01-03-2005
“Products like the Avensis express what we understand to be superior quality”, says Johannes Thammer, Toyota Europe’s Vice-President for Product Planning & Research.
The Avensis has been a hugely successful car for Toyota in Europe. Now two new 2.2-litre D-4D diesel engines join the group to make it one of the most comprehensive product ranges found in the D segment: 3 diesel (2.0, 2.2 – 177 DIN hp and 2.2 – 150 DIN hp) and 4 petrol units (1.6, 1.8, 2.0 and 2.4). At the time of its launch, the Avensis also became the first car in the world with a complete range of engines fully complying with EURO IV standards.
The 177 DIN hp 2.2-litre D-4D inaugurates Toyota’s revolutionary new concept for diesel engines - Clean Power - now possible through the adoption of the most innovative diesel technologies in the world, some of them unique to Toyota. Thanks to the carmaker’s world-beating Toyota D-CAT (Diesel Clean Advanced Technology), this 2.2 D-4D Clean Power has the smallest combined NOX and PM emissions among all diesel engines on the market. However, the unit boasts segment-beating levels of power and torque (177 DIN hp and 400 Nm between 2,000 and 2,600 rpm), combined with the lowest Noise, Vibration and Harshness (NVH) and, on average, 20% lower fuel consumption among engines of equivalent power (combined target fuel consumption of 6.1 l/100 km for Avensis Sedan).
The breathtaking 177 DIN hp 2.2-litre D-4D Clean Power engine is joined by a second 2.2-litre 150 DIN hp diesel engine, that adopts a second-generation common-rail system and a different turbocharger. Additionally, the Toyota D-CAT technology is exclusive to the most powerful version of the 2.2 D-4D engines.
Performance curves of the Avensis diesel engine line-up
With the addition of these new engines, the Avensis receives other important upgrades, including a new exterior colour (Storm Grey) and a new gearlever design (specific to the new 2.2 D-4D units).
Both 2.2 D-4D engines will be produced at Toyota Motor Industries Poland (TMIP), the latest Toyota factory built on the continent. The result of a €200 million investment by Toyota, TMIP boasts a production capacity of 150,000 engines per year, with a planned workforce of around 500 people.
With their promise of high power, coupled with low fuel consumption and cleaner technology, Toyota is confident that the new engines will contribute to a quarter of Avensis sales in 2005. With these two new engines, Toyota will be covering 95% of the needs of the D segment diesel market.
Lightweight and efficient
The 2.2-litre D-4D Clean Power engine is lighter than most engines in the 1.9 - 2.2 category, thanks to its all-aluminium construction - still a rare feature among diesel engines in the segment. Clever engineering, such as integrating the water and oil pump on the chain cover that has led to a reduction in weight of the oil pump by 5%, and its volume by 20%, has made the new engine 11% lighter than the current 2.0-litre D-4D that is available on the Avensis.
Noise and vibration have, again, been kept low by some ingenious engineering skills, such as the adoption of a balancer shaft that substantially reduces booming noise by up to 10 dB at higher revs.
At 15.8:1, the engine also boasts the world’s lowest compression ratio among production diesel engines. The effort the piston has to make to compress the air-fuel mixture is smaller, with a lower compression ratio. This has been made possible by the use of an advanced common-rail injection system and improved ceramic glow plugs that can achieve much higher temperatures (1175 °C, 100 °C higher than before) for more efficient cold-starting. Altogether, this not only means a quieter combustion, but also less heat build-up in the piston bowl for a more efficient burn and, in turn, better fuel economy and less emissions.
The material used for the cylinder liner is identical to the one used in the Toyota 1.4-litre D-4D engine, where it already boasts superior wear-resistance and a good adhesion to aluminium.
2.2 D-4D Clean Power engine
The majority of current common-rail systems employ solenoid injectors, which are actuated by a magnetic field generated by an electric current. The new 2.2 D-4D Clean Power engine, on the other hand, uses piezoelectric technology for the first time in this displacement class. The principle behind this is the capacity of certain materials to deform upon the application of an electrical charge, and return to their original state when the current is removed. The same concept is used on this engine, where each injector is composed of a stack of piezoelectric ceramic elements. When an electric current is applied to the stack, the elements expand instantly, allowing the fuel from the common-rail to be injected into the cylinder. Thus, larger volumes of fuel can be injected in a shorter time than is possible with conventional injectors. This in turn leads to greater fuel atomisation and more precise injection timing.
The new injection system has many advantages. For instance, Toyota’s new piezoelectric injectors are 10 times quicker than solenoids when producing an injection, and can perform up to 5 injections per cycle with single pilot injection at hot idle, and multiple injection at partial load. With piezoelectric technology, pilot injection timing can be optimised, leading to a handsome reduction in combustion noise.
