As part of the Sustainable Zoom-Zoom plan, Mazda is developing advanced powertrains that provide outstanding power alongside excellent fuel economy and emissions control.

We are planning to have a completely new powertrain line-up in place for 2010 and beyond, which will be sequentially introduced in all models. At the 2007 Tokyo Motor Show, we are exhibiting some of our latest technologies at the service of this aim.

Next Generation I-4 Direct Injection Gasoline Engine

Mazda’s DISI* engines balance sporty driving with outstanding environment performance. With the next generation engine in the series, we are aiming for a 15% ~ 20% improvement in dynamic performance and a 20% increase in fuel economy (compared with a Mazda 2.0L gasoline engine). Based on the direct injection system, we aim to reduce all energy losses (see figure on the right) and improve thermal efficiency through innovative engineering in a variety of technological areas. Among these technologies we are paying particular attention to direct injection, combustion control, variable valve system technology and catalyst technology. Also, among the various fuels on the market, we are studying the use of flex-fuel. 

*DISI:Direct Injection Spark Ignition

Direct injection technology

Cooling the intake air temperature is an excellent method of suppressing abnormal combustion such as pre-ignition and knock that might be caused by a higher compression ratio. Cooling the intake air temperature also contributes to improved power output by increasing air density. Fuel atomization and in-cylinder flow are important factors in improving air cooling. For the next-generation of swirl injectors, as used in the current MZR2.3L DISI TURBO and MZR2.0L DISI engines, we are researching technology to improve atomization and promote mixing through enhanced in-cylinder gas flow in order to increase the cooling effect. We are also looking for ideal combustion in a variety of driving situations by controlling the number and timing of direct injections, and also turbulence.

Combustion control technology

The combustion chamber shape is an essential factor in avoiding the unwanted influences of a high compression ratio. Mazda engineers employ advanced visualization and CAE technologies to study combustion chamber shapes capable of performing under higher compression ratios.

Variable valve timing technology

The conventional gasoline engine suffers from considerable pumping loss when driving around town and in other low-speed situations. To reduce this loss Mazda is currently advancing S-VT (Sequential-Valve Timing). We are investigating dual S-VT with a phase-variable mechanism for both the intake and exhaust sides, as well as a continuously variable lift mechanism now in development. If we can adjust the intake volume solely with a variable valve mechanism, it will be possible to reduce pumping loss and improve fuel economy. At the same time, we can also achieve the brisker response that is essential for exciting driving.

Catalyst technology

To meet the severe exhaust emissions regulations of the future, Mazda has developed a new catalyst employing single nano technology*. This includes a new and original catalyst structure, consisting of precious metal embedded in a catalyst support matrix. The new catalyst has the following key features: (1)Suppression of thermal degradation caused by precious metal aggregation, (2)Substantial improvement in the oxygen absorption and emission performance required for purification of the exhaust gases. As a result, this structure ensures that there is virtually no loss of purification efficiency, even under extreme conditions of use. We have also confirmed that the volume of precious metal required is reduced by 70% ~ 90% (Mazda’s in-company comparison) while maintaining existing purification efficiency. This is called single nano technology. Use of these technologies with a platinum or rhodium catalyst in a 3-way catalytic converter dramatically reduces the volume of precious metal required to purify emission gases.

*Single nano technology: Technology to control material structures at sizes smaller than conventional nano technology.

Next Generation Clean Diesel Engine

Excellent fuel-economy and substantial torque are characteristics that have made the diesel engine popular, particularly for long-distance travel in Europe. The diesel engine has also been the subject of clean technology development in response to strengthened European emission requirements, and has consequently become of interest because of its substantially low CO2 exhaust volume. We are pursuing the kind of fun-to-drive performance that conventional diesel engines cannot offer to allow stress-free driving up to high engine speeds. This is based on common-rail direct injection diesel turbo technologies which have been highly evaluated in Europe. To meet global requirements, we also aim to improve emissions and fuel economy by as much as ten percent. The following illustration shows the main technologies to fulfil our aims.

Direct Injection technology

This newly-developed technology is comprised of a high fuel pressure common rail system that controls piezo injectors.

The piezo element in an injector expands in nanoseconds (one billionth of a second) in response to a change in signal voltage, which results in far quicker response than the conventional solenoid injector using electromagnetic force for up/down movement. The piezo injector delivers a shorter injection time alongside dramatically improved fuel atomization and injection volume precision.  Our aim is to realize homogeneous mixing for waste-free combustion, at the same time improving power, fuel economy and emissions control.

Lightweighting

Compared with its gasoline counterpart, the diesel engine’s reciprocating and rotating components (pistons, connecting rods, crankshaft, etc.) are heavier, which creates the problem of a low rpm limit. With Mazda’s next generation 2.0L diesel engine, in addition to using an aluminum block, we thoroughly reduced the size and weight of reciprocating and rotating parts with the aim of achieving a similar weight to the gasoline version. As a result, we have not only realized smooth, high-revving performance, but also simultaneously achieved better fuel economy and lower NVH by reducing mechanical resistance.

Turbo system

A 2-stage turbocharger is used to yield optimally high turbo-pressure over a broader engine rev range than on the previous diesel engine, with the aim of obtaining a broad, flat torque curve. The turbocharger boosts torque at low rpm as well as acceleration response, delivering another advance in Mazda’s trademark driving pleasure. Further, by simultaneously increasing intake volume and EGR (Exhaust Gas Recirculation) volume at all engine speeds, from urban driving to highway situations, the 2-stage turbo delivers emissions performance that meets global requirements, and improved fuel economy through lean combustion.

