Over the past few years the Mazda team has offered an engine technology that’s called SkyActiv. This technology is developed to deliver the full range of torque at a much lower rpm than you would have if you had a normal engine. When this technology first made its way to the market it was able to offer quicker acceleration without causing us to need to have turbocharging, but with the advancement of regulations that will make it necessary for us to have lower emissions, better fuel mileage, and more direct power, the use of forced induction isn’t all that’s caused Mazda to move to the SkyActiv-X technology.
HCCI – Sort Of
The ideal development of a gasoline engine would be to make it operate in a similar manner to a diesel engine. This is known as Homogenous Charge Compression Ignition, which allows the compression to take place without the need of a spark for the combustion. Because diesel models are more efficient and offer the low rpm torque delivery this is the desire offered. The expectation is to have lower emissions as well if this engine were developed and possible when being offered with the gasoline as the fuel.
In order to create the SkyActiv-X technology for the engine that will drive your vehicles in the future, Mazda came close to the HCCI development with this engine technology. Because gasoline is more volatile than diesel this type of engine wasn’t possible before computerized controls for the engine, but now that we have this quality, it is possible. The difference with this new engine technology is the lack of a need for a spark to create the combustion that takes place to power the vehicle and allow it to drive along the road. Right now, the Mazda team was able to get HCCI to work in their lab, but in only a very narrow range of engine speeds and power.
A Unique Solution
The SkyActiv-X technology doesn’t do away with the spark plugs entirely. Instead, this engine technology makes it possible to have the ignition take place by using fuel, air, previously burned exhaust gases, and a super-lean charge of fuel. This small charge of fuel is what’s ignited by the spark plug to help create the pressure wave that compresses the mixture. By using recirculated exhaust gases the emissions are lowered and the power levels are improved. This engine technology is called Spark Controlled Compression Ignition (SPCCI).
The SPCCI engine works well and at a broader range than the HCCI engine, but there are times when a conventional engine is needed. This happens at higher loads and higher engine speeds in which Mazda would have to alter the engine for pure spark ignition. Because the SPCCI engine has the spark system always operational, the only challenge is to switch to SI model with the fuel injection and spark timing need to be adjusted, which is an easy thing to do in this particular engine.
If Mazda were to change to purely HCCI engine technology, the high loads and higher engine speeds would be difficult to manage and cause a challenge because the spark plugs wouldn’t be present. By using the SPCCI system and making this the new SkyActiv-X system, we see this new engine technology will be perfect for the drive and be able to handle every scenario with simple computerized changes that can be programmed and made while you’re driving. The expectation is that with the new SkyActiv-X system we’ll have more powerful and more efficient engines across the Mazda lineup in the upcoming years.