K12C Dualjet engine

New Suzuki Solio Launch: New engine offers world’s top-class thermal efficiency, and what lies ahead

The all-new Solio and the all-new Solio Bandit launched by Suzuki on August 26 is a two-row compact van equipped with a naturally aspirated 1.2-liter engine called the K12C engine. This is a DualJet engine, which comes with two fuel injectors per cylinder.

The K12C generates the same maximum output and maximum torque of 91ps/6000rpm and 118Nm/4000rpm as the Swift’s K12B Dualjet engine, but it has higher thermal efficiency, which is the measure of how much thermal energy in the fuel is converted to motive power. From the conventional models’ all-time high thermal efficiency of 37.1%, the K12C has 38%, a world-class thermal efficiency for mass-produced gasoline engines barring the Miller cycle engines.

It should be noted that when running in JC08 mode, the average thermal efficiency of that peak value was raised from 34% to 35%. The Solio uses an auxiliary transmission, and the Jatco CVT realizes an ultra-wide transmission ratio, but that alone does not make it possible to reach the 35% thermal efficiency. To achieve this, the engine needs to have a higher thermal efficiency as well.

The K12C is the improved version of the K12B, and the changes made to its design was pretty extensive. Its compression ratio has been raised from 12:1 to 12.5:1. The optimized shape of the intake port creates a strong intake vortex that improves the cooling performance of the cylinder heads, while suppressing abnormal combustion. Through the adoption of roller rocker arms and the decreased frictional resistance because of the lowered tensile strength of the auxiliary equipment belt, steady refinement is done thoroughly.

Suzuki has set a goal to have an average thermal efficiency of 40% in JC08 mode by 2020. This is an extraordinary numerical value because it rivals the current high-performance diesel engines.

Originally, 40% was a difficult target to reach. We have finally reached 35%, so the difficulty to get better efficiency will be on a different level from this point forward. Of course, we will not set a target that can be achieved easily. Thus, naturally, this is a challenge for us.”

The statement above was said by an engineer who worked in the development of the K12C engine.

“Moreover, one of the most important ways to help increase thermal efficiency is to effectively use the lean-burn. With that, another challenge we face would be how to filter the exhaust gas,” he added.

Suzuki still has more room to potentially raise the thermal efficiency because unlike their rivals, they haven’t used the Miller cycle and other technologies such as direct injection yet. With their partnership with Volkswagen ending in dissolution, Suzuki will single-handedly develop their engine technology to survive the competition, and it is noteworthy to see how they will advance their progress.

(Translated by Katherine N. Bantiles)