 The cylinder block and other basic structural parts of the engine were jointly developed by the GEMA companies, but the intake and exhaust manifolds, the cylinder head's intake and exhaust ports, and other elements related to engine tuning were independently developed by Mitsubishi.All engines developed within this family have aluminium cylinder block and head, 4 valves per cylinder, double overhead camshaft layouts, and "MIVEC" continuous variable valve timing.All variations of 4B1 engine share the same engine block with a 96 mm bore pitch.