On March 10, '23, Great Wall unveiled its next-generation hybrid technology, Hi4.
This technology is structurally very different from existing hybrids, and can realize electric four-wheel drive for new energy vehicles at a very small cost, allowing consumers to buy a four-wheel drive vehicle for the cost of a two-wheel drive vehicle and making the popularization of electric four-wheel drive vehicles possible.
Great Wall Motor even directly shouted the slogan: "Bring Chinese cars into the era of universal electric four-wheel drive. "
Electric four-wheel drive for all? Doesn't that mean we're going to "kill" the 2WD and make it history?
What a mouthful!
I'm sure you've got a lot of questions at this point, such as: How is the Great Wall Hi4 different from other hybrid technologies? How is its low-cost electric 4WD realized? What cars will come with Hi4 and how much will they sell for?
Don't worry, let's analyze it bit by bit.
The basic structure of a hybrid car
Broadly speaking, a car that burns oil and runs on electricity can be called a hybrid. But different manufacturers often have different ideas about how to accomplish this.
For example, differences in the placement of the electric motors can have a big impact on the structure and effectiveness of the hybrid system.
Based on the position of the motor, it can be categorized into several layouts such as P0~P4. The diagram below gives a good idea of the differences in the motors between the different layouts.
P0 motor: Located at the belt end of the engine, it is driven by the belt, with small power and torque, and is mainly responsible for engine startup assistance as well as power generation. In the auxiliary drive, the power is transmitted through the belt, the role is limited;
P1 motor: located in the engine flywheel end, before the clutch, driven directly by the engine crankshaft, the power is larger than the P0 motor but limited, the function is basically the same as the P0 motor, but in the auxiliary drive, the power is transmitted through the crankshaft, the role is greater than the P0 motor;
P2 motor: located after the clutch, before the transmission, not with the engine in the same shell, so the volume can be larger, power can be higher. Also because it has a clutch between it and the engine, it can drive the wheels alone without driving the engine crankshaft, making pure electric drive possible. However, because the power also has to pass through the transmission, there is still a certain loss of power transmission;
P3 motor: located after the transmission, can be arranged in a richer space, so the power can be further improved. At the same time, the power output can be driven directly to the wheels without passing through the transmission, and the efficiency is higher when driving purely electrically, so it is mainly used as a drive motor, and is not responsible for generating electricity;
P4 motor: not on the same axis with the engine, usually located in the rear axle, and there is no power connection between the engine and the front axle to realize the coupling through the ground.
P4 motor: is used in performance cars, to realize power supplementation. used in performance cars to realize the power supplement, but also with the front axle to realize the electric four-wheel drive.
It is easy to see that P0~P4 motors have their own characteristics. And the differences in hybrid technology between different manufacturers can be seen simply as a combination of different motors.
For example, BYD's DM-i is a hybrid system with P1+P3 motors. The P1 motor is mainly used as a power generator, while the P3 motor is mainly responsible for driving the wheels. There's a clutch between the engine and the output shaft, through which you can disconnect or connect the engine's output, switching between pure electric/parallel/direct-drive modes.
Photo credit: Zhihu Wang Yuanqi
The advantages of this system are obvious: no gearbox, simple structure, and low cost. At low speeds, the clutch allows the engine to drive only the P1 motor to generate electricity, keeping it working in the optimal efficiency zone for a long time, and then driving the wheels through the P3 motor, realizing an add-on series hybrid. And at high speeds, it can again be engine-driven directly, reducing losses due to kinetic energy transfer, and can also be driven in parallel with the P3 motor to bring better power.
It can be seen that the biggest advantage of this system is energy saving, but there is also a shortcoming: because there is no gearbox, the engine and P3 motor **** with a reducer, the engine is equivalent to working in a single gear in direct drive and parallel, so the DM-i's engine only reaches a certain speed (the official data is between 60-70km/h) can direct drive or parallel drive.
This prevents the DM-i from fully utilizing the engine's power at low and medium speeds, and the vehicle's power performance is average. At the same time, it's also difficult to realize electric four-wheel drive because the entire powertrain is on the front axle.
Because of this, BYD then launched the MD-p, which adopts the structure of P0+P3+P4:
Because of the addition of the high-power rear-axle P4 motor, the vehicle's performance has been improved through the form of dual motors, while electric four-wheel drive has also been realized, but at the expense of the cost and selling price, which has also been significantly increased.
Back to the Great Wall. Their "Lemon Hybrid" also uses the P1+P3 layout, and also supports series-parallel hybridization, but adds a hybrid-specific two-gear transmission after the clutch, which is often referred to as the "DHT".
Photo credit: Wang Yuanqi of Knowledge
Because of this two-gear DHT, the Lemon Hybrid can realize a 2-gear direct drive/parallel drive, which allows the engine to intervene in parallel mode in time at low and medium speeds (official data is about 40km/h), significantly improving the vehicle's power performance at low and medium speeds.
However, this still doesn't solve the problem of the P1+P3 layout making it difficult to realize four-wheel drive, so Great Wall has introduced a four-wheel-drive-specialized hybrid configuration - Hi4 - on this basis.
What's the difference between Hi4 and other hybrids?
