Audi boosts its 1.8-litre turbo
Third-generation engine launches in A4 and A5
- Published in News.
Downsized engine, maximum technology
Direct and port injection plus integrated exhaust manifold increase ratings and cut emissions
Audi's latest 1.8-litre turbocharged gasoline engine is more powerful but more efficient than the unit it replaces. It will be launched in the A4 sedan and A5 coupe but has also been engineered for transverse-engine applications.
The 125kW/ 320Nm unit emits up to 22% less CO2 than the outgoing 118kW/ 250Nm engine and also meets Euro 6. Achieving these targets meant adding a lot of technology, including two fuel injection systems and an integrated exhaust manifold.
Audi's head of inline and V6 gasoline engines, Dr Thomas Heiduk, said: “In order to achieve future emissions standards in terms of particulate number and mass, a dual-injection system is used. As well as direct injection we also use port injection. Port injection is used at part-load, giving lower emissions and better fuel-efficiency.”
The 200bar direct injection system is used during engine start and at high loads for maximum output, but the port injection system offers better mixture formation at part load, minimising particulate emissions. Low injection pressures also mean lower energy consumption.
Efficiency is also improved by Audi's first application of an integrated, water-cooled exhaust manifold. This helps reduce weight and packaging and cuts warm-up times. The aluminium casing is produced by supplier Nemak.
“Integrating the exhaust manifold also means we can do without full-load enrichment so fuel consumption can be significantly reduced,” said Heiduk.
The cooling circuit itself has been redesigned. Thermal management is not through a thermostat but a compact plastic module incorporating the water pump and two mechatronically-controlled sliding valves. Tier One Schaeffler produces the module.
The turbocharger comes from IHI. It's a single scroll design but the manifold feed to the turbine housing is divided in two, reducing exhaust pulse interference. An electric wastegate actuator enables more precise control of boost pressure. Audi's variable valve lift system and a phaser have been fitted to the exhaust cam.
Higher ratings up to 180kW will be developed in future, Heiduk said.
Getting ahead
Aluminium casting developed with supplier Nemak features integrated watercooled exhaust manifold.
