Mazda unveiled its new SKYACTIV-X SPCII engine last week at the Tokyo Show 2017.
A new petrol engine may not seem all that earth shattering, especially given the fact that the UK wants to ban them by 2040.
However the new SKYACTIV- X engine could bridge a gap between petrol and electric vehicles in future.
The engine combines characteristics of both petrol and diesel engines to improve efficiency.
Mazda’s new SKYACTIV-X engine between a petrol and diesel powertrain
A traditional petrol spark ignition engine uses a spark plug to ignite the air-fuel mixture which causes the combustion flame to spread from the spark and burn gradually.
Diesel compression ignition directly sprays feel into the compressed and heated air. From there the mixture burns rapidly and simultaneously from multiple points.
Mazda’s new powertrain uses Spark Controlled Compression Ignition which generates a fireball with a spark plug, much like a petrol engine, but combusts rapidly and at multiple points like a diesel.
Additionally the compression ignition pushes the piston down longer and stronger.
The car manufacturer claim that this is world’s first commercial gasoline engine to use compression ignition.
This engine challenges the commonly-held belief that a large engine displacement means poor fuel economy
In the video you see that there is a short burst of fuel from the injector, which combines with the intake air which mixes in a clone creating a lean fuel mixture in the cylinder.
It enables more efficient combustion which allows the car to achieve “superior environmental performance, response and acceleration.”
Mazda claims that the car combines the best characteristics of both petrol and diesel.
Here’s how Mazda describes is: “The SKYACTIV-X controls the distribution of the air-fuel mixture in order to enable lean burn using the SPCCI mechanism.
The goal and factors need for the perfect engine
“First, a lean air-fuel mixture for compression ignition is distributed throughout the combustion chamber.
“Next, precision fuel injection and swirl is used to create a zone of richer air-fuel mixture—rich enough to be ignited with a spark and to minimize nitrous oxide production—around the spark plug.
“Using these techniques, SPCCI ensures stable combustion.”
It allows the higher torque, response and fuel economy of diesel but also the output (expansion), heating and exhaust purification of petrol.
The elements that the SKYACTIV X borrows from both petrol and diesel engines
Theoretically improving each on of these individuall elements will improve the overall efficiency of the engine.
Therefore these cars are going to be more efficient but also have improved acceleration.
“With an engine displacement of 2.0L, the SKYACTIV-X delivers at least 10 percent more torque than the current SKYACTIV-G, and up to 30 percent more at certain rpms (data as of August 2017, during the development process).
“In addition, because the throttle valve is open most of the time, it exhibits the superior initial acceleration response found in diesel engines which do not have a throttle valve. On the other hand, the SKYACTIV-X spins up into the higher rpm ranges as smoothly and easily as a typical gasoline engine.”
“In a vehicle with a 2.0L engine displacement, the SKYACTIV-X delivers a 20 percent improvement in fuel economy compared to the SKYACTIV-G, a dramatic increase.
“Furthermore, in areas where low vehicle speeds are used frequently, fuel economy can be improved by up to 30 percent thanks to the use of super lean combustion.
“Compared to the MZR engine of 2008, fuel economy is improved a dramatic 35-40 percent, and SKYACTIV-X even equals or exceeds Mazda’s latest diesel engine, SKYACTIV-D, in fuel efficiency.
“With improvements being especially great in the light engine load range, this engine challenges the commonly-held belief that a large engine displacement means poor fuel economy.”