The valvetrain consisted of 12 poppet valves timed by two chain-driven overhead camshafts. Piston engines normally use valves which are driven by camshafts. The N1 engine also has upgraded camshafts and upgraded turbochargers. It featured twin overhead camshafts and four valves per cylinder. The M104 featured dual overhead camshafts and four valves per cylinder. It has four valves per cylinder, overhead camshafts, and shim over bucket valves. These engines all came equipped with roller camshafts & lifters. It had four overhead camshafts and twin carburettors. It has four valves per cylinder, overhead camshafts, and shim-over bucket valves. A central gear tower drove the overhead camshafts, superchargers and ancillaries. In normally aspirated form, it produced from dual overhead camshafts and four valves per cylinder. This engine is an all-aluminium construction with double overhead camshafts and a flat-plane crankshaft. The Dual VVT-i system adjusts timing on both intake and exhaust camshafts. It is an all aluminium five-cylinder engine with 20 valves and double overhead camshafts. Both engines have timing belt driven camshafts.