Stroke it six ways

The four-stroke engine is ubiquitous in the cars we drive -- barring Mazda's rotary-powered RX-8 -- but venerable American engine builder and camshaft guru Bruce Crower has created a novel six-stroke engine that's not only claimed to slash fuel consumption, it also runs cooler than a conventional four-stroker.

Crower has reportedly been mulling over the concept for three decades and only recently managed to come up with a workable solution.

"I've been trying to think how to capture radiator losses for over 30 years," he told US publication AutoWeek. "One morning about 18 months ago I woke up, like from a dream, and I knew immediately that I had the answer."

Crower subsequently conjured up a working model, using a small industrial diesel engine as a starting point, and to his surprise, the motor fired up immediately.

The six-stroke engine makes use of an abundant substance -- water. Following the normal exhaust stroke, water is injected into the cylinders and the intake and exhaust valves are subsequently closed. A fifth stroke -- compression -- takes place and the water is converted into steam. The sixth stroke sees the steam being ejected from the cylinders.

Big deal, you might say. But it is, in fact, a big deal because the water injection is claimed to improve an engine's fuel consumption by 40 per cent -- and run much cooler in the process.

"It'll run for an hour and you can literally put your hand on it," Crower told AutoWeek. "It's warm, yeah, but it's not scorching hot. Any conventional engine running without a water jacket or fins (or radiator), you couldn't do that."

Crower says the secret to the six-stroke engine's potency lies in the fact that water expands 1600 times when it makes the transition from liquid into steam. And, due to the water's cooling effect, increased combustion ratios are possible, resulting in improved efficiency and cleaner running.

The biggest drawbacks of the system are fuel vapourisation issues and the fact that an added tank is required alongside the fuel tank to store the water required by the engine (it's said to use as many litres of water as it does fuel).

What are the odds we'll see such an engine in future production cars? Pretty small, according to some industry analysts, but Crower is continuing with his experimentation and development process.