Everyone is Using Electric Assist, and You're Still Looking for Vacuum Tubes? Let Me Show You What the iBooster System Is 🚗⚡

Original: HonDa Magazine, Japanese Car Enthusiasts Magazine, 2025-03-15 10:38:24

Included in the topic: 📌 A Review of Japanese Car Technologies



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Technology is advancing rapidly 📈, changing not only our lives but also the cars we drive. Speaking of cars, the braking system is arguably the most important active safety system 🛑. However, in today's rapidly developing world, the reform of braking systems seems not as fast as other components. At least, the use of a hydraulic system for braking has not changed.



Nevertheless, although technology hasn't changed the fundamental form of braking systems, that doesn't mean there haven't been reforms to parts of the system, such as the brake master cylinder. 💡

This is the schematic of the entire braking system 🖼️. From the diagram, we can see that the entire braking system is essentially a hydraulic system 💧. Since liquids cannot be compressed, without assistance, the force from the driver's foot pressing the brake pedal is transmitted in a 1:1 ratio to the master cylinder, and then distributed to the four wheels through piping. Just imagine how much force you'd need to stop a one-ton car! 😱

For some older car models, when you open the hood, you'll see a round black object behind the brake master cylinder. Those familiar with car components likely know that this black object is a booster device. Its function is to amplify the force you apply on the brake pedal, making it feel as if just a light press can generate strong braking power 💪. This amplification device is called a vacuum booster. As the name implies, it uses vacuum from the engine to create a large pressure difference inside the booster, making it easier to press the brake pedal. This device is a truly great invention—it saves us a lot of effort 🙌. If you don't believe it, try pressing the brake pedal a few times after turning off the engine.

That black object is the vacuum booster ⚫, a device that uses vacuum to amplify the force from the driver's foot on the pedal. It is a passive auxiliary device.

This device has been around for a long time and has been used in all cars. However, it seems it is about to be replaced 🔄. Why do we say that? As mentioned before, the vacuum booster relies on engine vacuum. But what if there's no engine? Or what if the engine isn't running but the vehicle is still moving? These situations may not have occurred in the past, but now things are different 🌍. After all, electric vehicles are gradually becoming mainstream, and hybrids are also the main models of many manufacturers.

So what happens without vacuum? 🤔 Some manufacturers add an additional vacuum pump to supply vacuum for assistance. However, some others have opted for a different idea—completely abandoning vacuum assistance and using other forms of assistance, such as electric motors ⚙️. Hence, the iBooster system was created, first introduced by the famous German manufacturer Bosch 🇩🇪.

iBooster is a revolutionary booster device 🚀. It is installed on the brake master cylinder or can be considered part of the master cylinder. It uses an electronic control unit to control a motor, which then drives a three-stage gear set to achieve the same effect as vacuum assistance.

Of course, using a motor is not only for vehicles without vacuum; iBooster has its own advantages:
✅ Lighter than traditional vacuum booster systems
✅ Faster response time ⏱️
✅ Adjustable brake assist based on hydraulic pressure
✅ Compatible with modern driving assist systems (e.g., assisted braking, ACC cruise control) 🧠

This is the iBooster unit 🧩. It is essentially a brake master cylinder with an electric motor as the booster, reducing the weight of the system by eliminating the vacuum booster.

The iBooster's motor uses a three-stage gear set to achieve the force amplification effect. The motor itself can also independently build brake pressure and realize active braking, although this requires cooperation with assisted braking or ACC cruise control systems 🧰.

Why say this? First, we need to understand that a vacuum booster is a passive device—vacuum only plays an auxiliary amplifying role, and the driver still needs to actively press the pedal 🦶. Also, vacuum assistance cannot increase or decrease its effect based on actual conditions, so it cannot optimize braking force.

The iBooster, besides being passively triggered by the pedal, can also actively build pressure via its motor through an ECU, achieving active braking 💥. With assisted braking systems, when an emergency occurs, the ECU has already triggered braking earlier, hence it’s faster 🚨. Moreover, the ECU constantly monitors the braking situation, allowing the iBooster to adjust the braking force more precisely.

🔍 Reminder: Locking the wheels is not the best braking force—maximum braking occurs in the transition between rolling and sliding. That’s why ABS (Anti-lock Braking System) was invented.

This is the iBooster unit used in the CR-V. Although the shape is different, the structure is the same 🛠️.

Furthermore, the reason iBooster integrates better with assisted braking and ACC cruise control functions is due to its ability to independently build pressure.

Take ACC cruise control for example—it constantly monitors the speed of the vehicle ahead and adjusts acceleration or deceleration accordingly. Acceleration is managed via electronic throttle. But for deceleration, traditional master cylinders with vacuum boosters require the driver to press the pedal 👣. So they can’t fulfill cruise control braking. iBooster, using a motor to build pressure, enables automatic braking during cruise 🚗.

Previously, we introduced the fourth-generation MDX (YD4), which uses the iBooster system.

Actually, the iBooster system was originally developed to meet the needs of electric vehicles ⚡. However, due to its higher controllability, it can adjust brake assist levels via the motor—from comfort to sporty settings. More importantly, it significantly enhances braking performance 🏁.

Therefore, many non-hybrid and non-electric vehicles have also adopted this system. Honda, for example, uses iBooster in models such as the new CR-V, Accord, and the recently introduced new MDX—all of which use this electric assist braking system.