jeff@qubix.UUCP (Jeff Buchanan) (06/21/84)
> The torque ratings shown in your owners manuel are in a no load situation. > This indicates when your engine can develop the most torque for a > given load, but does not account for the interaction of load and torque. > Thus the Porsche study does not "violate" the laws studied in Thermo. > Naturally the empirical Porsche study must be correct. The first statement is obviously not true, I'm sure the author didn't mean it in that way. It would be meaningless to give a torque figure at no load/ minimum throttle setting (idle). If an engine is operating at no load and is at constant RPM (regardless of what RPM) then it is producing zero torque. Actually, zero net torque. The torque produced would be entirely used up in overcoming all losses interal to the engine (bearings, ring friction, windage, etc.). The torque figures in owners manuals are at maximun throttle. Example: a 430 HP 427 Chevy is rated at 450 ft.-lbs. @ 5200 RPM. This assumes wide open throttle, engine developing max HP and torque at that particular RPM. The load is simply the external force needed to exactly equal the net torque produced, in this case, 450 ft.-lbs. As far as "the interaction of load and torque" this implies one is a function of the other. Not true; torque is a rotational force produced by the engine. The load is an externally applied force (in the opposite direction of the torque), like the brake on the dyno or wind resistance. The inter- action is of load and RPM. IN other words, the RPM varies with load, and also varies with torque, but changing the load does not directly affect torque. It affects torque only because the RPM is affected and RPM does affect torque. I would agree that the empirical study would probably be correct. -- Jeff Buchanan @ QUBIX Graphic Systems, Inc., Saratoga, CA. ...{decvax,ucbvax,ihnp4}!decwrl! ...{ittvax,amd70}!qubix!jeff decwrl!qubix!jeff@Berkeley.ARPA