...However, a 3-cylinder engine was out of the question for a fuel consumption level of just one litre per 100 kilometres. A 2-cylinder engine was also quickly dismissed. The final solution was a one-cylinder naturally-aspirated diesel engine with a displacement of just 0.3 litres. The direct injection diesel engine makes use of the most efficient injection system available today: a unit injection element with 6-hole jet and pre-injection. It provides a high working pressure of 2,000 bar.
The one-cylinder SDI engine in the 1-litre car is not a mere derivative of the familiar engines, but is rather a completely new, technically highly sophisticated development. Two overhead camshafts actuate roller rocker fingers which in turn actuate three valves, two inlet valves and one exhaust outlet valve. These are then fed from the engine through a titanium exhaust system with reduced backpressure.
The two overhead camshafts are driven by a strengthened toothed belt. The engine is an aluminium monobloc construction. That means that the cylinder head and crankcase of the compression-ignition engine are cast as a single piece. But that is not the end of the lightweight construction, for also here, all technically feasible stops have been pulled. The fuel pump housing is made of magnesium. The trapezoidal connecting rod is made of particle-reinforced titanium. The success of these measures becomes evident on the scales: dry (i.e. without operating fluids like oil and water), the engine weighs in at an unbelievably light 26 kilograms. Ready for operation, including the starter-alternator, it is just 12 kilograms more.
Besides the reduction in weight, various measures were taken inside the engine to optimise fuel consumption. To minimise frictional resistance, the running area of the cylinder has been laser alloyed, roller rocker fingers reduce friction in the valve drive, even the tension of the piston rings has been reduced.
The centrally mounted one-cylinder SDI diesel engine is transversely installed in front of the rear axle, has a displacement of 299 cc and generates its maximum output (6.3 kW / 8.5 bhp) at 4,000 rpm. The maximum torque of 18.4 Newton metres is delivered at 2,000 rpm.
Even with this apparently low output and power development, the extremely light vehicle weight (which is comparable to that of an average touring motorcycle) and the excellent aerodynamics (with a drag coefficient of 0.159 ? much better that a motorcycle and far better any series production vehicle) provide for a lively performance. For example, the 1-litre car reaches a top speed of 120 km/h.
