My opinion on 談談功率和扭矩(小結)：馬力是金

http://web.wenxuecity.com/BBSView.php?SubID=auto_best&MsgID=5322

The original article above concluded that
最大驅動力取決於引擎的馬力,和引擎的最大扭矩無關

This statement is theoritically true. I believe this is kind of misleading.
扭矩(torque) is still a very important factor to the performance of the car.

For example, we can put two engines below on the same car.
We will use a formula: hp = (torque * RPM) / 5250

engine#1 has flat torque
200 (lb-ft) from 1000rpm to 5000rpm
peak power is 200*5000/5250=190hp

engine#2 has a ^ shape torque,
100(lb-ft) at 1000rpm
linearly increase to 400(lb-ft) at 3000rpm
linearly decrease to 100(lb-ft) at 5000rpm
peak power is 400*3000/5250=228hp


Let make a test run and compare these two engine performance side by side
Let's assume that the vehicle has the such gear ratio at first gear
when vehicle runs at 10mph, the engine runs at 1000rpm
when vehicle runs at 30mph, the engine runs at 3000rpm
when vehicle runs at 50mph, the engine runs at 5000rpm

When the car starts, it is on first gear,
As you can see, at 10mph, engine#1 gives bigger drive force (驅動力) than engine#2 at the beginning
although engine#2 has bigger peak power.

So, Engine#1 (flat torque with less peak power) performs better
than Engine#2 (^ shape torque with more peak power).


Of course, you can say that at 10mph, engine#1 provides more horsepower (38HP)
than engine #2 (19HP).

But when you buy cars, you were only provided information of the PEAK horsepower.
If the car has unlimited number of gears so that you can always ajust the engine
run at the peak power at any speed, then you need only care about peak horsepower.

But the reality is, each car only has limited number of gear ratio. Therefore,
many times, especially at lower speed, you have to make engine run at non-peak
horsepower mode. At this time, the flat torque engine performs better because it
provides better horsepower and drive force earlier than ^ shape engine.

Overal, this statement is right
最大驅動力取決於引擎的馬力,和引擎的最大扭矩無關

But don't fool yourself by just looking at peak horsepower. The more scientific way is to look at the power curve shape (not the torque curve) against rpm.Usually the flat torque engine will boost power faster at low
rpm than ^ shape engine

所有跟帖： 

• you r right,low RPM&high torque engine is better than the engine -fixanycars- ♀ (0 bytes) () 07/01/2009 postreply 11:33:18

• More scientific graph for engine -wolfmanii- ♂ (468 bytes) () 07/01/2009 postreply 11:49:15

• 我已經從理論到實例說得很清楚了 -TBz- ♂ (72 bytes) () 07/01/2009 postreply 13:32:47

• i think he knows that too. read his posts carefully -潤濤閻- ♂ (48 bytes) () 07/01/2009 postreply 12:26:19

• 謝謝 -TBz- ♂ (10 bytes) () 07/01/2009 postreply 13:47:05

• 回複：謝謝 -wolfmanii- ♂ (625 bytes) () 07/01/2009 postreply 13:59:53

• 也謝謝您的賞光 -TBz- ♂ (85 bytes) () 07/01/2009 postreply 14:14:57

• 回複：也謝謝您的賞光 -wolfmanii- ♂ (231 bytes) () 07/01/2009 postreply 18:36:30

• How about this: Torque means Power for a given RPM -wolfmanii- ♂ (1302 bytes) () 07/01/2009 postreply 19:02:01

• 你這個比喻是對的。 -潤濤閻- ♂ (0 bytes) () 07/01/2009 postreply 20:42:24

• Don't forget the function of transmission -TBz- ♂ (165 bytes) () 07/01/2009 postreply 22:04:52

• 回複：Don't forget the function of transmission -wolfmanii- ♂ (1181 bytes) () 07/02/2009 postreply 06:34:16

• 還可以更仔細地說。力矩還是牛。 -UberAlles- ♂ (444 bytes) () 07/02/2009 postreply 06:30:27

• 力矩 馬力 一家人 -wolfmanii- ♂ (535 bytes) () 07/02/2009 postreply 07:03:18

• 力矩 馬力 一家人, 一樣牛 -wolfmanii- ♂ (1210 bytes) () 07/02/2009 postreply 08:57:29

• 回複：力矩 馬力 一家人, 一樣牛 -UberAlles- ♂ (539 bytes) () 07/02/2009 postreply 11:57:00

• 回複：回複：力矩 馬力 一家人, 一樣牛 -wolfmanii- ♂ (48 bytes) () 07/02/2009 postreply 12:04:56

• 多數情況是最大扭力到最大馬力那段轉數跨度越大越好， -extrayida- ♂ (128 bytes) () 07/01/2009 postreply 12:43:44