Engine block: Pistons
The light alloy pistons have grooves for two compression rings and one oil scraper ring. The upper compression ring is plane type and nitride hardened. The lower compression ring is phosphate coated and has oil scraper properties. The oil scraper ring is in three parts and nitride hardened. The pistons are tin plated and the gudgeon pins nitride hardened. An arrow on the piston crown indicates the position for fitting (arrow pointing to camshaft drive end). It is essential that the pistons are fitted correctly because the gudgeon pin hole is offset 0.8 mm towards the exhaust side. This has been introduced to reduce the negative effect of axial forces on cylinder wear. The pistons are cooled from below with oil sprayed through a nozzle fitted in the bottom of the cylinder block.