When cars first appeared there were many different technologies all fighting to become dominant and over the first real decade of the cars life, many technologies were superseded or were developed further to make them successful. One area that had it’s fair share of technological advancement quickly was the engine – clearly this was the way that the car was powered so anything that could prove to be more reliable and deliver a decent power output was going to win.
The modern engine started to come into being in the mid 19th Century when Italian engineers, Eugenio Barsanti and Felice Matteucci patented a 4 stroke engine in London which was originally designed to be used by ships and machines. Nicolaus Otto, a German engineer took the 4 stroke cycle and applied it to an engine that used the 4 stokes together so that they complemented each other. This patented design became the basis of all 4 stroke internal combustion engines due to its efficiency.
The Otto Cycle is made up of the 4 stokes of a piston, namely down (suck in mixture, originally coal-gas and air), up (compression), down (ignition & power stroke) and finally up to exhaust the burned gases. Otto was also one of the first to use a spark plug to ignite the mixture in the cylinder.
Otto was a part owner and founder of Deutz and he employed Gottlieb Daimler and Wilhelm Maybach. Both of the engineers worked on the Otto Engine before moving on to greater success with their own manufacturing company. Incidentally, Ettore Bugatti also worked at Deutz too before he made his name elsewhere! Deutz is still in existence making truck and other engines.
The Otto Engine and subsequently all other car engines are known as adiabatic engines – in other words they do not use the heat from the power stroke – this is typically lost through the block and the exhaust pipe. The power of the engine is derived by converting the ignition of the mixture to a circular motion through the crankshaft to power the wheels. So, because there is an explosion in a small space, heat is generated and lost – in fact the heat is so great that air or water is typically used to dissipate this heat, which is lost and not used as energy.
A few years after Otto and his team had developed the Otto Engine, James Atkinson, a British engineer developed the Atkinson Cycle Engine. This took the 4 stroke concept from Barsanti and Matteucci and then developed an engine outside of the patents owned by Otto. This resulted in a much more efficient engine but produced less power.
Atkinson did this by leaving the intake valve open longer and using a low compression, he found that more energy was produced from the ignition that was converted into mechanical power. So, because he used less air than Otto, he got less power but the 4 stroke cycle was completed in just one turn of the crankshaft as opposed to two on a single cylinder engine by connecting the conrod to a set of levers that were connected to the crank. The levers moved in a way that meant that the strokes were of different lengths – the power stroke is longer than the compression stroke.
But Atkinson had the last laugh! Although the Otto Cycle became dominant for most of the last century, engineers were very interested in the Atkinson Cycle. For example Ralph Miller used the concept to produce the Miller Cycle, which was used by Mazda/Eunos in their cars in the 1990s and recently by Subaru.
The Atkinson Cycle is used extensively in hybrid cars such as the Toyota Prius as it uses less fuel than the Otto Cycle. In fact the Atkinson Cycle is at its most efficient when used with a supercharger or hybrid motor.
And finally, talking of heat loss from the Otto and Atkinson engines, companies like BMW are looking at using some of the heat of the power stroke to generate more power by transferring that heat to another energy source. So in the future we will see engines that use Otto or Atkinson Cycles that are even more efficient as the heat generated will be used to generate power, probably in the form of an electric current that charges a battery or runs the cars electrical system thus reducing that load off the core engine which will then increase the available power to the wheels. Look out for more technological advances on this 120 year old foundation!