Mazda's 2.0-liter MZR PZEV petrol
Mazda's new MZR in-line four-cylinder petrol engine range powers Mazda's new generation cars, and is currently employed in the Mazda6, the Mazda2 and the latest model, the Mazda3. They provide typically-Mazda performance characteristics with linear acceleration feel and lively response to accelerator-pedal inputs with ample torque for powerful acceleration in a whole range of driving situations, including urban driving with light accelerator-pedal inputs.
Another major feature of the MZR engine series is its outstanding environmental performance, with all derivatives achieving a Euro Stage IV ranking. The entire MZR engine range, however, has been designed to meet even tougher emission standards on the horizon and the 2.0-liter PZEV engine will be so clean-running that it meets the PZEV regulations adopted by the Green States in the US. The PZEV standard is the world's strictest for exhaust gas emissions of petrol engine vehicles.
To meet the PZEV regulations a vehicle must satisfy all of the following three conditions:
1) Compliance with the Super Ultra-Low Emissions Vehicle (SULEV) standard
2) Compliance with the zero evaporative emissions standard
3) Provide a warranty to meet standards in 1) and 2) above for 150,000 miles or 15 years of service, whichever comes first.
The new Mazda 2.0-liter MZR PZEV derivative will comply with these stringent requirements in both the five-speed manual and four-speed automatic transmission versions, and will be sold beginning early in 2004 in five US Green States (California, New York, Massachusetts, Maine and Vermont).
In order to ensure SULEV compliance, the new engine includes advanced exhaust emission technologies, some of which are already employed in the base MZR engine and contribute to low emission performance of the new Mazda3. These technologies include:
Reversed Intake-Exhaust Layout
Mazda3's 2.0-liter MZR base engine features a reversed intake-exhaust configuration, with the intake system located at the front of the engine and the exhaust system at the rear. This shortens the distance between exhaust ports and the catalytic converter, allowing exhaust gas to retain its high temperature on delivery to the converter. This promotes faster activation of the catalyst for improved exhaust gas purification.
Tumble Swirl Control Valve (TSCV) and advanced EGR
A tumble swirl control valve (TSCV) and an advanced EGR system are current employed in the base MZR engine line up as well. Fitted in the intake manifold, TSCV optimises the intensity of tumble and swirl in the combustion chambers to promote a favourable fuel-air mixture for more stable combustion. The engine's advanced EGR system reintroduces some of the engine's exhaust gas into the combustion chamber to minimize pumping loss and improve fuel economy. At the same time, by increasing the volume of inert exhaust gas in the intake charge, EGR lowers the combustion temperature which helps reduce NOx emissions.
Reduction of friction loss
The base MZR engines also employ shape-modified, lightweight pistons and low-friction piston rings, and shimless tappets with a low frictional coefficient finish, all of which reduces friction and improves fuel economy for less CO2 emissions.
Mazda engineers incorporated several additional advanced components to the 2.0-liter MZR PZEV in order to ensure compliance to tough PZEV emission standards. These include a stainless steel exhaust manifold with double-skin construction for improved temperature retention of exhaust gas. This encourages higher-temperature exhaust gas delivery to the catalytic converter. The catalytic converter located immediately downstream from the exhaust manifold has a high-density carrier with a thin-walled structure (wall thickness: 2.5 mil) and 900 cells per square inch (dual beds), yielding vastly improved performance of the catalyst itself.
A linear O2 sensor installed in the exhaust manifold feeds data back to the engine control system about the concentration of residual oxygen in the exhaust gas. This data is used to continuously optimise the fuel-air ratio, to improve combustion efficiency and maximize exhaust gas purification by the catalytic converter. And finally, the Mazda 2.0-liter MZR PZEV engine employs 12-hole injectors to promote finer atomisation of fuel and improved overall combustion and emission performance.
The engine also contains advanced technology to meet zero evaporative emission standards. These include an intake HC trapper, which adsorbs hydrocarbons (HC) discharged from the combustion chambers via the intake manifold when the engine is switched off, thereby reducing the HC volume escaping into the atmosphere.
Engineers also made changes in, and multi-layered, the materials for tanks and pipes. For instance, steel is used for the fuel tank and fuel supply line to eliminate their penetration by evaporative emissions. Additionally, the evaporation pipe leading from the fuel tank to the canister, and the purge pipe from the canister to the engine, have a multi-layer nylon section, again to reduce permeation by HC. And to minimize vapour leakage from pipe joints, ring-shaped quick connectors are used with rubber sealing on the inside. The canister structure has been modified to a multi-layer type with a larger purge valve installed to reduce HC discharge.
<2.0-liter MZR PZEV>
Type Water-cooled, in-line 4-cylinder 16-valve DOHC petrol
Bore x Stroke 87.5 x 83.1
Maximum power 107 kW/146 PS at 6500 rpm (target)
Maximum torque 179 Nm at 4500 rpm (target)