Nissan MR Engine

Nissan MR Engine

The MR is a family of straight-4 all-aluminum 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 for an attempt in increased efficiency.

The MR engine family features 'under stress' manufacture, meaning while the block is being bored, a torque plate puts the block under stress. The block becomes temporarily distorted until the head is torqued onto it, at which point the block is pulled into the correct shape. This method is unlike traditional engine assembly, in which the head being bolted to the block can twist it out of shape, decreasing engine efficiency and in the worst case scenario, increasing oil consumption.