Thanks to an ultra-rigid crankcase made of lightweight die-cast aluminium (weight: 15 kg), and its compact construction with three cylinders instead of four, the 1.0 TSI - at 89 kg is around 10 kg lighter than a comparable four-cylinder engine. The meticulously implemented lightweight design approach employed by Volkswagen ranges down to the smallest of details. Some examples:
Crankshaft group has low mass and low friction
The crankshaft group - crankshaft, pistons and connecting rods - is distinguished by low moving masses and low friction. The aluminium pistons and forged connecting rods were weight-optimised such that the 1.0 TSI can do without a balancer shaft. The total weight of the crankshaft was also reduced by six per cent by reducing the weight of the crankpins. Four counterweights reduce internal forces in the crankshaft, which in turn reduces loads on the crankshaft main bearings. Very small-sized yet extremely robust crankshaft main bearings and connecting rod bearings make a significant contribution towards reducing friction in the new engine.
Exhaust manifold integrated in cylinder head
Another very high priority item during the development phase was thermal management. The exhaust manifold of the 1.0 TSI has been fully integrated into the cylinder head - that features four valves per cylinder - and fitted with a separate cooling jacket to make the best possible use of exhaust gas energy during the warm-up phase - and to cool the exhaust gases even more effectively at high loads. On top of that, Volkswagen engineers designed a dual-loop cooling system. By using an additional thermostat, the coolant temperature in the cylinder crankcase is regulated to a higher level than in the cylinder head. This offers benefits in terms of internal engine friction, which in turn have a positive effect on fuel economy.
The base engine is cooled by a high-temperature loop with a mechanically driven coolant pump, while a low-temperature loop, powered by an electric pump, circulates coolant to the intercooler and turbocharger housing as needed. The passenger compartment is heated by the cylinder head circulation loop, so that it warms up quickly like the engine.
Small turbocharger, big effects
Thanks to the ingenious design of the exhaust manifold, Volkswagen was able to utilise a compact and lightweight single-scroll compressor with an electric wastegate actuator. This wastegate actuator performs the crucial opening and closing of the bypass valve very quickly. Background: in the low rev range, the bypass valve (also known as a wastegate valve) must be closed in order to drive the turbocharger with the full exhaust gas stream of up to 1,050 degrees C to ensure a consistent build-up of torque. Its maximum charge pressure is 1.6 bar. To reduce losses in the charge changing process in part-load operation, the exhaust backpressure can be reduced by fully opening the wastegate. The engine's responsiveness is improved, because the wastegate actuator is able to regulate the pressure in the wastegate valve very quickly.