Don49

iTrader: (3)

The Case For Torque
Now, what does all this mean in carland?

First of all, from a driver's perspective, torque, to use the vernacular, RULES :-). Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve (allowing for increased air and rolling resistance as speeds climb). Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same.
Here's the link to the site where I got this: http://www.4x4abc.com/jeep101/torque.html

In a nutshell, a higher torque peak will accelarate you faster by allowing you to rev higher and take advantage of the gearing.

peejay

Wow, that is still floating around? I was there when Bruce (Dickenson?) first posted that to Usenet around 1993-ish.

It is obvious that, while you may have read it, you didn't actually learn anything from it. Read it again; it states my case. Shifting for highest average HP is shifting for highest average acceleration.

Peak torque is peak acceleration in a given gear, but peak HP is peak acceleration at a given speed. That whole gearing thing. Read that article again... or did the Jeep club cut out major chunks of it?

Don49

iTrader: (3)

Peejay,
Not looking to start an argument, but I think we are saying the same thing but expressing it differently. Since HP= tq xr pm divided by 5252 there is a pure mathematical relationship between the two and the average torque in your example would mirror the hp.

j9fd3s

iTrader: (3)

does he put his pants on one leg at a time?

there is also this one http://www.yawpower.com/tqvshp.html

peejay

Torque is just force, you can have torque without any motion at all. Horsepower is work, it's force exerted over a distance (rotational distance in this case) over a period of time. Acceleration is work. We want the highest average horsepower for acceleration. This will work out to be the highest average torque *at the wheels*, but not at the engine, because of that pesky gearbox in the way.

Peak torque is fine and dandy, but if you ever see peak torque when accelerating through the gears, your powerband is too peaky or your transmission is not closely geared enough.

TheAbsence

iTrader: (19)

I retract part of this statement. I understand what peejay meant, but hes assuming that the powerband is symmetrical near the peak.