Shortly after it's birth, the combustion engine had to assert itself against the steam engine and the electric-motor drive. The first wave of the performance explosion only came after 1900 with the rapid increase in cubic capacity. Although one was not yet capable of casting four cylinders in one piece, indeed the biggest engines already reached a total displacement of 20.000cc (20 liters). Herewith, speeds of over 200 km/h were achieved, e.g., by the 1909 Blitzen-Benz. Fiat also had examples of this sort. The revs. continued to be modest, a good bit below 2.000 RPM.
If you are of the opinion, that high revs are necessary to achieve high speeds, here, for the first time, you have to make a distinction. The second big performance offensive can be dated back to the 1920s. At that time, Paul Daimler, ( the son of the famous Gottlieb) who was the construction director of the Daimler-engine-works, initiated the era of the compressor engines. His successor, Ferdinand Porsche, advanced them to mass production- and readiness for racing. In the 1930s, together with the abundant flow of money from the Nazis, German racing cars (incl. Auto Union) achieved an incredible dominance. The speed record now was way over 400 km/h.
The actual cubic capacity had been reduced to approx. 6 liters, whereby the engine speed, in the meantime, had been increased to a good 5000 RPM. You probably knew all along, that particularly high torque, can also be achieved by charging the engines. Besides, basically the piston-engine doesn't care where the pressure comes from. At that time they had screaming compressors, nowadays, it's turbo-chargers or their combination with compressors.
One can of course, achieve high performance through respectively high revs, however, the torque is also then only developed when high revs are reached, which makes the engine not ideally suitable for everyday use. Nowadays, engines like this have so much power, that the torque, even at very low revs, is far higher than that of the average motor car. Earlier, it was nigh on impossible to plod along behind a tram in a souped-up sports car. One would simply break down, because of sooted- or oiled-up spark plugs.
Now, it's about time we explained the mysteries of the displacement cubic capacity (cubic capacity). The displacement is the volume determined by the bore and the stroke of the engines cylinders, whereby, the latter is not at all happy with very high revs. For a long time an average piston speed of 16 m/sec. was considered to be a sort of ceiling, before the engine life was endangered. In the wake of infinitely better technology, this limit has now been set at 25 m/sec. In the beginning this was only valid for the Formula 1, in the meantime, it is also achieved by the Lamborghini Gallardo LP 540/4. In Formula 1 the peak revs of 19.000 RPM have, in the meantime, been reduced.
After the middle of the last century, Alfa Romeo managed, with great success, to mass-market the twin cam engines, indeed, they were even installed in light delivery vehicles. If one takes a closer look however, their RPM, despite the advanced valve control, were not that high at all. The Japanese, with their reputation of being passionate tinkerers, were the first ones who managed to produce an astonishingly durable engine which was capable of really high revs. It did not begin with the Honda S 2000, but much earlier with the 360 to 800 series.
Herewith then, a further 'rule of engine technology', that high revs shorten the life of the engine was refuted. Thus, the advancement goes on, right up to today preceptions are being shattered, e.g., for a long time, the phrase, 'nothing can replace capacity, except more capacity' was considered valid. This statement also has to be re-thought, because modern downsize engines with turbo- and Roots chargers working together easily compensate for the weaknesses of small displacement engines.
For a long time, a longer stroke, in relation to the bore, was an indication of the pulling power of the engine and was also seen as a characteristic of the Diesel engine. This phenomenon is also beginning to disappear. If, right now, you are studying the nearing of the bore and stroke dimensions in the modern Diesel engine, have a look at the (geometric) compression, through charging, the compression ratio is becomming less and less. In the past, the compression ratio of the Diesel was always higher, soon, the Diesel- and the petrol engine will both have a ratio of 14:1.
The only remaining characteristic exclusive to the petrol engine, is the electric ignition. Indeed, having a look at the development, there are already petrol engines, which, in certain operational areas, can do without it. The petrol engine virtually becomes a self-ignitor. With modern engine management, another rule which can be refuted.
Thus, high revving aspiration engines generally require more valves and charged engines, rather fewer. For many years, the individual cylinders in sports car engines had only small displacements, a greater number of cylinders was preferred. The 1950 Formula 1 Ferrari was the famous 12-cylinder with a total capacity of only 1,5 liters. There are also alternatives to this development. Porsche, of all companys, certainly born out of necessity, produced a 3 liter engine with only four cylinders for their 968.
I myself, have believed for a long time (and still do today), that the Diesel engine is completely unsuited for motorcycles, until I found out that there are (or were) Diesel motor-bikes being produced and sold in India. Somewhere in the world there always seem to be (self-appointed) developers, who want to mass-produce things that the world has never seen before, regardless of whether they make sense or not.
Indeed, there is also a great deal of pressure from the outside. The 1974 exhaust gas regulations have changed our engines, although more in the peripheral sense. The currently existing CO2 restrictions reach deep inside the engine. Who would have thought, ten years ago, that four valve- and Diesel engines would be an option. In the meantime, the long stroker is not frowned upon because of it's incapability to produce high revs, but because of it's greater friction.
As far as motor vehicles are concerned, one should never say never! Not so long ago no-one would have invested even one cent in the development of rotary- (Wankel) or two-stroke engines in the four wheel branch. Recently, at Audi, the rotary engine can be found as a Range extender, to be used when the high voltage battery has run down. Let's wait and see what the consumption figures look like.
What about the two-stroke? My opinion is that it will come, when, through downsizing, as Fiat has already done, one arrives at a two-cylinder engine. The much quieter crank mechanism and the direct injection are forcing the developers to react. No, this has nothing in common with the Trabant, except perhaps, the front-wheel drive.
Because will probably have to keep on waiting for an everyday- and holiday-suitable electric drive train, the combustion engine still has a chance. After all, as something really new, it can now also store energy in the shape of compressed air (ETH Zürich)-(Swiss Federal Institute of Technology), or it can dazzle us, like in the variable compression engine from the MCE-5 Company (see video) with almost unbelievable performance-, torque and consumption figures. Altogether, the trend is towards less- and smaller cylinders, indeed, the amount of components surrounding them is increasing and they are getting larger and larger. 07/11