Re: Re: Re: Re: All HP still not created equal....???

Posted by Joe on January 06, 2003 at 12:27:50 from (216.148.246.120):

In Reply to: Re: Re: Re: All HP still not created equal....??? posted by Steve - IN on January 06, 2003 at 10:39:24:

Its not that confusing at all. HP is a value that is derived from the torque and the rpm of the motor. When a internal combustion engine is given a HP rating that is usually at wide open throttle and at a specific rpm. That is 1 point in the entire operating rage of that engine. To really know what it can do, you should look at at the HP/torque curve for the engine which is probably hard to find in most cases. Here is an example for you. A modified Honda civic with a 4 cyl engine in a magazine makes 350 HP. A 454 chevy engine in a 4x4 truck is likewise rated at 350 horsepower. A modern John Deere tractor (I dont know displacement offhand) is rated at 250HP. Do you think for one minute that the two car engines are capable of what the tractor engine is? No. The reason isnt the HP, it is torque. That honda is revved to nearly 9000 rpm and wont hold all day to make its max power, while the 454 would probably be in the 4000 rpm range making 350 hp and would be able to sustain it for quite some time as there are many boats on rivers and lakes with this engine that operate in that range. And then the tractor. Its only 250 horsepower but yet could move many times what the car or truck could not only because of its weight and traction but because the torque that the motor makes. Line them up on a race track and who will be the quickest. Probably the Honda cause it only weights around 2000lb. It makes much more torque but only revs to a few thousand rpm so its horsepower rating is low. Remember HP is torque*rpm/5252. The faster you spin it, the bigger the HP number. If you really want to compare powerplants, you need to look at the torque, not just the peak, but the whole rpm range. As far as AC electric motors go, they seem to have more power. No they just make their full power at one constant rpm. they have high starting torque to get up to speed and thats it. The combustion engine has very little torque at low rpm.

Follow Ups:

• Re: Re: Re: Re: Re: All HP still not created equal....??? Steve - IN 14:27:37 01/06/03 (1)
  • Re: Re: Re: Re: Re: Re: All HP still not created equal....??? Joe 12:14:48 01/07/03 (0)

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