It is a six-stroke engine cycle, producing two power strokes for every idle stroke, which promises more power and torque with greatly reduced consumption and emissions. Lotus and Bosch are each working on six-stroke engines and say they will also allow car companies to use much smaller, lighter engines to combat ever-rising vehicle masses. Critically, they use a variation on current engine layouts which means they can be mass produced in existing factories.

Bosch is already running a single-cylinder test engine and believes a six-stroke could be in production within six years, but will not make any official confirmation.

Lotus Engineering has been more open. Technical director Simon Wood insists its engine will be a major force in curbing greenhouse gas emissions and provide V8 power from four-cylinder engines.

The six-stroke systems use radical cylinder-head and valve technology and, after the traditional power stroke, minutely re-open the exhaust valves to reintroduce short-lived oxygen free radicals which ignite the last power stroke. And the ignition is much more precise than a spark plug, Wood said. ``Our engine doesn't need a spark plug,' he said. ``The oxygen-free radicals ignite the extra charge of fuel without a spark, so it's essentially dieseling on the last power stroke. ``It's very simple, actually, and you get more power and more torque and fewer emissions for free.' Oxygen free radicals, a by-product of normal ignition, remain free for only milliseconds and are normally exhaled directly out of the exhaust manifold.

Lotus developed a tiny version of its hydraulically controlled active-suspension system to open and close all the engine's valves, ending reliance on timing chains, camshafts and cam lobes while ensuring valve openings are far more precise. The change also means an engine will be lighter, with smaller overall dimensions for similar capacities.

While two major carmakers are believed to be funding the Bosch development, Lotus is working closely with heavy-duty engine maker Eaton, in the belief six-stroke engines will see production first in tractors and heavy trucks.

The increasing similarities between petrol and diesel engine hardware has Lotus believing six-stroke engines in passenger cars and even sports cars is just a matter of time. ``Petrol and diesel engineering is definitely merging,' Wood said. ``It will arrive at the point where it is no longer the mechanical engineering that will be important, but the chemical engineering.' So he said petrol companies could be forced to develop a fuel between today's unleaded and diesel.

Source: Northern Territory News