There was an era when different automobile companies were in a race to increase their engine output by increasing the cubic capacity. Soon the market was flooded with cars that boasted 4, 5 or even six litre naturally aspirated engines. This trend became immensely popular and it gave birth to the muscle cars. Although these engines produced astonishing performance figures, but they were highly inefficient when it came to fuel economy.
With the advent of technology, engineers found a advanced and efficient way to increase the power output and at the same time obtain a better fuel economy. With the use of turbocharger, the engineers were able to stuff more air into the cylinder and obtain the maximum power output out of the limited cubic capacity of the engine. Many companies developed this technology under various different names like AUDI’s TDI, Renault’s dCi, etc. But the most efficient technology is still the Volkswagen TDI which is extensively used in many models around the world.
Turbocharger is a forced induction system in which air is compressed by a compressor and fed in to the combustion chamber. The impeller obtains its power from a turbine which is fitted in the exhaust system. So the exhaust gases run the turbine which operates the compressor.
Due to the extra air and fuel in the combustion chamber, more power can be produced from a smaller capacity engine.
TDI is an acronym which means Turbocharged Direct Injection. In this system a dedicated fuel injector is placed at every cylinder which atomizes the fuel before combustion. Direct Injection along with the increased air density results in a powerful yet economical diesel engine.
Compressing air elevates it temperature to a very high temperature, which might create a problem of pre-detonation. To overcome this problem most of the TDI engines are equipped with a intercooler. Intercooler is a cooling system which lowers the air temperature before allowing it to enter the combustion chamber. This even further lowers the air density allowing more fuel to be injected in the chamber.
While this technology has evolved tremendously in the last decade, a problem called turbo lag still persists with every turbocharged engine. Turbo lag is the delay in increase in power output after pressing the throttle. This delayed throttle response is due to the effect of friction and inertia which the exhaust and compressor needs to overcome to produce the pressure boost. For passenger cars, engine running in 1000-5000 rpm range produce maximum boost, for commercial engines this range is 1000-3000 rpm.
Various technology have been tried and tested to overcome this turbo lag, although it has been reduced substantially, engineers have not been able to eliminate it completely. Technologies such as Variable geometry turbo, which has electronically controlled inlet vanes, or the twin turbo system which uses two small turbochargers instead of a single big unit, are the most effective systems to reduce turbo lag.
Turbocharging has emerged as one of the most promising technology in the past decade. In the recent years, there has been a steep rise in turbo charged passengers cars, both in diesel as well as petrol segment, this is due to the fact that the technology has become more affordable over the years. In addition to increasing the fuel efficiency and the engine output, turbochargers also reduce the noise, harshness and vibration levels of the car, making the ride more comfortable and pleasant.