Turbocharged Direct Injection
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Turbocharged Direct Injection (TDI) is the technology used for modern diesel engines produced by Volkswagen Group, and is widely used in passenger cars produced by the company (especially those sold in Europe).
Overview
The engine uses direct injection where a fuel injector squirts directly into the engine cylinder rather than the pre-combustion chamber prevalent in older diesels which used indirect injection. The engine is coupled with a turbocharger and intercooler to increase the amount of air that can get into the engine cylinders, thereby increasing the amount of fuel that can be injected and combusted. In combination, these allow for greater engine performance while also decreasing harmful emissions.Other companies also use similar technology today, but "TDI" usually refers to the engines used in cars made by Volkswagen, Audi, and related brands. Normally-aspirated engines (those without a turbocharger) made by Volkswagen Group use the label "Saugdiesel Direct Injection" (SDI).
The reduced material volume of the direct injection diesel engine reduces heat losses and thereby increases engine efficiency, at the expense of increased combustion noise. A direct injection engine is also easier to start when cold, due to the reduced heat loss of the design.
History
The first TDI engine was a 2.5L inline five-cylinder introduced in the Audi 100 in 1989. Over time, the TDI arrangement has been enhanced by improving the efficacy of the turbocharger, increasing the pressure at which fuel can be injected, and more precisely timing when the injection of fuel takes place. There have been a few major generations, starting with what are known as "VE" engines. In 2000, the Pumpe Düse (PD, variously translated "pump nozzle", "unit injectior", "pump injector") engine began to appear in Europe, eventually coming to North America a few years later.The PD design was a reaction to the development of common rail fuel injection by competitors; an attempt by Volkswagen to create an in-house technology of comparable performance that would not require any royalties to be paid. However, while Pumpe Düse engines had a significantly higher injection pressure than older engines, they couldn't keep up with common rail and weren't able to control injection timing as precisely (a major factor in improving emissions). PD technology was abandoned, and new engines appearing as of 2006 are using the common rail technique with piezo injectors.
A racing version of the common rail TDI engine made an impact in 2006 when it was used in the Audi R10, which won the 12 Hours of Sebring and 24 Hours of Le Mans, becoming the first diesel-powered car to win either of those races. Fuel economy was a significant factor, as the car didn't have to refuel as often as others in the race. The car used a special synthetic diesel blend as fuel.
Fuel
TDI engines, particularly newer ones with higher injection pressures, are less forgiving about poor-quality fuel than their 1980s ancestors. No. 2 diesel fuel is recommended since it has a higher cetane number than No. 1 fuel and has lower viscosity (better ability to flow) than heavier fuel oils. While some enthusiasts have run their cars on straight vegetable oil (SVO) or waste vegetable oil (WVO), both are discouraged for new engines, especially since the viscosity is much worse than regular diesel. Biodiesel can also be used if it conforms to specifications, though Volkswagen does not endorse its use in high percentages.See also
- List of Volkswagen TDI engines
- Turbodiesel
External links
- [TDI Club]
- [Turbo Direct Injection FAQ]
- [TDIClub Wiki]
- [General Biodiesel information]
- [Turbo Direct Injection or TDI for short]
- [Greater Cincinnati TDI Club]
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