
Originally Posted by
Double L
It's not the horsepower that gets the trucks moving, it's the torque. Horsepower is just simply to maintain speed. The reason why the higher horsepower engines seem to be more powerful isn't cause of the horsepower but the increase of torque. Example:
475 horses produces about 1875 ft/lb of torque at 600 horses produces about 2200 ft/lb of torque.
I don't remember if those are the exact numbers but it's just an example anyway.
BUT that is just half the equation though. There are so many different rear end gearings and transmission set ups. You can take two identical trucks with the same horsepower rating and torque rating but have a different tranny and rear end and one truck may run it's rear off but the other truck will struggle.
This post is representative of a very, very common misconception.
It's not torque that moves a truck, it's horsepower. NOT peak horsepower, but horsepower none the less!
Torque is a number you measure. Horsepower is a CALCULATED figure derived from the TORQUE measured at the flywheel, or at the wheels most of the time.
ANY time you have torque moving at ANY RPM, you have horsepower.
HP = (torque x RPM)/5252. Period.
You could have all the torque in the world, but if there is NO rotation, or movement, you have 0 horsepower, and 0 movement. I could stand on a pipe on the end of a wrench, and have just as much torque as one of our heavy diesels puts out. Does that mean I have the power to get a truck moving? Not quite.
Say your truck produces 100 lb-ft of torque at a 600 rpm idle. Our formula for HP would mean that you are putting out 114 HP. THIS is what is getting your truck moving. That motor at idle is pulling JUST AS HARD as a little 1.8L honda civic motor is, when it's at peak horsepower. Yes, that's right, if you could gear a honda civic motor to put out it's peak horsepower, somewhere around 6,000 rpms, at a road speed of 1-2 MPH, that little motor would launch your truck just as fast. All this at 100 lb-ft of torque...but a MUCH HIGHER RPM.
So, if you have a motor, want to give it more HP, all you have to do is increase the RPMs where the PEAK TORQUE is, to make that same amount of torque work harder, because it's spinning faster. If you take a detroit diesel series 60, push it's 1650 lb-ft of torque to 2,000 rpm, you would have 628 HP, with that "little" 1650 lb-ft of torque!
end of rant....flame away!!!
