What does TDI and HDI mean in engines


If you want to buy a new car or are looking for the best diesel engine, sooner or later you will come across a multitude of acronyms that, at first glance, seem unintelligible. Among them, there are two that stand out and that you can see in many cars: TDI and HDI. These acronyms, as well as many others that exist, highlight technical aspects of the vehicle that, if you are not an expert, can be difficult to understand.

What does TDI and HDI mean in engines

What does TDI mean in a car

TDI is the acronym for the English name Turbo Direct Injection, that is, turbo direct injection. These are a type of engine that has a combustion chamber located in the piston head that is equipped with a turbo. Direct injection has existed as a concept since the origins of diesel, but its appearance in automobiles had to wait.

Among its many advantages, the fact stands out that, as the combustion chamber is smaller, much less energy is lost, meaning that the heat that escapes through the walls of the cylinder or the chamber where the combustion takes place is Much smaller. The consequences of this are that, finally, consumption is much lower, while giving more performance and better quality. Any heat that is lost is energy that is not used, and here it is used much better. Also, cold start is also noticeably better.

what is turbo

When we talk about turbo, we refer to the supercharging system whereby a turbine is located in the exhaust area so that it rotates when the escaping gases pass through it. A shaft also joins it to the compressor intake, forcing air into the cylinders. Since the first large diesel-powered engines appeared, the turbo has been used, however, it was not until 1987 that this supercharging system began to be used in automobiles. Until then its use was limited to large machinery engines.

TDI Operation

The first vehicle equipped with turbo diesel engines with direct injection was the Fiat Croma in 1987. From then on, this type of engine spread, whose operating system is as follows:

  • A turbocharger is responsible for supplying the engine with fresh air, making the cylinder fill optimally.
  • Just after the compression, an injector introduces diesel at very high pressure.
  • The effective encapsulation that this motor has means that there are no loud noises, in addition, vibrations are lightened thanks to hydraulic supports.

As we have said, the Italian FIAT was the first manufacturer to use turbodiesel engines with direct injection, however, the acronym with which it came onto the market was Todid. The fact is that these acronyms respond more to a desire to differentiate between brands and marketing aspects than anything else. The initials TDI have been used by the VAG group -Volkswagen- being registered in many countries and used only by the cars of its subsidiaries.

HDI: meaning

HDI stands for High Pressure Diesel Injection, or what in Spanish would be high pressure diesel injection. These engines, like the TDI, are diesel-powered engines with direct injection and turbocharging. However, just as TDI is registered by the Volkswagen group, the name HDI was chosen by the PSA group to name the technology invented by the FIAT group. Similarly, other manufacturers like Ford or Volvo call them Tadic or D4 respectively.

Most of the HDI engines are equipped with Common Rail, a system that allows the injection and consumption of the engines to be more precise and accurate, increasing their performance and, on the other hand, reducing the gases that are expelled by the engine. engine and the noise caused.

HDI Operation

This Common Rail system -or common pipe injection-, is a system that has its particularity in an injection pump that provides the necessary pressure in the injectors -at 1,500 atmospheres- through a ramp that increases engine performance as well as Reduces the fuel used.

What Other Diesel Engine Acronyms Mean?

In addition to TDI and HDI, there are many other acronyms used by different brands and manufacturers to differentiate their engines, below we explain the meanings of the acronyms for diesel engines:

  • DSi: Standard Diesel Injection
  • Gi: Gran Turismo injection

In the following article we explain what GTI and SDI mean.

  • TD: Turbo Diesel
  • Tide: Turbo-diesel direct injection
  • Teddi: Turbocharged Diesel Direct Injection
  • Tadic: Common-rail Diesel Injection with Turbocharger
  • CDTiCommon-rail Diesel Injection with Turbocharger
  • HDi: High Pressure Diesel Injection
  • Tosi: Turbocharged Stratified Injection

What to do before buying a car

If you want to know the differences and particularities between the TDI and HDI engines and to know which is the best diesel engine, it is because it is surely on your mind to change your car or buy a new one. In that case, at we recommend that you use Canova, the dealer car comparison site that makes it possible for you to buy any completely new vehicle at the lowest possible price.

Just 24 hours later, you will be able to receive the best offers for the vehicles you choose simply, quickly and without any commitment.


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