Feature
Nikasil: Friend or Foe? Words – Jeff Heywood / Images – BMW Press
BMW E34 540i
To motorists of a certain age, the word Nikasil is as scary as a Siberian labour camp. Back in the ‘90s, engines with Nikasil-coated cylinders suffered excessive bore wear. A batch of petrol was the culprit and it destroyed engines, many of which were built by BMW. The controversy tarnished BMW’s reputation, but quite a few automobile brands suffered cylinder bore wear problems, too. But who or what was to blame exactly? Nikasil History - Nikasil was a coating introduced by Mahle in 1967. It was initially developed to allow the apex tip seals in Wankel engines (most notably in the NSU Ro80) to work directly against the aluminium rotor housing. Before Mahle’s innovation was implemented, the tips in the rotary engine were renowned for wearing and letting oil pass by the seals. NSU struggled with this issue and it led to VW taking over the brand in 1969, as the compensation claims were crippling the small company. Mahle’s Nikasil coating allowed aluminium cylinders and pistons to work directly against each other with low wear and little friction. Unlike other methods, including cast iron cylinder liners set into aluminium blocks, Nikasil allowed very large cylinder bores with tight tolerances and thus allowed existing engine designs to be expanded easily. The aluminium cylinders also gave a much better heat conductivity than cast iron liners, an important attribute for a high-output engine. This is why the coating was further developed as a replacement
40 BMW Car Club Magazine September 2021
Well known German automotive parts supplier Mahle introduced Nikasil back in 1976, principally to help stop the wear on seal tips in rotary engines, which was a blight on NSU and their excellent, modern looking Ro80, Car of the Year in 1968 but hamstrung by a wonderfully smooth but oil burning Wankel rotary engine…
for hard-chrome plated cylinder bores for Mercury Marine Racing, Kohler Engines, and as a repair replacement for factorychromed snowmobiles, dirt bikes, ATVs, watercraft and automotive V8 bores, and it is still used to this day in top line racing applications; F1 and IndyCar engines use Nikasil extensively. Suzuki also uses a nickel phosphorussilicon-carbide proprietary coating
trademarked SCEM (Suzuki Composite Electro-chemical Material) – a techoogly not dissimilar to Nikasil – to maximize cylinder size and improve heat dissipation in the Hayabusa range of engines, which are also used in automobile and racing installations. Nikasil is short for Nickel Silicon carbide. Silicon carbide is a very hard ceramic (much harder than steel) that can be dissolved in nickel. The nickel solution can then be electroplated onto the aluminium cylinder bore. The piston
Porsche’s Motorsport engine builders used Nikasil widely in the venerable 917’s amazingly powerful flat-12 engine www.bmwcarclubgb.uk
