Others have already tried the technology of a “Diesotto”. Now it really should work: In 2019 Mazda wants to bring an engine on the market, which combines the advantages of a gasoline engine with those of a diesel. This drive should be economical, and at the same time clean. “Skyactiv X” is the name of the self-igniting petrol engine, which the Japanese attest to a 20 to 30 percent reduction in fuel consumption.
Experts estimate that by 2025, about 30 to 40 percent of cars will be electrified. Conversely, this means that 60 to 70 percent still use conventional drive. In other words, the good, old internal combustion engine is far from dead. To make it fit for the future, it is important to ensure greater efficiency and better emissions. Mazda pursues a recipe that experimented with the experimental kitchen of Mercedes more than ten years ago. The test vehicle F700 at that time a 238-hp “Diesotto” was planted, which represented a cross between gasoline and diesel. And VW has already tested a CCI drive (Combined Combustion System).
Efficiency and driving pleasure
The charm of such a design principle is to combine the best of two worlds-that is, the efficiency and higher torque of a diesel with the driving enjoyment promising revolutions of a gasoline engine, which needs thanks to its lower pollutant emissions (NOx) on top of any costly measures of exhaust aftertreatment.
Mazda’s new petrol-diesel hermaphrodite is called Skyactiv X, the X stands for “Cross”, so the intersection of both types of drive. First, the 190 hp two-liter four-cylinder for the year-end debut next Mazda 3 can be ordered, but probably only in March 2018. Compared to the conventional petrol engine Skyactiv X is about 20 to 30 percent less gas consumption and thus approximately on diesel Level are. The pollutant emissions, Mazda promises, would be so low that the strict Euro 6d Temp standard will be met without any problems. Also, a particle problem is not, and it is still unclear whether this is an Ottopartikelfilter (OPF) plays a role.
On the technical principle: When gasoline engine, the gasoline-air mixture is known to be exploded by a spark, alien ignited so. In the case of diesel, on the other hand, the air is heated to such a high degree by high compression in the combustion chamber that the fuel ignites completely without a spark plug. Therefore one speaks of the diesel. The diesel-petrol hermaphrodite pursues a compromise here: At start and under full load-if the driver demands so much power-there is a spark ignition. In the partial load range, ie at low and medium speeds, the Diesotto works with extraneous or compression ignition. It is necessary because you want to use a particularly “lean” mixture (a lot of air, little fuel) in terms of economy, for which a combustion process with spark plug is unsuitable because it would run unstable.
Weak points wiped out
At this point, others had already arrived. However, so far it has not been possible to overcome the weak points of the technology. For example, the transition between the foreign and auto-ignition phases was out of round, sometimes even with dropouts. In addition, the operating range in which self-ignition or compression ignition took place was ultimately too small.
Mazda has solved the problem by using the spark plug in all areas of operation-not only in the spark-ignition, but also in the auto-ignition phase. However, the task of the spark is then only to ignite a small amount of “rich” mixture injected directly into the center of the cylinder, thereby increasing pressure and temperature to such an extent that the lean mixture in the environment can ignite itself. The technology is called “SPCCI”, Spark Controlled Compression Ignition.
On the way on first test drives
Just over a year before the market launch, Mazda has now asked for the first test drives with the Skyactiv X engine, which hid under the hood of a still current Mazda 3 in a discreet matte black. And he leaves a good impression, the prototype. He acts calmly, quiet and noticeably more relaxed than the comparatively provided conventional Skyactiv G-petrol engine. Overall, Mazda’s “Diesotto” is already astonishingly mature. This applies both to the combination with automatic as well as with the 6-G handset, which did not have to be overstretched thanks to the offered elasticity.
The transitions between the operating phases with external and compression ignition are gentle and imperceptible, the change was only on the tablet, sitting on the dashboard of the test vehicle. Only in energetic interim sprints we slipped into the more fuel-intensive spark ignition operation for a short time, otherwise we moved virtually throughout the more efficient compression ignition mode. What this actually meant for consumption, however, could not be determined, because Mazda had deprived the test vehicle of the corresponding ad.
For the buyer, the decision for the Skyactiv X is associated with a certain additional investment compared to the conventional petrol engine. It is conceivable a surcharge of about 1,900 euros, which would move but still below the diesel regions.
Electric Mazda in sight
Mazda wants to know his “Diesotto” as an alternative to the diesel, not as a replacement. From this one may conclude that the D-engine can do a lot better at the moment. Torque, for example, which is why in larger vehicles-such as Mazda’s Topseller CX-5-still finds its justification. In 2020, the Japanese introduce a fundamentally renewed diesel generation. And in 2019 their first battery electric vehicle, of which there will also be a variant with Wankel engine as a range extender. If around 2025 well half of the cars are electrified, Mazda does not want to be out.
