The New Toyota Avensis 2.2 D-4D

Press Release

Engine construction

 

Lightweight and efficient

 

·     The 2.2 D-4D engines feature a lightweight, all-aluminium construction

·     Aluminium block is derived from Toyota’s AZ petrol engine family

·     Components, like water and oil pumps, are fully integrated, reducing their size and weight

·     177 hp 2.2 D-4D features the world’s lowest compression ratio – 15.8:1

·     This engine is also equipped with more efficient, latest-generation

·     ceramic glow plugs

 

Weight-saving measures

 

·     All-aluminium construction

·     Derived from a petrol engine block

 

Both 2.2 D-4D engines were developed to be light and compact in order to reduce fuel consumption and harmful emissions, while simultaneously having a lesser impact on the vehicle’s driving dynamics through more favourable front/rear weight distribution. In order to achieve this goal, the adoption of an all-aluminium construction was the natural choice. The development of the world’s first diesel entirely produced in aluminium, the 1.4-litre D-4D installed in the Yaris, has given Toyota considerable experience in replacing cast iron with aluminium as the material of choice for diesel engine blocks.

 

In 2001, Toyota took the aluminium engine block of the 1.5-litre petrol engine installed in the Yaris T Sport as a base for its 1.4-litre D-4D diesel. For the new 2.2 D-4D engines, Toyota has adopted the aluminium block of the AZ petrol engine family, to which the 2.0-litre and 2.4-litre units (both also available in the Avensis) belong. The cylinder bores use cast iron liners for greater resistance to wear.

As a further weight reduction measure, the oil cooler is also entirely produced in aluminium.

 

Integration is a key factor when you want to reduce weight in an engine, since you can adopt the same structure to fit several components at the same time. This is what the development team has done with the water and oil pumps. Traditionally separate components, the water and oil pump are fully integrated into the chain cover. Thanks to this, the oil pump is now 5% lighter and 20% more compact.

 

As a result, the two versions of the 2.2 D-4D engine – 150 DIN hp and 177 DIN hp – are lighter than other competitor engines that use a traditional cast-iron block.

 

In addition, new, 2-millimetre piston rings were adopted, featuring a lower tension. This allows a reduction in friction losses.

 

World’s lowest compression ratio

 

·     More efficiency

·     Lower NOX emissions

·     Reduced levels of noise and vibration

 

One of the key factors for the great efficiency and low NVH of the new 2.2 D-4D engines is their low compression ratio. At 15.8:1, the 177 DIN hp 2.2 D-4D engine boasts the world’s lowest compression ratio among production diesel engines. The 150 DIN hp version uses 16.8:1, a significantly low figure.

 

A lower compression ratio means the engine has to use less effort to compress the mixture, which means higher efficiency – more performance with lower fuel consumption.

 

Leaner engines (that adopt a high air/fuel mixture, the case with diesels) tend to produce high levels of NOX (nitrous oxides) because they cannot use a larger amount of fuel to reduce the heat build-up in the piston bowl. This leads to higher combustion temperatures. By reducing the compression ratio, it is also possible to decrease the combustion temperature with a positive impact on the generation of NOX.

 

Furthermore, by reducing the compression build-up inside the cylinder and combustion chamber, it is also possible to reduce the noise and vibration caused by each explosion. This solution also gave engineers the freedom to develop lighter moving parts and the lightweight aluminium block, with no negative influence on durability and reliability.

 

Such low compression ratios are only possible through the adoption of state-of-the-art diesel technologies in components such as the new-generation common-rail system and the glow plugs.

 

Ceramic glow plugs

 

·     More durability

·     Quicker cold start

·     No white smoke emission

 

The new 177 hp 2.2 D-4D diesel engine is equipped with newly developed ceramic glow plugs. The adoption of ceramic materials to produce glow plugs was pioneered by Toyota in 1982, with the introduction of the L and C diesel engine families. The first members of this engine series in Europe were the 2.4-litre for Hiace and Hilux and the 1.8-litre available in the Corolla since 1982. Today, most of the Toyota diesel range adopts this technology.

 

Few materials have greater heat resistance than ceramics and this is the reason why, for instance, they are adopted in the Space Shuttle to cover its underside and frontal section. The same principle drove Toyota engineers when they decided to choose this type of material – its ability to stand much higher temperatures allows the Toyota ceramic glow plug to maintain the same efficiency for much longer than conventional metallic glow plugs, a clear advantage in terms of durability.

 

Furthermore, the thermal conductivity of ceramics far exceeds that of metals. For this reason, ceramic glow plugs can reach the ideal temperature more quickly than metallic plugs and this translates into more rapid cold starts at lower air temperatures.

 

With more than 20 years of experience in developing ceramic glow plugs, Toyota has equipped the new 177 hp 2.2-litre D-4D engine with an evolution of this technology; now able to reach much higher temperatures – 100 °C more than the previous generation of ceramic plugs.

 

The new generation of ceramic glow plugs not only allows a quicker cold start, but also reduces the formation of white smoke. This is possible because the combustion chamber more rapidly reaches the ideal temperature.

 

Injection and induction systems

 

Power with efficiency

 

·     State-of-the-art piezoelectric injectors

·     Piezoelectric injectors are twice as fast as solenoid

·     Highest injection pressure among piezoelectric systems: 1800 bar

·     Up to 5 injections per cycle, with smaller time gap between injections (0.1 ms)

·     Electrically-activated turbocharger allows more precise control and higher low-end torque

·     Turbocharger’s turbine wheel inertia has been lowered by 30%

·     New intercooler features heat exchange area 8 times bigger than before

 

Sophisticated common-rail injection system

 

·     Piezoelectric injectors

·     Highest injection pressure

·     Up to 5 injections per cycle

 

The majority of current common-rail systems use solenoid injectors, which are actuated by a magnetic field generated by an electric current. The new 177 hp 2.2 D-4D engine, on the other hand, uses piezoelectric technology for the first time in this engine size. The principle behind it is the capability of certain materials to deform upon the application of an electrical charge, and return to their original state when the current is removed.

 

Each injector contains a stack of piezoelectric ceramic elements. When an electric charge is applied to the stack the elements expand instantly, lifting the injector’s nozzle needle, which allows the fuel from the common-rail, kept at a very high pressure, to be injected into the cylinder.

 

Piezoelectric injectors can inject larger volumes of fuel and are twice as fast as solenoid injectors, since the nozzle needle can open and close faster.

Each injector features 10 nozzles, four more than can be found in the solenoid injector of the 2.0 D-4D engine. Each nozzle has a diameter of 0.13 mm.

 

Toyota’s piezoelectric common-rail system produces the highest injection pressure among systems of this type – 1800 bar.

 

Thanks to these improvements, the fuel spray achieves superior dispersion and atomisation. As a result, it is possible to achieve combustion at a lower pressure.

 

Furthermore, the new piezoelectric common-rail system can perform up to five injections per cycle with single pilot injection at hot idle and full load, and multiple injections at light and mid load. With piezoelectric technology, pilot injection timing can be optimised, leading to a significant reduction in combustion noise. In addition, it is now possible to reduce the time between injections to 0.1 ms.

 

This state-of-the-art common-rail system is a central factor in achieving class-leading levels of power and torque, with high fuel efficiency. In addition, it sets Avensis at the top of the D segment in terms of low NVH.