acceleration / power curve

jusdorange · 03-09-2014, 01:47 PM

something I've always wondered;

what part of the 0-60 does the car accelerate most ?
what makes two cars with the same 0-60 vary in say 40-60 mph?

I don't really know much about cars so torque etc confuses me

in that will a car with more torque be faster overall ? or does it depend in what part of the rev range it develops it?

thank you

sn3rd · 03-09-2014, 02:11 PM

You need to think in terms of the science.

Torque essentially describes the maximum force that can be applied (numbers quoted by manufacturers are usually at the fly, while you would mostly be interested in the numbers at the wheels). Power describes the amount of work that can be done per unit time. So torque describes an instant in time, while power describes a time interval (albeit a very small one).

By now you should be thinking "but force (i.e. torque) can do work," and you would be absolutely correct!

The numbers manaufacturers quote are the peak values at a given RPM; this is the maximum the motor is able to deliver, as well as the particular rev range at which it occurs. Unfortunately, peak numbers rarely tell the whole story, and so the curves you allude to are essential to understanding how a motor performs.

A motor that performs fantastically from 1000 RPM to 1100 RPM and then tails off dismally for the rest of the rev range is going to be a terrible drive; likely loads of wheel spin off the line followed by lackluster acceleration thereafter. Remember that you have diminishing returns, too; a 100 kW car will not accelerate twice as fast as a 50 KW car because physics does not allow this, and remember that the driver is central to all of this. So motors are typically designed to have steadily increasing power and torque curves so that a driver experiences what feels like smooth, constant acceleration, instead of having flat torque and power curves that would yield slower acceleration the faster you drive.

So the answer to your question is unfortunately "it depends". Ideally you want a motor capable of generating peak torque and power right away at low RPM, and to continue this performance linearly right until the redline due to exponentially increasing power and torque curves, but this is unrealistic.

Bonus: a guesstimate answer to your question is that you would probably feel the most acceleration mid-gear.

03-09-2014, 01:47 PM	#1
jusdorange YOLO 440 Rep 2,854 Posts Drives: #mw Join Date: Dec 2013 Location: Monaco iTrader: (0)	acceleration / power curve something I've always wondered; what part of the 0-60 does the car accelerate most ? what makes two cars with the same 0-60 vary in say 40-60 mph? I don't really know much about cars so torque etc confuses me in that will a car with more torque be faster overall ? or does it depend in what part of the rev range it develops it? thank you
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03-09-2014, 02:11 PM	#2
sn3rd Enlisted Member 2 Rep 46 Posts Drives: 2013 F30 335i Join Date: Jul 2013 Location: South Africa iTrader: (0)	You need to think in terms of the science. Torque essentially describes the maximum force that can be applied (numbers quoted by manufacturers are usually at the fly, while you would mostly be interested in the numbers at the wheels). Power describes the amount of work that can be done per unit time. So torque describes an instant in time, while power describes a time interval (albeit a very small one). By now you should be thinking "but force (i.e. torque) can do work," and you would be absolutely correct! The numbers manaufacturers quote are the peak values at a given RPM; this is the maximum the motor is able to deliver, as well as the particular rev range at which it occurs. Unfortunately, peak numbers rarely tell the whole story, and so the curves you allude to are essential to understanding how a motor performs. A motor that performs fantastically from 1000 RPM to 1100 RPM and then tails off dismally for the rest of the rev range is going to be a terrible drive; likely loads of wheel spin off the line followed by lackluster acceleration thereafter. Remember that you have diminishing returns, too; a 100 kW car will not accelerate twice as fast as a 50 KW car because physics does not allow this, and remember that the driver is central to all of this. So motors are typically designed to have steadily increasing power and torque curves so that a driver experiences what feels like smooth, constant acceleration, instead of having flat torque and power curves that would yield slower acceleration the faster you drive. So the answer to your question is unfortunately "it depends". Ideally you want a motor capable of generating peak torque and power right away at low RPM, and to continue this performance linearly right until the redline due to exponentially increasing power and torque curves, but this is unrealistic. Bonus: a guesstimate answer to your question is that you would probably feel the most acceleration mid-gear.
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