Humidity

[J W Hodgson]

The discussions on humidity appear to be based on the assumption that
power output increases with humidity.  This is not supported by many years
of testing and, in fact, engine performance tests correct test results for
humidity and reflect the fact that power goes down as humidity goes up.
Water injection was intended to serve as a means to eliminate knock and
will increase power output on a knocking engine by eliminating the knock
(or if allows more spark advance to be used without knock).  The best
discussion of this I have seen is in Obert's classic text "Internal
Combustion Engines and Air Pollution" on p. 299 in the third edition.

Name:		J. W. Hodgson
Address:	Mechanical Engineering Dept		e-mail: jhodgson at utk.edu
		414 Dougherty Hall
		The University of Tennessee		voice: 	(423) 974-5294
		Knoxville, TN 37996-2210		fax:	(423) 974-5274