAM!

[BlackDeuceCoupe]

Originally Posted by SuperTrooper

SHAZAM!

Exactly!

I agree with you!

There's nothing wrong with having a 8-second cake, and eating it too...

[tasdrouille]

Had you been in a 20 second car, you would probably just have stayed behind the big rig. Since you were already at the tractor when he started to drift, he knew you were there and coming. He probably had judged your speed, the speed of the truck in front and was starting to pull left a bit so he would not have to swerve. But anyway, even if you had not been able to pull it, I don't see why the big rig would not have braked or pulled left earlier before you could pass him. It's not as if the truck in front just popped in his face out of nowhere.

[SuperTrooper]

Originally Posted by tasdrouille

Had you been in a 20 second car, you would probably just have stayed behind the big rig. Since you were already at the tractor when he started to drift, he knew you were there and coming. He probably had judged your speed, the speed of the truck in front and was starting to pull left a bit so he would not have to swerve. But anyway, even if you had not been able to pull it, I don't see why the big rig would not have braked or pulled left earlier before you could pass him. It's not as if the truck in front just popped in his face out of nowhere.

I'm pretty confident he had NO IDEA I was there. He put on his blinker and IMMEDIATELY started to pull into my lane. I barely got past his bumper. I bet I scared the crap out of him. He also started the lane change much earlier than I expected, since he still had about 400' to the lowboy. I think he was trying to change lanes before other cars further back trapped him behind the lowboy, and while focusing on them he didn't see me.

[jamesqf]

Something to think about: the fuel economy vs acceleration thing seems to be an artifact of internal combustion technology: that is, there's no physical law that says that the energy needed to reach speed X depends on the rate of acceleration. (Just the opposite, in fact.) So if you had an electric car, or a hybrid with good boost, it seems that you would no longer be affected by that tradeoff. Do 0-60 in 5 seconds, or 50, the energy used would be the same.

[dcb]

There exists a fundamental compromise between acceleration and economy regardless of the technology. There are practical limits (low and high) on efficient acceleration once you look more closely than f=ma.

More acceleration means:
1. more internal losses (battery losses, bearing loads, fluid drag)
2. more time spent at higher speeds, thus more aerodynamic losses.
3. more weight for more power to do the accelerating with.
4. increased braking losses over time (faster and heavier)
5. increased hysteresis in the flexible parts if the driveline