Recently, the hot spot in the automotive industry has changed from intelligence to the battle of "whose engine thermal efficiency is the highest". When it comes to engine thermal efficiency, it seems to have been Japan's strong point for a long time. In the era of internal combustion engines, Japanese brands have indeed made a lot of contributions to improving thermal efficiency, such as Toyota's VVT-i technology, Honda's i-VTEC, Nissan's VC-Turbo and other technologies, all of which were created to improve thermal efficiency. In pure fuel vehicles, the thermal efficiency of the engine basically reaches the ceiling at 41%, and it is difficult to break through. This is because the engine of pure fuel vehicles has to take into account different working conditions, and it is difficult to stabilize in the high-efficiency range, and there are many things that the engine has to take into account, such as driving the generator, oil pump, starter, valve timing system and other complex equipment, which can only sacrifice part of the thermal efficiency. In the era of plug-in hybrids, this has changed completely.
BYD's DM-i technology hands over the main task of driving to the motor, and the charging utilizes the characteristics of the motor with low rotation and high torque and high drive efficiency, while the engine retreats to the role of a range extender, and only generates electricity at low and medium speeds, and the power required by the vehicle is not high when the vehicle is in high speed, and the engine can work in the high-efficiency range at this time. BYD also put forward the concept of "plug-in hybrid engine" for the first time, and the engine canceled the front-end gear train, medium and low-speed power generation, and high-speed direct drive, realizing the ideal goal of the engine always working in the high-efficiency range. Under this working logic, the thermal efficiency of the fourth-generation DM released in 2021 reached 43.04%, making it the engine with the highest thermal efficiency in mass production at that time.
On May 28, BYD released the fifth-generation DM technology, the most eye-catching of which is that the thermal efficiency of the new engine has reached a new high, reaching 46.06%. The Qin L and Seal 06 DM-i, which are the first to use the fifth-generation DM technology, can achieve fuel consumption of 2.9L/100km (NEDC mode) and a range of more than 2,100km.
The fifth-generation DM technology is a monolithic, including important upgrades to the three-electric system and thermal management, and the new 1.5-liter self-aspirated engine is also evolving, with a compression ratio of an astonishing 16:1. Such a high compression ratio is easy to produce detonation, BYD through the EGR exhaust gas recirculation system, in the air intake system to properly introduce the exhaust gas discharged from the last cycle, can effectively control the temperature, so as to avoid detonation. The new 1.5-liter engine has reduced its peak power and torque again, with a maximum power of 74 kW and a maximum torque of 126 Nm, which means that the engine will stay in the high-efficiency range for a longer time. Under a simple analysis, the power demand of the general compact car at 100km/h cruising is about 30kW, the power of the engine is very rich when the engine is directly driven, and the speed is controlled in the most efficient range of 2500-3000rpm, and the power when generating electricity is generally enough at 10kW, and the speed is easier to control. Of course, this premise is that the power and torque of the motor are sufficient, and the discharge capacity of the battery is not lagging behind.
Interestingly, on May 29, the day after BYD's press conference, Geely Automobile released a product certification certificate, which was issued by China Automotive Research Huacheng Certification (Tianjin) Co., Ltd. on July 21, 2023, showing that Geely's BHE15-CFZ engine has a thermal efficiency of 46.1%. We estimate that this is the test data of Geely's latest generation of Thor plug-in hybrid engine, and it is also a very good performance. Looking back at the thermal efficiency of Raytheon's 1.5T engine, it reached 43.32% two years ago and 44.24% last year, both exceeding the 43.04% of the fourth-generation DM Xiaoyun 1.5L engine.
From the perspective of Chinese cars, this is not a bad thing, Chinese cars should compete more in these hard technologies, but less to fight refrigerators and color TV sofas. However, we also have to point out that Geely's engine, which has a thermal efficiency of 46.1%, is still in the laboratory stage, and no specific loading time has been given. If you look at the data of the laboratory, BYD also has a certificate of engine certification with a thermal efficiency of 46.5%. Mazda's Skyactiv-X engine has a thermal efficiency of 48 percent, while Nissan's latest e-POWER range extender engine achieves 50 percent. Since there is still a lot of reliability verification to be done from the laboratory to mass production, and the cost factor is also considered, we believe that the energy production and practical technology is meaningful for users.
In fact, since the success of BYD DM-i plug-in hybrid technology, most of the domestic independent brands have basically followed, and the thermal efficiency of the plug-in hybrid special engines launched by mainstream car companies is relatively high, after all, they have deep technical accumulation in the engine field. But after all, BYD was the first to eat crabs, and its leading role is immeasurable. We hope to see Chinese brands scrambling to be the first on the road of pursuing technology, forming a good atmosphere of taking technology as the core and speaking with products, and correcting the crooked trend of boasting and exaggerating and over-marketing.