07 Aug 06 16:47
Engines that combine the efficiency and torque benefits of a diesel engine with the smoothness and low emissions of a petrol unit, are five years away from mass-market production, according to a report in AutoWeek, with General Motors planning to have an HCCI prototype up and running by next year.
Homogenous-charge compression ignition (HCCI) technology is described by AutoWeek as 'the next big evolution of the internal combustion engine'. It works in both diesel and petrol engines, and is cheap to produce and fit - engineers claim that an HCCI petrol engine can deliver similar fuel economy to a comparable diesel, but at much lower production costs. This is because emissions of harmful particulate matter are effectively eliminated within the cylinders, as fuel ignition is much more efficient, and thus there is no need for expensive catalytic converters or particulate traps.
In a petrol HCCI engine, ignition can take place by the compression of air and petrol within in each cylinder, as in a diesel, rather than via a spark plug. In a diesel HCCI engine, a glow plug can be used in a similar way to a spark plug. However, the engines do not run in HCCI mode all the time: they switch into this operation when under relatively low demand, such as cruising at highway speeds, and fire up in a conventional fashion the rest of the time.
Obstacles to overcome are said to include noise and vibration, as HCCI mode is not as quiet and smooth in a petrol engine as spark-ignition. Engineers are also working to perfect an even ignition of fuel in the cylinder and on monitoring air temperature and the direction in which the fuel is sprayed (via direct injection) into the cylinder.
AutoWeek reports that HCCI engines are 'at least five years away' from becoming a full production reality, but says that Volkswagen, Toyota, Ford and Nissan are all working on HHCI engines as well as General Motors.
A Ford engineer told the magazine: 'We believe that the HCCI gasoline engine could deliver a substantial incremental efficiency benefit that could close the gap between gasoline and diesel engines.'
A Toyota spokesman added: 'In Toyota's research centre, the HCCI and fuel cell departments are in competition to be first.'
