Since the dawn of time, the humans have a desire to be better and faster than others. This calling is not only the nature of humankind, but also the driving force behind all the sports in history. And while the human body is able to improve continually, its abilities to go further pale in comparison to those of machines. The technological advance is incomparably faster and the hunt for better performance and more speed is what drives the motorsport forward. Probably the biggest leap in history of performance in motoring was brought by force induction, especially turbocharging. And while the turbocharger may, in its appearance, remind the snail, it gave both racing and street vehicles an unprecedented dose of speed and performance. The life is full of paradoxes.
Turbocharger, or turbo, is now quite common part in both racing and street engines. The history of turbocharging begun in 19th century, but the road to perfection was long, bumpy and full of dead ends. The turbocharger is an extremely complex part, difficult not only to manufacture with precision, but also sensitive to quality of materials, performance tuning and also the oil used. However, the allure of massive increase in performance with relatively light and small device was huge.
Any advanced technology usually comes to ordinary life from racing or military development, and turbocharging is the latter case. However was its principle first described in late 19th century and patented by Swiss engineer Alfredo Büchi in 1905, the first mass application came with rapid development of technology in the World War II, when engineers first managed to deal with extreme temperatures. Turbochargers were uses on bombers like B-17 Flying Fortress, B-24 Liberator or iconic twin-fuselage P-38 Lightining fighter plane. And it was also in USA where the turbocharger first appeared in production cars, in 1962. But that was long before its real glory and ubiquity came…
The general principle of turbocharging is to get more air into the combustion chamber, compared to naturally aspirated engine. That, of course, means also more fuel and better ratio of power to displacement. The further enhance the efficiency, the compressed air is cooled on the way to cylinders, because the cooler the fuel/air mixture is when ignited, the more efficient the whole process is. The same basic principle is used with the other common way of forced induction – the supercharger. However, the supercharger is driven from the engine’s crankshaft, robbing the engine of part of its power. Turbocharger uses the residual kinetic energy of the exhaust gasses, which mean its work is “free”. In the real world, a good turbocharger achieves an efficiency of approximately 55 %, which is a real nice figure for a mechanical device.
Every turbocharger is comprised of the turbine (usually made of light alloy) and compressor (usually cast iron) part, with both turbine and impeller (inside the compressor housing) connected with a shaft on friction bearings (hence the sensitiveness on oil quality). The exhaust gasses drive the turbine part, while the compressor part, as its name suggests, compresses the air into the cylinders. So all that’s needed now is to add sufficient fuel, ignite and the powerful engine is born? Well, not really.
The turbocharger works with extreme temperatures, which reach up to 900°C in its core (for petrol engines). And while the common car engine operates usually at no more than 6.000 rpm, the turbocharger usually rotates several orders of magnitude quicker ( 100 – 150.000 rpm). This places extreme demands on balancing of the rotating parts, as well as precision of manufacture, temperature stability and durability of both turbine, compressor and both housings. Besides many advantages, the turbocharger also comes with one fundamental drawback, coming from the need to use the energy of exhaust gasses. When there’s not enough of them, the turbocharger has nowhere to reach for energy – which means it needs higher rpms and higher flow of exhaust gasses. And the bigger the turbo is (able to compress more air and fuel into the cylinders, thus achieving better performance), the more exhaust gasses it needs to work. This is the cause of so-called “turbo-lag”, when the engine lacks power before the turbocharger spools up and then suddenly bursts into power. To fine-tune the right size of the turbocharger and right pressure with the engine is really an uneasy task. Especially when more options come in the picture, like multi-stage turbocharging with multiple turbos, turbochargers with variable geometry of vanes (VGT, like the ones used in ŠKODA 2.0 TDI engines in 110 and 140 kW versions) and many other technical features. But as we said before, we got to the current stage of useability and performance of both street and racing technology through long development.
Engineers first managed to really harmonize the turbochargers with engines in the late 1960s. And of course, it was in motorsport. The biggest boom of turbocharging came in 1980s, when disclaimer “motorsport is dangerous” was on every ticket to F1 Grand Prix, when the fascination with turbo performance knew no bounds and the horsepower ratings reached absurd heights. Even the slowest formula cars had 1 000 hp and some teams were able to get up to 1 350 hp from their engines, with the pressure of 5.5 bar. By the way, this way when maximum allowed displacement was 1.5 litres. Then, FIA first reduced the allowed turbocharger pressure to 2.5 bar and then, by the end of 1980s, banned turbocharging altogether. Before it happened, F1s often achieved more than 650 horsepower from 2.5 litres of displacement, with maximum rpm of over 12.000. The safety of the was disputable at best.
And it was similar story with rally, when it soon turned out that the turbocharger is a good servant, but a bad master. It happened basically right after cars with the two greatest hits of the 1980s – the 4×4 and turbos – came into the picture. The turbomania came into its height in 1982, with advent of Group B. While it still had many rules and regulations, many teams took more like recommendations. Cars weighing much under a tonne often came with more than 450 horsepower from massively blown engines, displacing around 1.8 litres (those were official figures, unofficially, it was usually closer to 600). While the rules required some kinship with street vehicles, in reality, only the body lines were similar. The requirements to produce homologation series of street cars were also often circumvented. The rally was at the height of its hubris, and it was destined to fall. It didn’t take long. After a series of tragic accidents, the Group B was banned in 1986. It was not only the safety, but also the development costs of unique and highly specialized technology – closer to NASA labs than street cars – that made the WRC into a stomping ground for just a handful of richest teams, before ultimately killing it.
Turbo-boom in motorsport made its mark on the development of “civilian” cars as well. The turbomania of the 1980s brought first practical turbo engines, usually with low-pressure turbochargers. The turbo was now cool. The word “turbo” was everywhere on cars. Every car with forced induction boasted a prominent badge (and if possible, a fashionable “turbolook” bodykit). And it didn’t stop with cars. Turbo was on everything from T-shirts to beverages and toothbrushes. In Czechoslovakia, there was even a pop-rock band called Turbo!. It didn’t matter that in the centrally planned economy, turbochargers were limited to tractors and trucks. First Czech mass-produced car came much later, in the form of the first generation of ŠKODA OCTAVIA in 1996.
It’s more than 30 years since the end of Group B and craziest times in F1. During that time, the humankind learned to use turbocharged effectively. And not only with turbochargers – also with its ego and technological hubris. Today’s turbochargers in passenger cars are not there to maximize the performance at any cost. They still bring more power and allow small and frugal engines to achieve performance formerly limited to larger power plants, but they are optimized for the best power and torque curves, and especially to minimize the fuel consumption. And they are not reserved for the fastest models anymore. ŠKODA now offers turbocharged engines in almost the whole model range. From compact FABIA (1.0 TSI, 70 kW or more) to sportiest OCTAVIA RS 245 with two-litre TSI and 180 kW, or SUPERB limousine with up to 206 kW / 280 hp.
Even motorsport now cares much more about being safe, while staying attractive for the spectators, drivers and teams themselves. The rules are in place to prevent it from becoming a surreal technology festival for a few of the richest. For example, the turbocharger pressure is now limited to 1.5 bar and engines of rally cars have to be based on stock powerplants. As a part of technology sharing in VW Group, the new ŠKODA FABIA R5 now uses turbocharger from the sporty Audi S3. New rules make rally attractive for fans and more attainable for not only factory teams, but also privateers. And it works! Soon, there will be more than 200 customer FABIA R5s sold. And we don’t have to doubt that the modern rally is fun for spectators and drivers alike. Honza Kopecký and Ole Christian Veiby certainly don’t look bored in their rally cars!