Achates spends $125 million on new two-stroke

An executive of Achates Power Inc. has revealed the company has invested $125 million developing a new two-stroke engine that uses compacted graphite iron (CGI)  for its highly-stressed cylinder block.

What is the future for, and of the automobile? The US Society of Automotive Analysts (SAA) attempted to find answers to that question last month at the appropriately named ‘The Gem Theatre’ in Detroit, a city which has undergone serious structural changes following the decline of the motor industry in motown.

The SAA suggests that for the automotive industry it is not ‘business as usual’.  That outside forces, new technologies and new entrants into the industry are forcing OEMs and suppliers to rethink how they do business.

Among ‘new’ technologies unfurled at The Gem was the opposed-piston engine from Michigan-based Achates Power Inc. But this is not so much a ‘new’ technology as an up-to-dated variation of an old theme, as indicated by David Johnson, president and chief executive officer of Achates Power when he put up a slide of a Napier Deltic engine of 1960 vintage – 50 years ago. The German Luftwaffe (air force) used Junkers' two-stroke, opposed-piston technology in World War 2 aircraft!

Johnson, before revealing a few details of his ‘new’ engine gave some pointers regarding new technologies. As to electric vehicles he suggested that the heaviest vehicles are unlikely to be battery-powered; that for electric vehicles ‘cruising distances are so short and charging times so long that they will need new battery technology’; and that batteries ‘cost too much and take up so much space’.

He added that fuel efficient technologies being developed by the automakers are not being taken up by consumers, yet as vehicles last longer fuel efficiency will become even more important. He added that huge expense is being directed to develop electric and hydrogen fuel cell vehicles, whereas in places like India, electricity (meaning electric vehicles) is not going to work.

As to the Achates opposed-piston two-stroke, Johnson claims the engine is 34 per cent lighter and could cost 12 per cent less than a conventional reciprocating engine.

According to Johnson, Achates Power has invested $125 million on developing the engine since 2004. There was no mention in his talk however of one partner – Cummins Inc. – and a Department of Energy research programme.

Johnson claims also that dynamometer hours now total over 7,000 and tests show the engine to be 60 per cent more efficient than a gasoline engine and 20 per cent more efficient that a diesel.

“We have the data to show this,” Johnson told his audience.

He claims measured tests show that a 4.9-litre engine has a best-point thermal efficiency (BTE) of 44 per cent. As to oil consumption, one notorious drawback of earlier two-stroke engines, Johnson pointed to a figure of 0.1 per cent fuel specific oil consumption.

From an engineering viewpoint Achates Power, like other developers of this type of engine, are using compacted graphite iron (CGI) to gain cylinder block strength.

Engineers have noted in a paper on Multi-Cylinder Modular Development Engine that “the A48-3-16 shares most of the power cylinder with the A48-1 and in an effort to reduce the development schedule, many components are compatible. Similar to the A48-1, the A48-3-16 is designed for a peak cylinder pressure of 200 bar with overload conditions of 220 bar. The block was cast from compacted graphite iron (CGI)”.

Just when the Achates Power opposed-piston engine rolls onto the production line remains to be seen. But developers have to have deep pockets and long timescales for new technologies like this.

As we have seen from promises made in China in recent years, opposed-piston engines can take longer to emerge than first planned. And, as development of the Wankel engine has proved, some new engine technologies take a long time to evolve - and some never make it at all. 
It is 60 years since the Wankel emerged at the Frankfurt Motor Show; almost the same length of time since the first UK automotive gas turbine took to the roads, and automotive Stirling engines were being proclaimed in the US. History has shown that not all roads are paved with gold.