An Initial Exploration of the AITO M9 Range-Extender Engine Technology

The topic surrounding the AITO M9 is very lively at present, but few people pay attention to its range-extending engine. How can such a highly discussed car have a key component in its power system remain relatively unknown? I believe the current focus of promotion is on intelligence and electrification. Even when discussing range-extending technology, the engine is often downplayed, as mentioning it might evoke associations with traditional car companies.
 

In fact, to a large extent, the key technology in range-extending systems lies within the engine. Today, let's take a closer look at the technical aspects of this range-extending engine.
 

The AITO M9 range-extender version is equipped with a four-cylinder turbocharged 1.5T engine, code-named H15RT, and a hybrid system consisting of dual motors. This 1.5T engine was developed specifically for AITO by Xiaokang Power, and its maximum engine power is 112kW.
 

In fact, this range-extending engine is also used in the AITO M7, making it a relatively mature option commonly found in AITO models. This engine has several distinctive features:
 

The technical configuration is optimized to maximize efficiency, while other configurations focus on maturity and reliability.
 

1. Deep Miller Cycle Combustion System: This engine employs a deep Miller cycle combustion system. The Miller cycle enhances thermal efficiency by closing the intake valve early, resulting in a combustion method with a larger expansion ratio than the compression ratio. This allows the physical structure’s compression ratio to be higher without causing knocking. The 1.5T engine in the AITO M9 utilizes a very high physical compression ratio of 15:1, maximizing thermal efficiency.
    

   
    

2. Single VVT Design with Central Oil Pressure Control Valve: The early intake valve closing in the deep Miller cycle requires a variable valve timing (VVT) system with a wide adjustment range and fast response. This 1.5T engine uses a single VVT setting on the intake side, controlled by a central oil pressure control valve, offering a larger adjustment range and quicker control response. However, it lacks an exhaust-side VVT, which is unnecessary for a range-extending engine focused on mid-load efficiency rather than high-speed performance.
    

3. EGR (Exhaust Gas Recirculation) System: The engine also features an EGR system, which recirculates a portion of the cooled exhaust gas back into the cylinder. This reduces the likelihood of knocking and minimizes pumping losses at low loads, effectively improving thermal efficiency. The AITO M9's 1.5T engine can achieve an EGR rate of up to 30%, which is near the maximum for maintaining stable combustion.
    

   
    

4. Beltless Front-End Design: To reduce friction, the 1.5T engine uses a beltless front-end design. Traditionally, belts drive the water pump, generator, and air-conditioning compressor. However, for a range-extender system, the generator is unnecessary, and the air-conditioning compressor can be electrically driven. This engine uses an electronic water pump, eliminating the need for a traditional belt system, thereby reducing friction and improving efficiency.
    

   
    

5. Port Fuel Injection (PFI): This engine employs port fuel injection (PFI) instead of direct injection, reflecting a conservative yet suitable choice for a range-extending engine. Direct injection offers performance advantages at high speeds and loads, but those benefits are irrelevant for a range-extender, which primarily operates at medium loads for maximum efficiency. Additionally, PFI avoids the noise and resistance associated with direct injection and does not produce particulate emissions, simplifying the exhaust system and reducing costs.
    

   
    

6. Cast Iron Cylinder Block: The use of a cast iron cylinder block in this 1.5T engine is notable. While heavier than aluminum, cast iron offers greater stability and reliability. Xiaokang Power’s expertise in iron cylinder casting likely influenced this choice, as it maximizes resource utilization and cost-effectiveness.
    

   

Summary: The technical configuration of AITO’s 1.5T range-extending engine is unique. It incorporates all technologies that enhance range-extending efficiency while relying on mature, even conservative solutions elsewhere. This engine is not the main component of the power system; it is designed to consistently and efficiently convert energy, leaving the rest to the electric motors. This strategy is likely to become the mainstream approach in developing future range-extending engines.