Unlike existing hybrid systems, the Great Wall Hi4 adopts the P2+P4 hybrid configuration, which means that the front axle motor is located after the clutch and before the transmission; the former P3 drive motor is now "moved" to the rear axle as the P4 motor.
The unique layout of the motor gives the Hi4 the following features:
1: the front axle motor can drive the wheels directly, and does not drive the engine crankshaft, which is less lossy;
2: the power output of the front axle motor is also routed through the 2-speed transmission, which allows switching of high torque/high RPM;
3: the engine can also be driven directly through the clutch, and the 2-speed DHT can be used for low and medium speeds. 2-gear DHT can realize the intervention parallelism in low and middle speed;
4: through the clutch, the engine drives the front axle motor to generate electricity, and the rear axle motor is driven independently to realize the tandem (range-extended) pure electric rear-drive;
5: the front and rear motors work at the same time to realize the pure electric four-wheel-drive; the engine can also be paralleled with four-wheel-drive after start-up to realize the full power release of the system.
It's not hard to see that the biggest highlight of Hi4's P2+P4 configuration lies in the realization of four-wheel drive without increasing the number of motors, making the overall cost controllable and the popularization of four-wheel drive technology possible.
Some may ask: What's so great about 4WD, why must it be included?
We know that four-wheel drive is what gives power to all four wheels of a car, giving the vehicle better handling and passing power. But traditional fuel vehicles often require complex mechanical transmission structures to realize four-wheel drive due to a single power source (the engine), and this can make the cost much higher, so only some models can carry it.
After the car is electrified, the power source becomes an electric motor, and only two motors at the front and rear are needed to easily realize the car's electric four-wheel drive.
At the same time, the Hi4's electric four-wheel drive is different from traditional four-wheel drive because it doesn't rely on mechanical transmission, so the power (torque) output of the front and rear axles can be flexibly adjusted to further improve the car's maneuverability and drivability.
And the existence of electric 4WD also allows the power output not to be limited to a certain axle, based on the grip of all four wheels, to realize better performance release, and to reduce skidding due to excessive torque and power overload.
In addition, the motor has an "optimal operating range" for energy recovery, and energy recovery at high speeds may break through this range, resulting in a waste of energy. The Hi4 makes full use of the motors on both axes to achieve dual-axis energy recovery and single-axis energy recovery, which results in more efficient energy recovery and a longer range.
In this regard, I just want to say: Four-wheel drive will become one of the core advantages of automotive electric drive.
But the Hi4's P2+P4 configuration faces many difficulties to realize. The first and foremost is the arrangement of the P2 motor.
The space between the clutch and transmission is limited, and to put a traditional motor here, you have to make a trade-off between size and power. The Great Wall Hi4 technology, however, directly integrates the P2 motor and electronic control in the DHT transmission, forming a set of "DHT electric drive assembly".
This "DHT electric drive assembly" is tightly integrated with the engine through the gear structure, which not only saves axial space, but also further compresses the manufacturing cost, and becomes the key to the Hi4's low-cost four-wheel drive.
On the other hand, in order to realize high power in a limited volume, Hi4's motor also adopts Hair-pin flat wire winding, variable lubrication flow control, low-resistance high-efficiency bearings and other technologies, which enable its motor to reach a maximum efficiency of 94.3% and a maximum power of 80kW (with an additional 70kW low-power version).
Which cars will come with the Hi4 hybrid? How much will it cost?
The launch event said the first Hi4 hybrid-equipped car will be a new Haval vehicle, which was officially unveiled at the end of March. According to Haval's previous pricing strategy and the Hi4 hybrid's technological positioning of "technology for all", there is no doubt that it will be aimed at the most mainstream market, after all, the Great Wall's boasts have already been put out: "2WD price, energy consumption, 4WD performance, experience", perhaps we can look forward to the price of the car.
We can look forward to the price of the car, and perhaps the price of the car.
Additionally, according to the pre-launch media conference, the Hi4 will have two powertrains:
Low: 1.5L engine + 70kW transmission + 150kW rear axle motor;
High: 1.5T engine + 80kW transmission + 150kW rear axle motor.
Meanwhile, the battery pack will also be available in two capacity specifications of 19.94kwh/27.5kwh, with the entire vehicle's pure electric range up to 100+km, and the system's power range up to 220kW~350kW, covering the A/B/C class.
It is foreseeable that not only Haval, Hi4 hybrid will be applied in more brands. And Haval, as the mainstay of the Great Wall brand, is indeed the sales platform most likely to realize the rapid popularization of the technology.
While the entire market is cutting back and lowering costs to fight a price war, Great Wall is adding to its products through technology, hoping to capture the market through a leap in product power. This is undoubtedly a risky move, but it also shows Great Wall's determination.
From a technical point of view, the Hi4's advantages are obvious, and the many features of the electric four-wheel drive make it possible to significantly improve the vehicle's maneuverability, drivability and safety. More critically, the cost of this system is not too far removed from the existing two-wheel-drive lemon hybrid, and will be essentially the same in terms of end-product pricing.
But at the market end, there's still the question of what consumers will choose between a price cut and electric 4WD.
The market will tell us the answer.
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