Computing Life

Recently, I've been part of some fascinating discussions in a WeChat group about the chassis and handling design of internal combustion engine (ICE) cars versus electric vehicles (EVs). Having done some research on this topic out of personal interest, I saw this as a perfect opportunity to consolidate my knowledge and subjective opinions. This is partly for my own future reference and partly to spark some new ideas for everyone.

Online debates about the handling of EVs versus ICE cars often swing between two contradictory extremes. On one hand, there's the disruptive narrative of new technology. From active suspension systems like BYD's DiSus to electronically controlled all-wheel drive with multiple motors, EVs seem to crush ICE cars in specific metrics. On the other hand, there's the real-world driving feedback. Many experienced drivers, especially performance car owners, feel that the actual driving experience of EVs, particularly in terms of the "at-one-with-the-car" feeling, still lags behind excellent ICE cars.

This used to puzzle me. How should we view this disconnect between technology and experience? Is it just marketing hype from EV manufacturers, or is it the bias of ICE car owners who can't feel satisfied without the roar of an engine? What are the fundamental differences in vehicle dynamics and chassis engineering between EVs and ICE cars?

This article is my attempt to answer these questions. I want to start from first principles, first exploring the ultimate goal of chassis engineering as a systemic task. Then, I'll analyze the tools engineers have at their disposal to achieve these goals. Finally, I'll place EVs and ICE cars within this framework to understand why they have taken such divergent technological paths. It's important to note that I'm not an industry professional. These views are based on my research, thoughts, and conversations with friends, so there will inevitably be shortcomings. Consider this a starting point for discussion.

Chapter 1: The Goal of Chassis Engineering—Finding the Sweet Spot in a Triangle of Compromise

To evaluate a chassis system, we first need to define the criteria. I've always believed that engineering is about trade-offs. The ultimate goal of chassis engineering is to find the optimal balance among three mutually constraining core objectives, based on the vehicle's intended positioning. These three objectives can be seen as the vertices of a triangle: comfort, handling, and stability.

1. Comfort: Isolating Vibrations. Comfort is the most fundamental task of chassis engineering and the original reason for the invention of the chassis and suspension. Modern chassis systems are often designed to dampen vibrations at specific frequencies that are particularly sensitive to the human body, roughly 4 to 8 Hz vertically and 1 to 2 Hz horizontally. A comfort-oriented chassis system's core mission is to use tools like springs, dampers, and bushings to absorb and filter out vibrations in these frequency bands as much as possible, isolating the occupants from the bumpy road.
2. Handling: Responding to Intent. Once a chassis meets the comfort requirements, it's already a competent family car. But many performance-oriented drivers want more in terms of handling—the ability to "point and shoot." This includes precise and linear steering feedback, agile and controllable body response during acceleration, braking, and cornering, and even a somewhat mystical sense of communication between the car and the driver. In scientific terms, it's about whether the vehicle's dynamic system can clearly communicate the state and limits of tire grip, allowing the driver to build confidence.
3. Stability: Maintaining Poise. As we begin to explore and push the limits of the vehicle's state, stability becomes increasingly important. It requires the car to maintain its intended trajectory under various conditions. This includes resisting crosswinds during high-speed straight-line driving, suppressing excessive body roll in corners, and ensuring the vehicle's posture can quickly recover during aggressive maneuvers like emergency obstacle avoidance to prevent loss of control.

These three vertices form a triangle because they are inherently contradictory in a physical sense. For example, a very soft suspension tuned for comfort will struggle to control body roll during high-speed cornering, thus sacrificing stability. Conversely, a very stiff suspension set up for track handling will provide clear road feedback on daily drives, failing to filter out small bumps and resulting in poor comfort. Therefore, the chassis design of any car is a trade-off within this triangle.

Specifically, a luxury sedan like a Rolls-Royce aims to maximize comfort, with stability as its foundation. As for handling, as long as it's smooth and effortless, there's no need to pursue a sense of "oneness" with the car. (After all, who cares about the hired driver's feelings?)