Catalyst technology

･High-efficiency PM combustion catalyst

The oxidation catalyst in a conventional catalyst-supported diesel particulate filter (DPF) promotes combustion with carbon (the main constituent of particulate matter) using only the oxygen atoms on the surface of the oxide layer. By contrast, with Mazda’s new PM combustion catalyst, the oxygen atoms within the entire oxide layer are effectively used, thereby substantially accelerating carbon burning. This also shortens the time needed for the DPF to regenerate, enabling lower emissions and better fuel economy. In addition, on account of the new material’s high durability and minimal drop-off in performance, it is possible to use smaller volumes of the expensive precious metal.

Catalyst system

Since diesel engine exhaust gas contains a large volume of oxygen, it is a major challenge to reduce NOx (oxides of nitrogen that are a cause of acid rain) to N2 (nitrogen gas). In addition to an after-treatment system to purify the unburned exhaust gas components, Mazda is developing technology for its diesel engines that enables catalytic treatment of NOx in exhaust gases. We are developing a selective reduction system that adds aqueous urea to exhaust, and a NOx storage system for exhaust gas purification. These systems are being readied for future global deployment.

Next Generation RENESIS (Rotary Engine 16X)

Mazda is celebrating 40 years of rotary engine development since the introduction of the rotary engine Cosmo Sport in 1967. To mark the occasion, we have begun development of the direct injection 16X, a 1600 cc (800 cc x 2) powerplant with a new trochoid chamber shape aimed at further improving thermal efficiency and boosting torque at all engine speeds. The 16X is made possible through the experience and technology gained with RENESIS, a unit featuring side exhaust ports and other features that greatly advanced the rotary engine.

All-round change of dimensions

With the next-generation RENESIS, Mazda has changed the cocoon shape of the trochoid rotor housing. This marks a further evolution of the basic structure of the engine which began with an early period of over seven years spent researching the optimum trochoid shape, from the introduction of the first 10A (491cc x 2) in 1967, followed by the 13A (655cc x 2), 12A (573cc x 2) and the current 13B (654cc x 2). This shape change is brought about by reducing the rotor housing width and housing thickness while increasing the trochoid outline, resulting in a displacement increase to 800 cc x 2. But despite this dimensional increase, we were able to keep the engine itself essentially as compact and lightweight as the current RENESIS.

As for its specific shape, increasing the trochoid radius and eccentricity and reducing rotor housing width achieved a longer stroke, thereby shrinking the combustion chamber aspect ratio. Due to this modification, the surface area-to-volume ratio of the combustion chamber decreases, enabling a reduction in cooling losses. Also, since the very tight space in the combustion chamber is reduced, flame growth is promoted and the engine exhibits faster combustion and better fuel economy. As well as improving fuel economy-an essential part of environmental performance-we are simultaneously pursuing higher torque at all engine speeds.

Direct injection technology

The next-generation RENESIS is the first gasoline rotary engine developed to use direct fuel injection. The system inherits the basic design concept of the hydrogen rotary engine, injecting gasoline in a high-pressure spray during the intake cycle, promoting atomization and vaporization of fuel and the formation of a stable air-fuel mixture. The latent heat of fuel vaporization lowers the temperature of the air-fuel mixture, thus raising the engine’s charging efficiency. At the same time, it reduces fuel adhesion to the chamber wall, which has been a problem of the conventional port injection system, while promoting a more homogenous air-fuel mixture. This in turn leads to substantially improved thermal efficiency and increased torque, and Mazda is actively researching further improvements in efficiency.

Aluminum side housing

In developing the new engine, Mazda engineers have dramatically improved both power output and environmental efficiency. They have also contributed to further increases in fuel-economy and driving performance by lightening the vehicle weight. By keeping the engine’s exterior dimensions about the same as the current RENESIS, which allows more of the vehicle’s volume to be devoted to passenger space, and by using an aluminum side housing aiming at lighter weight than the current RENESIS along with various other measures, Mazda continues to advance the merits of the compact and lightweight rotary engine.

SISS (Smart Idle Stop System)

Drivers often let the engine idle at traffic lights or, particularly in urban areas, when stopped in traffic jams. Cutting the engine to stop the idling in these situations reduces fuel consumption by about 10% in Japan's 10-15 mode tests. The idle stop system saves fuel by automatically shutting down the engine when the driver brings the vehicle to a halt and automatically restarting the engine when the driver subsequently wishes to pull away. A conventional idle stop system uses an electric motor to restart the engine. However, Mazda’s SISS injects fuel directly into the engine’s cylinders while the engine is stationary and ignites the fuel to create downward piston force that serves to start the engine. This system not only saves fuel, but also restarts the engine more quickly and quietly than a conventional idle-stop system.

Piston stop position control

For the engine to be startable through the aforementioned operation, it’s vital for the compression-stroke piston and expansion-stroke piston to be stopped in positions that create the right balance of air volumes. Consequently, SISS effects precise control over the piston positions during engine shutdown.

Combustion restart technology

During automatic restart, the cylinders for combustion are indexed and fired from the stored piston positions at the time of engine shutdown. Even at extremely low rpm, cylinders are continuously selected for ignition, and the engine quickly picks up to idle speed.