stuart@ssc-vax.UUCP (Stuart Lewis) (05/01/84)
In response to Jeff Buchanons' article on L-88's and ZL-1's (which I enjoyed greatly - thanks Jeff), he discussed dyno testing and h.p. ratings. Maybe I can throw a little more light on the subject. First of all, factory ratings on these big monsters were nearly always on the conservative side. Federal law, namely the Federal Trade Commision, requires that among other things, when the factory places ratings on torque, horsepower, et.al., that these must be the MINIMUM rating that EVERY motor of it's certain designation must be capable of producing. I.E., they may produce more horses, but not less than the factory rating. So every L-88, ZL-1, LS-6, etc., out the door must produce at least as much as the factory says it will. You can begin to see where the factory must have some kind of "buffer" horsepower held in re- serve for all their engines. (Another example is ratings on stereo equipment - i.e. every receiver must produce at or below its total harmonic distortion, etc.in a testing lab). It's already been discussed that insurance companies and thefederal government frowned highly on these high-horse gorillas that Detroit was pushing in the market, so you can see even further possibilities where the fac- tory would tend to downplay ratings to keep them happy. The insurance companieswould simply jack their rates out-of-sight for a machine with say a 500 horse rating so that sales would suffer very significantly. As far as dyno-testing and horsepower production, the norm for measuring output is done at the flywheel. The motor is entirely self sufficient : it produces its own water circulation, its own spark and pushes its own exhaust. With the measurements taken at the flywheel its easy to see how these hot motors are in fact quite capable of cranking out well in excess of say 600 horses at over 6000r.p.m. However, this is not really practible because you'll never see that manyhorses "on the pavement". This also is not the way the factory measures output.The factory ratings are taken with the accesory belts in operation (power steer-ing, etc.) and through the transmission, to the rear wheels. This was decree'd by law also, in the early '70's. If you look up an engine in Chiltons for say '71 and then look up the same exact motor for '72, you'll find a drop in rating.Not only because of this law however, but they started putting on pollution gad- gets - but in those years it was insignificant. Today of course, these air pumps and emission control devices take a heavy toll on the ratings. So while Jeff bemoans the anemic horsepower ratings of today (as do most Amer- ican auto enthusiasts, myself among them), these ratings are in fact fairly com- parable to the older ratings - it's all a matter of where the output is measur- ed. If you strip off all the emissions equipment, pull the motor and put it on a dyno and measure the output at the flywheel, the gross rating will be right inthe ballpark with the older "pre-emmision" motors - not in the infield, but at least in the park. So when you see a rating of "S.A.E. Net Horsepower: ..." you'll know what they mean - key word: net. Hope this explains a little more on how Detroit arrives at their output ratings. __________ | | ------- --------- /Stuart Lewis / / ssc-vax!stuart/ --------- ------- | | ----------
prophet@umcp-cs.UUCP (05/04/84)
<>
Stuart Lewis mentions in his article about horsepower specifications that the
Federal Trade Commission requires a manufacturer to guarantee that every car
made will at least meet and possibly exceed the rating specified by the manu-
facturer. This is true, but have you ever seen the following:
Prices and specifications are subject to change without notice to the buyer..
This means that a company does not LEGALLY have to deliver the same specs or
even the same engineering design as what is shown in various literature that
manufacturers furnish on their products.
This happens quite frequently in Audio components, but I doubt that it happens
as often with automobiles.
Dennis
--
Call-Me: Dennis Gibbs, Univ. of Md. Comp. Sci. Center.
UUCP: {seismo,allegra,brl-bmd}!umcp-cs!prophet
CSNet: prophet@umcp-cs
ARPA: prophet.umcp-cs@CSNet-Relay