When it comes to "rolling" hybrid technology, if the Chinese claim to be second, it's likely no one would dare to claim first. Yesterday, Changan Automobile unveiled three engines in one go, which are divided into a 1.5L naturally aspirated engine, a hybrid-specific 1.5T, and a purely gasoline version of the 1.5T. The first two are dedicated hybrid engines. I've actually known the specifications of these engines for a while, but due to confidentiality, I had to wait until today to share them with you. Today, I mainly want to share with you the hybrid-specific engines.

Knowing that you like to see the numbers, the rated power of the 1.5T hybrid-specific engine is 110kW, with a maximum torque of 220N·m, and an impressive thermal efficiency of up to 44.28%. The naturally aspirated 1.5L version is also for hybrid use, with a rated power of 72kW and a maximum torque of 125N·m, and a mass-produced thermal efficiency that can reach 43.31%.

On the technical front, the engines released by Changan this time also employ many industry firsts.

Firstly, the engines meet the stringent national VI b-RDE emission standards without the use of a GPF (Gasoline Particulate Filter). The two most stringent emission standards in the world are those of Europe and China. This particulate filter acts like a "garbage collector," trapping pollutants in the exhaust before it is released into the atmosphere. However, it has a drawback: it can hinder the smooth release of exhaust gases, and in severe cases, it can even cause blockages, leading to a decrease in engine power or even malfunctions. Volkswagen has previously suffered from this issue. Changan's ability to do without a particulate filter this time indicates that these machines have made significant efforts in the combustion section, striving to ensure complete gas combustion and preventing harmful gases from being emitted outside the vehicle.

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How can gasoline burn more completely to extract every last drop of energy from it? Changan has taken the lead in using a 500Bar direct injection system.

500bar fuel injection system

The current industry standard is 350bar, so how powerful is 350Bar? 1bar is equivalent to 1.01972 kgf/cm² (kilograms-force per square centimeter), so 350bar is like stepping on a 350-kilogram calf with the area of a fingernail. Therefore, 500bar is equivalent to a 500-kilogram bull. The higher the bar number, the better the atomization of the gasoline, and the better the atomization, the more complete the combustion.

In other aspects, the most advanced 150mj high-energy ignition is used, which allows for more stable and lasting spark plugs, often used in conjunction with low-pressure EGR to improve unstable combustion. EGR can reduce nitrogen oxide emissions and improve fuel economy. Additionally, this engine boasts an impressive stroke/bore ratio of up to 1.45! Therefore, the compression ratio reaches an ultra-high 16:1 (for turbocharged direct injection engines: 15:1).

Of course, there are many other advanced technologies in such hybrid-specific engines. Due to time constraints at the Changan press conference, aspects such as low friction and thermal management were not mentioned. Next, let's look at what technological points a "hybrid-specific engine" needs to have.

Why do we need hybrid-specific engines?Coincidentally, at the launch event of Yao Guang C-DM, we observed that Chery's Exeed brand introduced the concept of "full domain dedicated hybrid". The four major components, including the dedicated hybrid platform, transmission, engine, and battery, were developed from the outset with hybrid power in mind, rather than being mere modifications of existing systems.

Why is a full domain dedicated hybrid necessary? We need to discuss the entire evolution of hybrid power.

The first generation is characterized by oil-to-electric conversions, with most having a range of less than 50km, high fuel consumption, poor experience, and low reliability, often leading to breakdowns. Their feature is the rudimentary addition of a P2 motor between the engine and transmission. Despite the presence of a motor, they still fundamentally rely on the engine.

The second generation is primarily oil-based, with significantly improved reliability, further reduced fuel consumption, but issues with noise and range remain unresolved. For instance, the first-generation I-MMD and THS 2.0 systems typically have batteries of about one degree of electricity. The original intention is still oil-centric, where the motor's role is to keep the engine operating in its most efficient range, akin to "peak shaving and valley filling."

The third generation is primarily electric-based, achieving breakthroughs in range and energy consumption, with most adopting single-gear technology. However, problems such as high fuel consumption at high speeds, susceptibility to speed loss, and insufficient intelligence persist. For example, DM-i adds a larger battery to the i-MMD foundation and increases the power of the drive motor, making the vehicle more electric-like at medium and low speeds, but the issue of speed loss at high speeds still exists.

