Other way around. A ricer's turbocharged Honda might have 180hp and make it to 130mph, but it will take them forever to get there. Put that ricer up against a carbureted 350 chevy that also makes 180hp, it will win every race, even though the top speed is the same.Originally posted by Mercury140-I6:<br />I was always told that horsepower got you there (At any speed), but it was torque that kept you there (At that speed).<br /><br />Is that correct?<br /><br />Craig
No, it's you that have it backwards.<br /><br />It's a myth about torque gets you going, HP keeps you there AND visa versa. A car engine has no idea what speed it is going or how fast it is accelerating. It only knows the resistance placed on it. That comes from one of two things: inertia and friction(rolling and air resistance as well as from internal components). <br />Accelerating a car/boat from 0 - 60 for example may require the same amount of force to overcome inertia as the force required to overcome friction while maintaining 120. The difference is the force being produced from zero to sixy is more than the car requires hence it accelerates. At 120, the force required to keep it at that speed is the same. 'Course, these numbers are just as an example.<br /><br />The differerence, and hence all the confusion and complete miscomprehension is that there are two major variables when we're talking about automobiles and just about every application for an engine: The engine rpm changes (in response to an unblanced force, and as it does, the torque produced does, because of inhernet design as well as physics and chemistry). The other factor is that there is a transmission, even in an OB. The only place where we're concerned about the torque is at the place where it is put to use - prop or wheels. The torque of the engine is altered becasue of gearing. This obviously is especially true in say a 5 speed transmission. No one has to convince you that in 1st gear, you accelerate at say 3000 rpm much faster than in 5th gear at the same rom. The engine is producing the SAME amount of torque/hp in both cases. BUT, the torque at the wheels is much greater, even though the hp is the same. This is not to say that if you put an infinite amount of gears in a transmission that you will get a proportionaly increase in acceleartion. We are limited to engine redline for one. So, in first gear of say 100 gears, you would move an inch before having to shift. But even if an engine had in infinate redline and a perfectly flat torque curve (resulting in a linear rise in hp), you still can only accelrate the car so fast. This is a function of the torque produced, since torque is THE measure we use to define how powerful an engine is. Be sure to realize the distinction. We could pull a 100 car freight train using a spring found in a swiss watch IF we geared it right. You might have to wind the watch a billion times and the train may only move an inch over the course of a year, but the torque produced at the final drive gear would be the same as that of a 200 ton locamotive. So why does the locamotive do it so much faster? Horsepower. It produces the same amount of torque (at the final drive gear) but it can do it a million times faster. The reason for this is becasue the torque coming directly off the engine is so much more to begin with. Thus it can spin a gear faster and hence you arrive at its horsepower (torque x rpm). Becasue there is a standard defining one horsepower, it is hp that is conventionally used to calcualte acceleration, once all other variables are factored in.<br /><br />It is true the horsepower IS a function of torque. In somewhat simple terms, it is the twisting force any engine produces with time factored in - in this case, engine rpms. To get purely technical, hp is a measure of energy expended, not produced. Even a lightbulb can be measured in horsepower for this reason.<br /><br />Want proof? Compare a diesel engine to a regular gas engine. They often have twice the amount of torque for the horsepower produced as a gas engine - a result of a 20 to 1 copmpression ratio versus half that in a gas engine. This translates into much higher efficiency. Again, force produced with less energy expended (hp). Why are they [diesels] terrible to race with? This torque is produced at low rpms, so at hi rpms torque is comparatively low and thus so is horsepower.<br /><br />General statements like who would win a race are almost impossible to pass off as a general rule off thumb simply becasue the are too many factors to consider. Displacement, cylinders, 2 or 4 stroke, carburetion are the most obvious reasons.<br /><br />It really is a difficult concept to grasp. If you really want an accurate description, you have to consult an accredited textbook and forget about the plethora of 'opinions' that you find on the internet. Although, I have seen a few websites that do a good job of explaining all this, most do not as they are based upon word-of-mouth and all out assumptions.Other way around. A ricer's turbocharged Honda might have 180hp and make it to 130mph, but it will take them forever to get there. Put that ricer up against a carbureted 350 chevy that also makes 180hp, it will win every race, even though the top speed is the same.