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From: tron@fluke.UUCP (Peter F. Barbee)
Newsgroups: net.auto
Subject: Re: engine revvs and fuel economy
Message-ID: <662@vax1.fluke.UUCP>
Date: Mon, 18-Jun-84 11:09:50 EDT
Article-I.D.: vax1.662
Posted: Mon Jun 18 11:09:50 1984
Date-Received: Thu, 21-Jun-84 01:50:07 EDT
References: <148@pertec.UUCP>
Organization: John Fluke Mfg. Co., Everett, WA
Lines: 25

Two statements about fuel economy:

1) Thermodynamics tells us that an IC engine is most efficient when
   operating at maximum torque

2) A study done by Porsche about 4 years ago showed that all of their
   cars got their best mileage when driven in high gear such that they
   were almost lugging.

At first glance these 2 statements appear contradictory because no
engine develops max torgue just above lug speed but they're not.
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.

				Peter Barbee

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