With a soft sigh of the piston, the brass-barred doors closed behind Chaff.
"The Story of Louie"
Oliver Onions
Mixture is compressed into smaller volume by piston moving upward.
"The First Airplane Diesel Engine: Packard Model DR-980 of 1928"
Robert B. Meyer
Combustion heat increases the cylinder pressure forcing piston downward.
"The First Airplane Diesel Engine: Packard Model DR-980 of 1928"
Robert B. Meyer