A supercar like a Ferrari leans completely to the other side. Its goal is to maximize handling, with stability as a safeguard. Comfort is the most expendable attribute because its target audience wants unfiltered road information, not to hold a conference call while on the track.

A high-performance sports car like the BMW M3 faces a more complex task. Since most of its buyers (the "poorer" ones, let's say) also use it as a daily driver, it needs to cover as much area within the triangle as possible. It must meet the owner's comfort needs for daily city commuting while also providing handling and stability for weekend track days or spirited drives. This is the most challenging and skill-intensive area of chassis engineering.

Chapter 2: The Engineer's Toolkit—From Strategic Layout to Tactical Execution

With the goals of chassis engineering defined, we can now look at the tools engineers have to achieve them. These tools can be broadly divided into two levels: the strategic level, which defines the source of the problem, and the tactical level, which solves specific problems.

2.1 The Strategic Level: The Art of Mass Distribution

The first and most decisive step in chassis engineering is the layout of the vehicle's heaviest components. This decision establishes a car's fundamental physical characteristics and determines the mechanical model that all subsequent tactical tools will have to deal with.

In ICE car design, engineers have considerable freedom in arranging the three most important components: the engine, transmission, and fuel tank. Their position, shape, and connection method collectively shape a car's basic character. This freedom of layout has given rise to several classic drivetrain formats in automotive history.

Front-engine, Rear-wheel drive (FR) is a classic example of seeking balance. In cars like the BMW 3 Series, the core design goal is to achieve an ideal 50:50 front-to-rear weight distribution. To this end, engineers move the engine as far back as possible, with its center of gravity behind the front axle, the transmission extending into the cabin floor, and even placing the battery in the trunk. This layout creates a clear division of labor: the front wheels handle steering, and the rear wheels handle propulsion. When the vehicle accelerates, the center of gravity shifts backward, further increasing the grip of the drive wheels. In corners, the load on the four wheels is relatively balanced, giving the vehicle's dynamic response a predictable, linear character. The driver can clearly feel the gradual transition from understeer to oversteer, resulting in a rich sense of communication and driving pleasure.

Mid-engine, Rear-wheel drive (MR) is the ultimate application of physical laws. Almost all supercars use this layout. Its sole purpose is to minimize the vehicle's rotational inertia. Similar to how a figure skater spins faster by pulling in their arms, a mid-engine layout places the heaviest components—the engine and transmission—as close to the vehicle's geometric center as possible. This minimizes the inertia that needs to be overcome when changing direction, resulting in unparalleled agility. Every steering input from the driver gets an immediate response, with almost no dynamic lag. Of course, this extreme agility also means a very narrow handling limit. Once control is lost, it's difficult to recover, placing the highest demands on driving skill.

Rear-engine, Rear-wheel drive (RR) is more of an engineering saga of defying destiny, with the Porsche 911 as its sole protagonist. From a physics perspective, hanging a heavy engine behind the rear axle is like attaching a giant pendulum to the rear of the car, constantly threatening its stability. Early 911s earned a reputation for being difficult to handle for this reason. However, Porsche engineers have spent over half a century battling this inherent physical flaw. Wider rear tires, intricately designed multi-link rear suspension, active suspension management systems, and even rear-wheel steering technology—all these engineering efforts had one goal: to tame that pendulum. Ultimately, they succeeded in turning this disadvantage into a unique advantage. The unparalleled rear-wheel traction provides astonishing acceleration out of corners, and during heavy braking, the rear-mounted engine acts like an anchor, stabilizing the car and giving it extremely stable and powerful braking performance.

These three distinct layouts clearly show that in the era of ICE cars, strategic layout choices were full of possibilities. It was an art of finding balance in freedom, highly dependent on the experience and intuition of engineers.

2.2 The Tactical Level: Four Core Control Tools

Once the strategic layout is set, engineers use a range of tactical tools to fine-tune the vehicle's dynamic performance. Four of these control methods are most important.