The fourth generation is characterized by a full domain dedicated hybrid. For instance, the Chery CD-M we see now features a dedicated engine with a more significant breakthrough in thermal efficiency; a multi-gear DHT transmission is more conducive to high-speed driving; dedicated M3P batteries address the inherent shortcomings of lithium iron phosphate and ternary lithium batteries, offering better low-temperature performance and higher energy density; a dedicated architecture allows the battery and fuel tank to be fully enclosed in the central part of the vehicle body, avoiding dangers in the event of rear-end collisions.

What technologies are needed for a hybrid-specific engine?

As a fuel-efficient engine, the most we hear about are "Atkinson cycle" and "Miller cycle," and later you might even hear about the more detailed "deep Miller cycle." The main principle is to have an expansion ratio greater than the compression ratio, achieved by controlling the intake valve to close earlier, thus accomplishing "doing more with less." By the way, the Atkinson cycles on the market are not truly Atkinson cycles in the true sense; they are essentially "Miller cycles" that achieve the "effect" of the Atkinson cycle through electronic control. Generally speaking, to be in the first tier of hybrid-specific engines in China, the compression ratio must reach at least 15-16, and the thermal efficiency must reach at least 43% before you can talk about your technology.

The Miller cycle is just a foundation, but it is not yet a dedicated hybrid engine.

A hybrid-specific engine will have a multitude of technologies serving thermal efficiency, such as the deep Miller cycle we just mentioned, which creates a larger expansion ratio and compression ratio ratio by creating a larger intake valve closing angle (IVC). It is understood that the deep Miller cycle can increase the thermal efficiency by about 1.5% compared to the conventional cycle.Low-Pressure EGR

Low-Pressure Exhaust Gas Recirculation (EGR) is a common component in hybrid-specific engines, often used in conjunction with high-energy ignition systems, such as those employed by Changan and Chery. Different manufacturers have their own names for low-pressure EGR, such as "full-range coupling" or "wide-range cooling." The low-pressure EGR, which draws in exhaust gases ahead of the turbocharger, can achieve a higher EGR rate, with Chery's data suggesting it can reach approximately 25%-27%. In layman's terms, this means more exhaust gases are recirculated, which can reduce combustion temperatures, resulting in less heat loss, more work done, and reduced likelihood of knock. Compared to high-pressure EGR, which draws gases after the turbocharger, it can save 0.5-1% on fuel consumption and increase overall thermal efficiency by 1.5%.

High-Pressure Fuel Injection and Fully Variable Oil Pump

High-pressure fuel injection is a well-known technology that has been previously mentioned, so I won't delve into details here. With Changan's pioneering use of a 500bar direct injection system in China, it is expected that such systems will become increasingly common in domestic hybrid-specific engines in the future.

Regarding the oil pump, due to the different operating modes of hybrid engine compared to conventional gasoline engines, we typically see two types: two-stage variable and fully variable oil pumps. A fully variable displacement oil pump more closely matches the demand for oil, with lower oil pressure, less mechanical work consumed by the oil pump, fewer additional losses, higher effective power output, reduced mechanical losses in the engine, and improved mechanical efficiency.

High Tumble Ratio Intake Port

With high-pressure fuel injection, a high tumble ratio intake port is essential. The tumble ratio refers to the ratio of the rotational speed of the swirling mixture in the combustion chamber to the engine's rotational speed. A higher value indicates greater kinetic energy of the airflow within the cylinder and more complete combustion of the mixture. Achieving a high tumble ratio involves several factors, such as the design of the intake port, the top of the piston, and the cylinder head design.

Turbocharging

Turbocharging is a crucial element in energy-saving and efficiency enhancement. Most turbochargers in hybrid-specific engines are now electronic, featuring low inertia, fast response, and precise electronic control. Regarding these hybrid turbochargers, Haohan Mach D-Hybrid has also proposed the concept of a hybrid-specific VGT (Variable Geometry Turbocharger) technology, which essentially means that this geometrically variable section turbine is more suitable for hybrid vehicles, offering greater energy-saving and efficiency.Intelligent Thermal Management

Similarly, based on the working characteristics of the engine specifically designed for hybrid powertrains, which operate intermittently and at relatively stable speeds, electronic water pumps are generally used to replace mechanical water pumps. The fully electronic water pump is decoupled from the engine speed, allowing for demand-based water supply. For instance, during a cold engine start, it can reduce the water flow to quickly warm up the engine, thereby reducing friction.

I will stop here for now regarding the content on engines specifically for hybrid powertrains. There is actually much more to discuss, and it would take a whole day to cover everything in detail. I have only selected a few points to talk about. Moving forward, I will also discuss the topic of hybrid-specific transmissions.