What does TDI mean?
You have seen the advertisements for the Passat TDI and the Jetta TDI, and you may ask yourself, “what does TDI mean?” The short answer is: Turbocharged Direct Injection, but what is that and what does it do?
Diesel engines became popular in the 1970’s when gas was at a premium and consumers sought an alternative. But, the diesel engines of the time were described as loud, lumbering, and dirty. Often times, motorists would find their cars covered in black soot from driving a diesel. Diesel engines also presented problems starting in cold weather and problems with quick acceleration.
Today, the diesel engine has made great strides to, not only survive, but thrive in the hybrid era. The industry as a whole has worked to virtually eliminate the key pollutants associated with on-road diesel engines. According to a report from the Diesel Technology Forum, “Particulate matter emissions of new on-highway diesel engines have been reduced 83% since 1988. Emissions of nitrogen oxides have been reduced by 63% during the same time period. This has been accomplished largely through improvements in fuel delivery, the design of combustion chambers, and turbocharging.”
According to the website How Stuff Works, “Direct injection devices are now controlled by advanced computers that monitor fuel combustion, increasing efficiency and reducing emissions. Better-refined diesel fuels such as ultra low sulfur diesel (ULSD) will lower the amount of harmful emissions and upgrading engines to make them compatible with cleaner fuel is becoming a simpler process. Other technologies such as CRT particulate filters and catalytic converters burn soot and reduce particulate matter, carbon monoxide and hydrocarbons by as much as 90 percent.”
Volkswagen’s Turbocharged Direct Injection combines increased power with increased fuel economy.
How?
Volkswagen’s technology page explains it this way: “Fuel needs oxygen to burn and the engine has to be supplied with huge quantities of air to get enough. You can solve this problem with a bigger engine - or you can solve it with a turbocharger - as in the TDI. Driven by the exhaust gases, it squeezes air more tightly into the cylinders.”
“After being drawn through the turbocharger the air is then cooled by passing it through an air to air intercooler (cool air takes up less space than hot air), before entering the combustion chamber where diesel is injected directly into the cylinders at very high pressure through a nozzle. It's this intensive mixing of highly atomised fuel with the cooled compressed air that leads to better, more efficient combustion.”
"The pressure at which the diesel is injected into the cylinder is the key factor in diesel direct injection. The fuel has to mix swiftly with the compressed air in the cylinder. The higher the pressure, the more finely the diesel is atomised for an intensive mixing of the fuel and air particles. This, in turn, leads to better and more efficient fuel burning. The energy from the fuel is used more effectively and emissions are reduced."
The translation on the road is that Volkswagen’s TDI engines provide better fuel economy, less time spent at the gas pump, and lower overall maintenance costs as well.
