sentences:  This first vehicle was followed by a small batch of three improved vehicles that were evaluated by the armed forces in 1956–1957.The improved vehicles were powered by a new, horizontal six cylinder diesel engine, the YaMZ-206V, instead of the original V-6 of the PT-76.In 1958, the order to start series production of the SU-85—as it was initially known (although there was already a vehicle with that same name, based on the T-34)—was given.