• Geometric Control: Systems like MacPherson struts, double wishbones, and multi-link suspensions are tasked with precisely controlling the wheel's trajectory relative to the body through a mechanical structure. Throughout suspension compression, extension, and body roll, this structure needs to manage key alignment parameters like camber and toe to ensure the tire always contacts the ground at the optimal angle, thus maximizing mechanical grip.
• Energy Management: This tool consists of two key components: springs (e.g., steel coil springs, air springs), which support the vehicle's weight and absorb large impacts, and dampers (shock absorbers), which control the spring's oscillations and the rate of energy release. Their job is to absorb and release impact energy from the road and suppress body vibrations. The spring's stiffness defines the suspension's basic hardness, while the damper's damping defines its resilience.
• Active Electronic Control: This layer uses electronic chips to monitor the vehicle's dynamics and road conditions in real-time and actively sends commands to the energy management layer (e.g., adjusting air spring pressure, changing the damping force of adaptive dampers). This transforms the chassis system from a passive mechanical structure into an intelligent system capable of active adaptation and intervention.
• Drive Force Control: This is a powerful tool often categorized under the powertrain. Its task is to use the vehicle's own driving force to actively influence its rotational dynamics. The most typical application is an all-wheel-drive system, especially one with torque vectoring. By sending more torque to the outer wheel in a corner or applying a slight braking force to the inner wheel, the system can generate a yaw moment that helps the car turn in, actively intervening in the vehicle's handling characteristics.

Chapter 3: The Challenges and Evolution of Two Paradigms

With the goals and technical means established, we can now place ICE cars and EVs into this framework to see the challenges they face and the methods they employ.

3.1 The Challenge for ICE Cars: Drive Force Limited by Mechanical Physics

Let's first look at ICE cars. The biggest ace up the sleeve of an ICE car engineer is strategic freedom. Like chess players, they can move the engine and transmission around to fundamentally change a car's character. If they want a balanced driver's car, they use FR. For an ultimate track machine, they use MR. If they're feeling bold and want to challenge the laws of physics, they use RR.

This strategic freedom allows ICE cars to have a very flexible orientation within the compromise triangle. But the other side of the coin is that once the strategy is chosen, ICE cars are somewhat constrained at the tactical level, especially with the drive force control tool.

Equipping an ICE car with all-wheel drive is not as simple as adding a motor. A transfer case, center differential, and driveshafts—this entire complex and heavy mechanical setup brings several problems: first, added weight, which is always bad news for handling (a key point we'll revisit); second, power loss and increased fuel consumption; and finally, cost. More importantly, the response speed of a mechanical system has inherent latency. The time it takes for a wheel to slip, the differential to lock, and power to be transferred to another wheel is orders of magnitude slower than an electric motor's response.

Therefore, ICE car chassis engineering is more of an art of creative strategic layout followed by meticulous refinement at the tactical levels of geometric control and energy management. Engineers spend countless hours on real roads, incrementally adjusting bushing hardness, anti-roll bar diameters, and damper settings to get infinitely closer to the theoretical optimum determined by the strategic layout. Drive force control is more of an expensive and cumbersome luxury. (Unless you're Audi, or Subaru, for that matter.)

The flip side of this meticulous craftsmanship is high cost and rigidity. Every minor adjustment to a damper's curve can involve lengthy negotiations with suppliers and rigorous testing. Changing an anti-roll bar's diameter means new molds and production runs. This reliance on physical components makes the tuning difficult to change once finalized. In stark contrast, an EV engineer wanting to adjust torque distribution or air suspension response speed often just needs to modify a few lines of code and push it to vehicles worldwide via an over-the-air (OTA) update. This is a fundamental difference in agility and even adaptability (a topic for another article).

3.2 The Challenge for EVs: Strategy Locked by the Laws of Physics

On the other hand, EV engineers face a completely different test.

Their strategic options are almost completely locked. The huge, heavy battery pack has no other place to go but flat on the chassis floor. To use the chess analogy again, the ICE car designer can move their major pieces freely at the start of the game, but the EV designer's queen is pinned to the center of the board from the very first move. This constraint gives EVs two seemingly contradictory starting characteristics.

On one hand, it's a gift. All EVs, whether they like it or not, get an extremely low center of gravity and a nearly perfect 50:50 weight distribution. This gives them a very high baseline for stability; they feel very planted even when driven casually.

