Extra Openings
Union Pacific GP9 No. 261 sits at North Yard in Salt Lake City, Utah the afternoon of March 24, 1979. In April 1956, UP 261, 281, and 185B were equipped with AiResearch Model T-30 turbochargers. To improve performance, UP 261 and 281 received 20" x 20" openings along the carboy doors for additional cool air to feed the intakes. Tests showed overall performance benefited from the openings, but a less expensive rooftop design was adopted. Even though the turbocharger was removed in 1962, UP 261 retained the extra door opening holes until retirement from the roster in 1981. History from UtahRails.net.
Extra Openings
Union Pacific GP9 No. 261 sits at North Yard in Salt Lake City, Utah the afternoon of March 24, 1979. In April 1956, UP 261, 281, and 185B were equipped with AiResearch Model T-30 turbochargers. To improve performance, UP 261 and 281 received 20" x 20" openings along the carboy doors for additional cool air to feed the intakes. Tests showed overall performance benefited from the openings, but a less expensive rooftop design was adopted. Even though the turbocharger was removed in 1962, UP 261 retained the extra door opening holes until retirement from the roster in 1981. History from UtahRails.net.