Mayflower-homepage.gif” vspace=10 width=120>At the beginning of October Mayflower unveiled its e3 engine concept; an engine that promises great savings in both fuel and emissions. The engine still uses conventional internal combustion principles but in this case it can dynamically vary its capacity and compression ratio to suit the conditions and driver demands. The engine’s inventor, Dr Joe Ehrlich, Formula One Champion Sir Jack Brabham, Mayflower CEO John Simpson, CEO Mayflower Engines Mike Bryant and non-executive director, Rt Hon John Major were there to launch the concept. Mark Wilkinson reports
In this climate of wishing to reduce pressure on natural resources and clean up emissions, many new ideas have been developed to answer these demands. The Mayflower e3 engine, so named for its
concerns, is one of the latest. Most concepts have addressed fuel cells, alternative fuels, improved transmissions, starter motor combined with alternator, low rolling resistance tyres and suchlike. What Mayflower were claiming here was an engine based on conventional principles that could offer a minimum 50 percent reduction in emissions with a minimum 40 percent fuel economy.
What is new is that a pivoted lever arm is used to modify the cycle of the piston in the cylinder. This pivoted lever alters the path of the con-rod big end from a circular motion around the crankshaft axis to more of an elliptical pattern. Because of this, the piston momentarily slows immediately after ignition, so temporarily halting the rapid rise in pressure, thereby allowing the flame front to spread more evenly. Fuel is burnt more completely and so the engine produces more power with lower unburnt fuel emissions. The elliptical path of the con-rod big end also lengthens the intake and expansion strokes, providing for better breathing.
In a conventional engine, at top dead centre, the piston and crankshaft are vertically aligned at the point of combustion, meaning that the initial downward force on the piston is wasted on the crankshaft bearings. The e3 engine’s geometry offsets the big end from the line of the crankcase so that at point of combustion the downward force on the piston is turned immediately into a rotational force.
|A conventional engine’s conrod takes a circular path around the crankshaft axis||In the Mayflower engine the conrod takes an elliptical path around the crankshaft axis|
Besides the above benefits, the most intriguing aspect of the engine is the ability to move the lever arm pivot point – horizontally and vertically – through the use of two hydraulic actuators controlled by the engine management system. If the lever arm pivot is moved upwards, this lowers the position of the piston at top dead centre, thus reducing the compression ratio. A horizontal movement changes the position of the piston at bottom dead centre, altering the swept volume and hence engine capacity. These movements can be carried out dynamically, whilst the engine is running, to instantly alter compression ratio and capacity to suit the conditions. Around town, the engine can run at a low capacity for maximum economy and low emissions; for sporty driving that capacity can be increased to give greater power and torque when needed. The compression ratio is altered according to engine load – high compression for maximum energy extraction at low loads; low compression for high loads (sporty driving) without knocking. Fixed compression ratio engines are limited to the highest ratio at which they can function under high load without the danger of knocking. Under low load, the possibility of knocking is much lower, so that a higher compression ratio can be run safely. Engine capacity of the show engine could vary up to 20 percent, from 1.4 to 1.7 litres for instance. Compression ratio could vary from 9:1 up to 15:1 for example.
Techniques and technology aside, Sir Jack Brabham said that the company plans to follow this with a diesel version of the engine. The engine crankcase (petrol or diesel) would need some remodelling to fit the oscillating lever arms. The lever arms and new bearings would also need to be developed. The engine management system would have to be programmed to control not only the ignition, but also to activate the lever arms quickly and accurately to match engine demand.
|The crankcase would need to be slightly redesigned to accommodate the Mayflower engine’s pivoted lever arms|
When I asked Mr Brabham about the cost of all this development, he said that the beauty of the concept was that if all the principles were fully utilised, then an e3 engine would be able to run without the secondary catalyst that future emissions regulations would demand. That way, he said, the engine could be produced and supplied for little over the cost of what it would be to produce a conventional engine. No new production technologies would be needed. The big rider to those brave claims at the beginning of the article however, is that these will only be achievable “if all features of the technology are utilised, including downsizing”, which refers to the use of the engine in its smaller capacities (say the capacity is variable between 1.4 & 2.0 litres, in this case it would be running at 1.4 litres). The company pointed out however that those claims were made without the benefit of other technologies, such as turbocharging, supercharging, direct injection or variable valve timing, all of which would be compatible and could provide further improvement.
The petrol model on display was a single cylinder unit that has been used for testing and demonstration purposes. For on-road testing the company will need to build a multi-cylinder version. One would have naturally expected that those oscillating lever arms would be a new source of vibration, but Mr Brabham said that potential customers had been pleasantly surprised by how quiet and smooth the single cylinder version was. A company source also said that the lever arms would be built significantly smaller and lighter than on the show engine – when production-optimised for a particular engine they would not be a major addition to the size of the crankcase for instance.
Mayflower has so far invested £6m to acquire 33 percent of the rights to e3; it has the option to spend another £33m to increase that to a controlling 51 percent. There are other technologies already signed up for production to improve fuel economy and emissions as an add-on to the engine; this is one of the first engine concepts to show such potential. Saab‘s variable compression engine could be seen as a competitor but that uses a tiltable engine block and is only able to vary its compression ratio, not its capacity. However, that engine has achieved excellent results with downsizing and high pressure supercharging. Mayflower intends to make its money from the sale of development and production licenses – with a global market for suitable engines of 160m units a year it is sure to recoup its investment. The company hasn’t sold a license yet, but a spokesman said on 16th October that the engine was enjoying great attention from the engine and car makers; “flying in from around the world to see it”. It will be 18 months before the e3 engine is installed in a car for test – and a possible three years after that before it reaches the market. There are a lot of people out there that can’t wait to try it out!