But on the other hand, that gift comes with a curse—enormous absolute mass. Inertia is an inescapable law of physics. A 2.5-ton behemoth, no matter how low its center of gravity, cannot be made to feel agile in a corner.

So, the core conflict in EV chassis engineering becomes: with the strategy completely locked, how can tactical tools be used to counteract this massive physical inertia?

The EV engineer's answer is: wage an all-out, cost-is-no-object arms race at the tactical level.

• Upgraded Geometric Control: Double-wishbone and multi-link suspensions, often optional extras on ICE cars, are standard on EVs. The reason is simple: a traditional MacPherson strut's geometric flaws are magnified under the immense weight and simply can't handle it.
• Revolution in Energy Management: Air suspension and CDC adaptive dampers, once exclusive to luxury cars, are now mainstream in EVs. Only these intelligent systems that can actively and rapidly adjust stiffness and damping can hope to control the heavy body.
• Fine-grained Drive Force Control: This is another of the EV's trump cards. The complex mechanical all-wheel-drive system of an ICE car is replaced by simply adding another motor in an EV. More importantly, the response of electric AWD is on the millisecond scale, and the torque to each wheel can be controlled independently and precisely. When the vehicle is about to understeer, the system can instantly add 50 Nm of torque to the outer rear wheel while applying 20 Nm of regenerative braking to the inner rear wheel, creating a yaw moment that helps tuck the nose into the corner out of thin air. This torque vectoring is like a massive cheat code for chassis engineers. The suspension system no longer has to bear the full burden of handling. Its job is simplified, to some extent: just keep the tires on the ground, and let the drive force control do the math.

Conclusion: Two Philosophies, One Uphill Battle

At this point, I think I can answer the question that initially puzzled me: what is the connection between the leap in technology and the disconnect in experience?

The root of the answer lies in the two fundamentally different philosophies that ICE cars and EVs follow in chassis engineering.

The essence of ICE cars lies in strategic freedom and artistry. Their chassis philosophy is about shaping character. Engineers are free to shape the vehicle into any form—it can be an elegant and balanced FR, a nimble and lethal MR, or a rebellious RR. Each choice endows the vehicle with a unique soul, deeply embedded in its mechanical skeleton. All subsequent tactical tuning is aimed at bringing this inherent character to its fullest expression. Therefore, a great ICE performance car feels like an extension of the driver. You are communicating with a mechanical soul that has a distinct personality.

The reality of EVs lies in tactical extremity and science. Their chassis philosophy is about fighting nature. With the strategic layer locked down by the heavy battery, the natural tendency of all EVs is to be stable, not agile. Their strength comes from using overwhelming electronic technology and computing power to frantically compensate for, and even fight against, this innate physical flaw. Their handling is more of a real-time optimal solution calculated by code and algorithms in milliseconds.

This perfectly explains the contradiction. So, when people debate the handling of EVs, perhaps we can understand it this way:

• In terms of comfort, EVs are born straight-A students. A low center of gravity and a vibration-free motor give them an advantage in creating a quiet, smooth ride that ICE cars can hardly match.
• In terms of handling, EVs are born underachievers. Their massive inertia is their original sin. To defy their fate, engineers have no choice but to go for the most direct and effective method: brute force.

This "brute force" manifests in two ways: first, piling on hardware, using all the top-tier tactical tools like double-wishbones, air suspension, and active controls; second, overwhelming with power, using far more horsepower than ICE cars, combined with precise torque vectoring, to forcibly calculate a graceful cornering attitude.

So, technologies like BYD's DiSus are not just marketing buzzwords; they are real engineering achievements. But we need to understand their true mission: not to create an unprecedented level of driving pleasure, but to wage a grueling, uphill battle for a naturally cumbersome body. It allows a 2.5-ton sedan to post excellent lap times on a track, which is a testament to its powerful capabilities. But what the driver might feel in the process is not a dance with the vehicle, but rather witnessing a precise and cold war waged by countless sensors and actuators against the laws of physics.