The Nissan MR engine family consists of straight-four 16-valve all-aluminium automobile engines with variable valve timing co-developed by Renault and Nissan. Renault calls it the M engine. Other noteworthy features of this engine family include acoustically equal runner lengths and a tumble control valve for the intake manifold, a "silent" timing chain, mirror finished crankshaft and camshaft journals, and offset cylinder placement in an attempt for increased efficiency.