US company touts new motorbike engine as one of world's cleanest

US engineering company Avadi has come up with a new single four-stroke piston engine that runs without valves and is as frugal on fuel as a diesel.

At 42%, the Avadi MA-250 engine has an efficiency on a par with the best current diesel engines, even though it burns petrol.

"We've spent years re-imagining internal combustion engine design and have now developed and successfully patented one of the most fuel-efficient, lightweight and forward-thinking engines in the world today," Avadi says on its website.

"Our vision is to advance a proven technology and create a family of lighter, smaller, eco-friendly engines that will help to create a cleaner, better world."

The prototype Avadi is a 250 cc engine that produces 30 Nm of torque at 3,500 rpm and 15 horsepower at 3,700 rpm. That sounds meagre, and compared to current water-cooled 250 cc engines with around 25 hp, it is.

However, these engines rev 5,000 rpm higher for the power and only generate 20 to 25 Nm at twice the speed of the Avadi. The Avadi MA-250 consumes significantly less petrol for the same power. It also reportedly weighs only 11 kilos.

With this performance, the Avadi engine is ideal for small motorbikes and scooters, delivery vehicles or as a range extender in electric cars.

The fuel savings are made possible by three factors: the low friction of the piston in the cylinder and lack of conventional valve train with camshafts, springs and valves, which eliminates further friction. This normally consumes a lot of engine power, especially at low engine speeds in conventional engines.

Also due to its low engine speeds, it does not need water cooling or an oil pump, which further reduces the number of moving parts and friction losses. Lubrication is provided by centrifugal force.