What HDi is and how it works

Introduction

For many years the Peugeot diesel engine range has been regarded as one of the most reliable and efficient within the European car manufacturing market. Up until around 1999 the Peugeot 306 Dturbo was fitted with the reliable yet slightly noisy XUD9TE turbocharged diesel engine which produced a reasonable 92bhp. The XUD9TE was a mechanical engine, which meant it had no ecu control over injection timing and boost control, which was one cause for its noise.

Peugeot diesel engines changed considerably with the release of the Peugeot HDi diesel range which boasted better fuel economy, lower exhaust emissions and greatly reduced engine noise. The Peugeot HDi diesel engines use a number of technologies but the main difference in comparison to the mechanical turbo-diesel engine is the addition of an ecu to finely control fuel injection. The rest of this article describes the operation of the HDi engine, however it is not my own work so it is being provided for reference only.

I found this mainly on the Russian Peugeot website at www.peugeot.ru

1. High pressure Direct Injection
2. Breakthrough technology
3. Behind the wheel
4. A high-performance engine
5. Economy
6. Respect for the environment

High pressure Direct Injection

Peugeot has worked ceaselessly over the past decades to develop its reputation as the world's leading manufacturer of diesel engines. It comes as no surprise, therefore, that Peugeot should have used the latest Common Rail technology to create a high-pressure direct-injection motor known as the HDI.

HDI: Under this system, the fuel is injected under high pressure directly into the combustion chamber. The HDI badge, therefore, identifies both this new type of engine and those cars in the Peugeot diesel range that are equipped with the HDI system.

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Breakthrough technology

HDI technology depends on an essential component - the Common Rail system.

Electronically controlled injectors (A) are linked to the same fuel feed pipe (B), which is kept under very high pressure (1350 bars). A highly accurate onboard computer, which is specific to the Common Rail system, monitors a wide range of parameters including the engine temperature, the air temperature, the atmospheric pressure, and even the position of the accelerator pedal. Taking these factors into account, the computer is then able to regulate the various processes in the engine - the fuel supply, the injection pressure and the rate at which the fuel is injected into each cylinder.

The injectors have variable control heads which allow a very precise dose of diesel to be injected into each cylinder. The computer makes sure the fuel is injected at the optimum moment.

The quantities of fuel injected and the length of each fuel injection are regulated independently of the injection pressure and the engine turnover. This separation of functions allows:

• A pre-injection, or "pilot injection", of a limited size and duration. This helps reduce engine noise and the amount of pollutants emitted by the motor.
• A main injection that is regulated according to the size of combustion spark and power output required.

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Behind the wheel

In order to optimise the power output and acceleration, while at the same time maintaining fuel economy, the roller-and-pawl valve driving system has been designed to reduce engine friction. The pistons, drive-rods and engine valves are significantly lighter (by 50% in the case of the latter), resulting in much less inertia from the engine's moving parts.

Responsiveness at low revs

The Common Rail system maintains the fuel injection under high pressure even at low turnover. This allows the engine to develop high torque at low revs and across a wide power range. The result is an engine which is smooth, responsive and which offers excellent pick-up for safe and easy overtaking. In addition, fuel economy is maintained even at low revs.

A significant reduction in noise and vibrations

The pre-injection, or "pilot injection", helps warm the cylinder before the main fuel injection, thus reducing ignition time and the amount of fuel burnt up at the beginning of the combustion process. The immediate result is a significant reduction in the engine "rattle" so typical of diesel motors, and overall sound levels become similar to that of a petrol-driven motor.

Reduced engine friction, extra-light moving parts and the ribbed design of the engine casing help to greatly decrease the vibrations caused by the motor.

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A high-performance engine

The HDI engine's performance is the result of an advanced optimisation study which combines:

• A Common Rail high-pressure direct-injection system.
• A supercharged, geometrically aligned intake system.

The HDI motor has been designed to give high torque a low revs.

HDI engine specifications
Type of engine	DW 10 ATED transversely-mounted, four-cylinder, eight-valve
Capacity	1997 cc
Maximum power output	80kW (110 bhp) at 4,000 revs per minute
Maximum torque	250Nm at 1,750 revs per minute
Injection	Common Rail high-pressure electronic injection
Turbocharging	Turbocompressor and air exchanger
Power Distribution	Overhead camshaft and direct-drive fan belt

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Economy

The HDI motor offers a fuel saving of 20% compared to the previous generation of diesel engine. Service intervals are also further apart, every 20,000 km instead of every 15,000 km.

This exceptional economy is the result of three innovations

The Common Rail combustion system
Developed in conjunction with Bosch, the Common Rail combustion system uses a high-pressure pump (up to 1,350 bars). The amount of fuel supplied to the cylinders can be precisely controlled thanks to the onboard computer. The small bore of the injection holes guarantees the fuel is finely vaporised before combustion.

A specially designeed combustion chamber
The combustion chamber has been designed to optimise air dispersal (swirl), and ensure a highly consistent fuel-air mix. This contributes to an almost-total burn up of engine gases.

A new type of engine oil
The HDI engine uses a new type of oil which has been designed to highly economical.

The engine constructions features:

• A 12%-reduction in weight, achieved through the use of lighter components.
• A decrease in engine friction.
• Even greater reliability

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Respect for the environment

"The fuel burns more efficiently, which means it burns more cleanly."

HDI technology, and in particular the "pilot injection" feature, guarantees a more efficient combustion and a more complete burn up of the fuel. This results in a reduction of exhaust emissions at source.

This "chemical continuum", which integrates the combustion and de-pollution cycles, is the result of extensive studies, while Peugeot's in-depth knowledge of the composition of exhaust emissions has allowed it to develop the best post-treatment of emissions possible.

Thanks to a 20% reduction in greenhouse gasses (CO2), a 50% reduction in ozone-harmful emissions and a 50% reduction in soot particles compared to normal standards, the HDI engine emits hardly any exhaust fumes. The HDI motor thus helps to protect the environment.

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