He invented the electromagnetic transmission, introduced in the Owen Magnetic of 1915, and was a pioneer in the early automobile industry.
During the 1890s, Entz became fascinated with the development of the automobile, and by 1897 he was working as a chief engineer at the Electric Storage Battery Company in Philadelphia, Pennsylvania.
It was while working for the Electric Storage Battery Company that Entz designed a gasoline-powered automobile with an electric drive transmission, and this was built as the prototype Columbia Mark IX by the Pope Manufacturing Company.
On the vehicle's test run, driven by Hiram Percy Maxim, an electric spark ignited fuel in the gasoline tank and destroyed the car.
Justus Entz was altogether granted 75 patents in automotive engineering.