 The Type 4 engines were considerably more robust and durable than the Type 1 engines, particularly in Transporter service.The engine that superseded the Type 4 engine in the late 1983 VW Bus retained Volkswagen Type 1 architecture, yet featured water-cooled cylinder heads and cylinder jackets.The wasserboxer, Volkswagen terminology for a water-cooled, opposed-cylinder (flat or 'boxer engine') was subsequently discontinued in 1992 with the introduction of the Eurovan.