Over the past few months, Motoring Weekly has published articles about different technologies and configurations to improve the internal combustion engine – something that we at MW Towers think still has plenty of life in as Governments argue and make ill-judged decisions about moving to electric power.
Recent articles have included the cam-less engine, Mazda considering the return of the rotary engine as a range extender and even repackaging of existing technology by Delphi to extract more power and fuel efficiency. Not many people know about the moment-cancelling engine that the famous racer, Dan Gurney, developed with a small team. Gurney, who died earlier this year, had a long and very successful racing career in single-seater and sports cars and was a gun engineer, so knew a thing or two about how to extract the most from his machines!
The engine that his team developed was called the MC4S (Moment Cancelling Four Stroke) and was designed as a two cylinder motorcycle engine. The focus was reliability, efficiency (more power) and less emissions. The core change that the team made to a traditional engine was that there were two crankshafts – one for each cylinder. Each one rotates in the opposite direction of the other and that helps to solve one of the big issues with any piston motor: balance. A motor that is out of balance vibrates and vibrations cause material wear and failures thanks to the stresses put on them.
In a traditional engine, the crankshaft runs the length of the engine, whether it is a straight or “V” configuration, such that all pistons are connected to the one shaft. Sometimes a smaller balancing shaft is required to smooth out the engine. With the Gurney motor, the crankshafts are mounted perpendicular and geared together to enable the counter-rotation of the pistons. With that design, the camshafts are also in the same configuration meaning that they are also smaller and therefore lighter.
Interestingly, having two crankshafts is not a new idea for a motorcycle engine – they were used in the 1930s on some British motorcycles and the Japanese manufacturers used them in the 1970s on racing machines. It seems that the very first use was by Bugatti in their U configuration aeroplane motor, albeit much bigger than a motorcycle one! There are very few really new ideas in the world today, old ones are just repackaged, maybe with new materials used in the construction.
Internally, the engine has a couple of features that help the design. The first is that the conrods are shorter than normal and the piston bore is larger than the stroke making it an over-square motor. The intake ports have been designed to increase the pressure of the air flow and the prototype used twin overhead cams and four valves per cylinder with a capacity of around 1800cc – similar to the size of a Honda Goldwing.
What Gurney’s team also did was to really research the intakes to get the flow as efficient as possible. They were able to get an 85% increase in efficiency simply by understanding how to get the fuel/air mix into the cylinder in the most efficient way possible. This was without applying more technology such as a turbo or supercharger. The patent that the team registered had plans to upsize the motor to use four, six or eight cylinders with odd numbered pistons on one crankshaft and even numbers pistons on the other.
Not much has been reported about this motor since Gurney died in January, although they were supposed to be testing it during 2017. Perhaps we will see these ideas appear in the near future if someone can licence the patents and get them into production. If the prototype had a capacity of nearly two litres from a twin-cylinder, then careful engineering might get us a super-powerful four or six cylinder for racing or road use.
I like these stories because they show the ingenuity of humans and if many of the ideas could be combined, the world could see them in production in a wider variety of uses.
Image source: New Atlas.