Piezoelectric injector
Toyota’s piezoelectric common-rail system produces the highest injection pressure (1800 bar) and the highest number of injections per cycle (5 in total) among systems of this type. In addition, by adopting a piezoelectric system in cars like the Avensis (and in other models later on), Toyota becomes the first to bring this key diesel technology to the mainstream car market.
The 2.2 D-4D Clean Power engine uses a Variable Nozzle Turbocharger (VNT) that is electrically activated. VNTs have vanes installed in the turbine house that change position according to the speed of the exhaust gas flow. Although normally activated by a step motor, in this case the vanes are directly triggered by a direct-current electric motor. This allows the engine’s ECU to perform a more precise and progressive activation of the vanes, which helps increase the efficiency of the turbocharger. Additionally, the vane activation can be done at lower engine speeds, if necessary. Compared with the 2.0-litre D-4D, the turbine wheel inertia has been lowered by 30% by reducing the number of blades and their thickness. This contributes to a much quicker response at low speeds.
World-beating emission control system
The new 2.2 D-4D Clean Power is equipped with the revolutionary Toyota D-CAT. Additionally, the ultra-clean diesel technology allows the high-performance diesel to be the cleanest in the world in terms of combined NOX and PM emissions.
D-CAT features a Diesel Particulate NOX Reduction (DPNR) 4-way catalyst, which is the only one in the world that reduces NOX and PM simultaneously via a combination of a NOX-reduction catalyst with a particulate filter. The effective operation of the DPNR relies on the engine management system varying the air-fuel ratio in the exhaust gases.
To do this, a fifth injector, or Exhaust Port Injector (EPI), has been added and placed on the exhaust port. At the critical moment, fuel is injected into the exhaust gas flow in order to create the right stoichiometric conditions for the DPNR catalyst. This allows the DPNR catalyst to reduce harmful emissions.
Toyota D-CAT components
The 2.2 D-4D Clean Power comes coupled with a new 6-speed manual transmission that boasts smooth, quick and precise gear-change. This has been made possible by the use of a multi-cone synchroniser from first to fourth gears, which requires less force when shifting gears. It uses a slide ball bearing in the select lever shaft and fork shaft (high shift efficiency), as well as a shift-guide plate to decrease the amount of free play after shift. The re-shaped mass damper also improves shift smoothness.
It is robust in construction, as well as exceptionally compact at a mere 384 mm in length, beating other 6-speed transmissions of identical or even inferior torque capacity. The use of a 3-axis construction allows a reduction of 20% in length compared to a 2-axis configuration.
The lowest viscosity oil available today, for manual transmissions, has been used to contribute to fuel consumption reduction by 1%. Adoption of an oil-separator reduces losses, due to the oil agitation. And, last but not least, the transmission offers a wider gear-range (over 7.0:1).
The Toyota Avensis wants to be recognised as the cheapest car to run in the segment, proposing a captivating offer to fleet buyers.
The Avensis 2.0 D-4D currently holds the best insurance classification in UK (7), thanks to repair costs more than 20% inferior to the segment’s average after a 15 km/h impact test.
The new 2.2-litre D-4D is not only class-leading in performance and emissions, but also intends to innovate in terms of cost of ownership and durability. The adoption of an Oil Maintenance Monitoring System (OMMS) allows the extension of oil change intervals from 15,000 km up to 30,000 km, in comparison with the current 2.0 D-4D.
The 2.2-litre D-4D engine equals the 2.0 D-4D in terms of cumulative maintenance time after 100,000 km, which is also the lowest in the diesel D segment (4.2 hours). Moreover, this unit accepts mineral oil, which constitutes a cost advantage over other engines that only take synthetic or semi-synthetic oils.
In addition, an automatic belt adjuster and rush adjusters are adopted. This means there will be no need to periodically adjust belt tension or valve clearances throughout the engine’s lifespan.
The clutch is also self-adjusting, providing the right setup at any moment.
With the installation of the new 2.2-litre D-4D, the Avensis has received a new NVH package. This includes an acoustic windshield, thicker bonnet insulator, and additional sound-insulation components in the engine compartment. The level of thickness has also been increased on both floor and tunnel silencers. All this results in the Avensis 2.2 D-4D Clean Power being class-leading in terms of booming noise and vibration.
The front anti-roll bar’s spring rate has been increased by 20%, resulting in less body-roll. The front shock absorbers’ damping force has increased, allowing for a flatter ride, and the power-steering pump capacity has been intensified to allow for a quicker steering response.
Text and photos courtesy of Toyota Motor Europe S.A./N.V.
