SKYACTIV technology is a series of development by Mazda, which is developed to increase Engine efficiency and increase engine output. SKYACTIV technology was initially announced to be used in new engines, transmissions, body, and chassis, which appeared
SKYACTIV’s precursor, The Mazda SKY concept first featured a 2.3 litre Direct injection gasoline engine, a Mazda SKY-D 2.2 litre diesel engine, a SKY- Drive AT transmission, a Mazda Kiyora with Sky-G 1.3 engine and Sky-Drive AT, was unveiled at the Tokyo Motor Show in 2008.
The SKYACTIV-G was previously known as SKY-G are all direct injection engines, powered by gasoline. The speciality of this engine is that the compression ratio is increased to 14:1, which is stoichiometric air fuel ratio, means that it is the A/F ratio where the combustion is most efficient. However, this ratio can cause normal engines to produce engine knock due to high compression, exhaust gas is reduced via a-4-2-1 engine exhaust system, by using a piston cavity, and adjusting fuel injection, and also the combusting duration minimized by increasing air flow, injection pressure and multi-hole injectors.
SKYACTIV engines has an all-aluminum construction with chain driven DOHC, with variable valve timing and direct injection, it meets emission standards. SKYACTIV-G engines for the US market has a lower compression ratio of 13:1 allowing them to combust better on standard gasoline with as little as 3-5% reduction in torque and FC.
Mazda begins to rank thing up when it comes to Gen-2 SKYACTIV engines. Mazda uses HCCI(homogeneous charge compression ignition to increase the compression ratio up to 18:1, which is incredibly high. HCCI engines requires microprocessor and physical understanding of the ignition process to control it. HCCI engines compresses the mixed air fuel to a point of auto combustion, eliminating the need of use of spark plugs.Since HCCI engines are fuel-lean, they can operate at diesel like compression ratio(18:1) as mentioned earlier, thus achieving 30% higher efficiency than conventional spark ignited gasoline engines.HCCI also can operate on gasoline, diesel fuel and most alternative fuels such as E-85. It also avoids throttle losses, which further improves efficiency. This technology creates diesel engine like efficiency with gasoline engine emmisions. Even without a catalytic converter, HCCI engines can achieve a very low Nitrogen Oxide reading, although unburned hydrocarbon and carbon monoxide emmisions still require treatments to meet automotive emmisions regulations.
The SKYACTIV-D is a family of turbo diesel engine. Designed to comply with the global emission regulations. In order to eliminate the need of Nitrous Oxide and particulate treatment in comtemp diesel engines, compression ratio is further decreased to 14:1. Cold start is made possible by multi-hole piezo injectors with 3 programmable injection patterns, and adoption of ceramic glow plugs. Engine misfiring during cycle is prevented using variable valve timing at the exhaust valve, which opens it during intake stroke, which increases engine air temperature. Another interesting point about the SKYACTIV-D is that it also uses a two stage turbocharger, where one small and one large turbos are selectively operated according to driving conditions.
Apart grom the G SKYACTIV also have SKYACTIV-Drive, SKYACTIV-MT, SKYACTIV-Body, SKYACTIV-Hybrid, and also SKYACTIV-CNG, which is powered by compressed natural gas.