HP vs TORQUE? What's better??

Pushrod said:

what's tractive effort?

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Oh man, this post is making John sway back and forth in his chair.

Here is the short & simple answer. Your engine produces torque. It produces a different amount of torque at each and every RPM.

Horsepower is the "work" done by the motor. It is derived from torque. From math class, "horsepower is a function of torque". A dyno measured torque, and uses those measurements to calculate horsepower.

When someone says their car puts out 285 ft/lbs of PEAK torque, and 215 PEAK HP, what you can INFER is that the car has a lot of LOW-MID range power, but the High range power is minimal. This is the case for the stock 5.0L. You need to shift very early (5000 rpm's). The torque shoots up at 2000 rpm's, and stays high until 3800 rpm's. After 3800, it falls VERY FAST.

So that means that at "lower" RPM's, you have a lot of power, but at "higher" RPM's, your power falls off. This is the conception that our cars are "torquey", or have great "low-end" power. The low-end refers to the fact that in the lower rpm range, you have lots of power.

So, then you look at a LS1, which has over ~320tq (guess, not correct), and ~320 hp. From this, You might think that the car has an even amount of power throughout the powerband. It's peak HP is close to it's peak torque. This probably means the torque curve is very flat, and stays that way until after 6000 rpm's. It's true. They have great low, mid, and high end power.

What makes the LS1 a much faster car than ours, it's the fact that they have high end power. Because they can stay in each gear until 6000+ rpm's, they can take advantage of each gear much more than we can.

Now, you take the 1999/2001 Cobra's. They put down about the same peak numbers as the LS1, but here is the catch. They have much greater high end power. They can take their motors all the way to 7000 rpm's. This means they can take an even greater advantage of gearing.

Thus, the 1999/2001 cobra's have a better "drag strip" motors. When you drag, you only see the lower section of your RPM's for a brief moment (1st gear for the launch). After that, it's all in the upper rpm's. Low/mid range torque will not help you at the track (realistically). It's all about the high range power.

Just to cover it, Horsepower is a very misused term, and can make things very confusing. Secondly, using peak numbers to describe a motors performance is absolutely rediculous. The real way to determine a motors power is to look at the torque numbers for the entire RPM range. Then, you can determine if the car has a low, mid, or high range of power.

If you know what you are looking at, you can use horsepower to get a good idea of the car's potential. But you really need to realize what the HP curve is telling you. If you just go straight to the peak HP point, and say the car has XXX HP, you will be extremely wrong.

The perfect, or ideal motor, would be one that produces the same amount of torque, for the entire RPM range. It's impossible, but a few motors get close. The 2003/2004 cobra motor is very close. The car puts out 400 ft-lbs of torque at 2000 rpm's, and it stays there until redline. This then defines the motor as having EQUAL low/mid/high range power.

For a more detailed explaination, go here.
Scott