Mazda SkyActiv engine . Click image to enlarge
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By Jim Kerr; photos courtesy Mazda
Mazda’s SkyActiv technology
You will be hearing a lot about Mazda SkyActiv technology in the coming years. SkyActiv started with research back in 2007, and part of it is being introduced this year to Canada in the 2012 Mazda3. This is more than just one technology, and is the result of Mazda’s commitment that by 2015, it will improve fuel economy by 30 per cent worldwide over its 2008 models, without sacrificing the fun driving attributes Mazda vehicles are known for.
SkyActiv technology falls into three areas of the vehicle. The first is to develop new engines, which Mazda has done with new gas and diesel engines that feature 14:1 compression ratios to optimize engine efficiency. The second part is to develop highly efficient transmissions for effective transfer of power; the third part is to use technology to develop high-strength bodies and chassis that maximize safety and performance while reducing vehicle weight too.
Mazda SkyActiv automatic transmission. Click image to enlarge
Let’s look at the new SkyActiv engine technology. This technology is first being introduced in Japan in a 1.3-litre engine on the 2011 Demio, known here as the Mazda2; we will see it here first on the Mazda3. Details on the Mazda3 engine have not been released yet, but it will likely be a 2.0-litre direct-injected gasoline engine. The high 14:1 compression ratio is a world first for a production engine, and combined with the SkyActiv automatic transmission, Mazda claims highway fuel economy of just 4.9 litres per 100 km.
Most current gasoline engines operate with a compression ratio of between 9:1 and 11:1. If compression ratios go too high, there is too much cylinder pressure and the fuel begins to self-ignite, or detonate. We hear it as “pinging” or rattling. Inside the engine, the result is a series of rapid and severe vibrations that can quickly destroy piston rings, pistons, bearings and even crankshafts. Mazda has created an engine that will operate at 14:1 compression ratio without this destructive detonation.
Gasoline engines are convenient but not necessarily efficient. Only about 20 to 30 per cent of the energy in the fuel is used effectively. The rest is lost in powertrain and heat losses. Even a slight reduction in these losses pays off with substantial improvements in performance and fuel economy. By increasing the compression ratio to 14:1, more energy from the fuel is converted into cylinder pressure, which provides power to turn the crankshaft. The result is about 15 per cent better fuel economy, along with 15 per cent more torque.