General Motors will launch a new, downsized direct injection 1.4 turbo engine in 2010 that will be offered in a wide range of models including the Vauxhall Astra, Corsa, Zafira and Insignia. It develops between 120 and 140bhp, and is claimed to provide the performance of a 1.8-litre engine with a 10 per cent fuel economy improvement. Direct fuel injection into the combustion chambers, variable cam timing of both inlet and exhaust valves, turbocharging, reduced internal friction and the lower overall weight of the engine all contribute.The chance to try a development engine in an Astra at a recent press event revealed a very lively performer - peak torque occurs at just 1850rpm - excellent refinement, the 1.4 revving very smoothly to the limiter and generally good throttle response. Slightly slow pick-up in high gears below 1800rpm is our only criticism of this otherwise impressive power unit.GM also demonstrated an early HCCI (Homogeneous Charge Compression Ignition) engine in a Vectra. HCCI engines promise the potential of combining the emissions cleanliness of a petrol engine with the fuel consumption of a diesel, by operating under compression ignition during light to moderate engine loads, and spark ignition when cold and during heavy load demands.An HCCI engine is up to 15 per cent more economical than today’s equivalent power unit, but presents major challenges in terms of controlling engine knock, as well as the transition from one combustion mode to the other. As installed in a Vectra this experimental HCCI engine produced the kind of diesel knock experienced in the rougher diesel cars on sale 20 years ago, as well as a low rev hesitancy that made the car easy to stall and the odd stutter as the engine transitioned between compression and spark ignition. But this is a very early engine, and the Vectra was unaltered in terms of NVH. GM is publicly talking of HCCI engines for 2015, but privately senior engineers say they are aiming at an earlier date.Mercedes is also developing HCCI engines under is DiesOtto programme, while VW believes that this combustion system needs synthetic fuels to run effectively, its engineering vehicles largely free of transition hesitancy as a result.
Richard Bremner
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