Environmental regulations, in Europe and in the world, place increasingly stringent limits to the consumption and emissions of cars, leading manufacturers to seek methods to improve the performance of our cars. Sometimes these methods are true innovations, but sometimes the solutions can be found by looking at the past, in different sectors. A technology, already used by some manufacturers, is the injection of water in the engine: the idea, already used during the Second World War in different airplanes engines, allows you to lower the temperature of the combustion chamber, especially during the most heavy use, that is, when the engine is stripped more, avoiding the uncontrolled ignition of fuel and allowing you to achieve greater pressure and regimes, thus obtaining more power. The injection of water also allows, thanks to lesser temperatures, to reduce the amount of harmful emissions, such as carbon monoxide and nitrogen oxides (nox), among the major pollutants present in Italian and European urban and industrial areas: also for this reason, this technology arouses strong interest. Nonetheless, the greatest complexity and related costs, together with not brilliant results in the use of more normal and “road” gaits, unlike the speeds achieved in planes, brake the development of systems in cars intended for the general public.
History of the first developments in the skies of Europe in war
The first uses in series of water injection systems, or more often water/methanol mixtures (the simplest alcohol, ch3Oh), they appeared in the aeronautical field, especially in fast hunting engines, already during the Second World War. Both Nazi Germany and the allies began to use this solution to gain maximum power and improve, in general, performance and reliability of their engines.
Especially at altitude, where the rarer air exchanges less heat with the hottest parts of the vehicle, which therefore tend to overheat, it is important to lower the internal engine temperature. In four -stroke vehicles such as petrol engines, fuel is normally set on fire by a spark generated by the candle: if the engine is too hot, however, the air/fuel mixture can catch fire before the expected and in different areas of the combustion chamber, causing serious damage to the various internal components (we speak in these cases of “head in the head”).
By introducing water into the combustion chamber, the latter evaporates rapidly absorbing a large amount of energy (heat) and thus cooling the inside of the engine: once evaporated, the expansion of steam gas adds pressure to the combustive gases. Hunt like the German Focke FW190 or the American Thunderbolt P47D, they already exceeded, in the 1940s, 2000 horses thanks to the water/methanol mixture injections: an increase in power that could be fundamental, during high -altitude fights.
The rediscovery of the injection of water and its disadvantages
In recent decades, some automotive producers have resumed the idea of the injection of water or watery mixtures inside the engine: some of these experiments have become products available on the market, as in the case of the system developed by Bosch in 2016 and mounted for the first time for a street sports car: the BMW M4 GTS.
Thanks to the water injected, the vehicle control unit can avoid sending excess fuel normally used for the cooling of the engine: the manufacturer declares a fuel saving up to 13% during the more “sporty” use of the car.
The smaller temperatures help to obtain a more “clean” combustion: several studies indicate a decrease in carbon monoxide by 40% and nitrogen oxides (monoxide, no and nitrogen dioxide, no2generally indicated how notx) between 40 and 50% in petrol engines, and even up to 85% compared to diesel engines (if used in combination with the recirculation systems of the combustive gases, called EGR).
Despite this, injection systems are still a rarity intended for high -end cars: the diffusion is certainly the complexity and cost of the systems, but also the increase in the risk of corrosion in the systems and in the discharges due to the greater presence of water and steam.
