What Is a Car Governor In a Car?

A governor or speed limiter prevents a vehicle from accelerating faster than a programmed threshold. Cars sold in the US have speed governors that have been installed by the manufacturer. How do they work? What are governors for? Do they help enforce speed limits? Read on to find out.

How Does a Speed Governor Work?

Speed governors for cars track speed with the help of a speed sensor. There are also speed governors that prevent an engine’s RPM from exceeding a certain speed. Once a vehicle reaches or exceeds its programmed top speed, it’ll communicate with the vehicle’s powertrain control module, which cuts off air and fuel flow to the engine. This prevents the vehicle from accelerating further even when the driver might have his foot planted on the throttle.

There are different speed governors: one that prevents the rpm from going high, and another that prevents the vehicle from going over a certain speed.

–Anthony Harlin, ASE Certified Master Automobile Technician

Many governors are only programmed to stop vehicles from exceeding speeds that are as high as 155 miles per hour (mph). However, some brands like Volvo have announced that it’s lowering its vehicles’ top speed to 112 mph.

Why Do Speed Governors Exist?

Manufacturers install speed governors to make driving safer. It prevents drivers from reaching speeds where the vehicle becomes unpredictable to drive. At high speeds, the air is moving so fast that it makes the vehicle feel unstable, similar to how a kite can wobble as it flies through the air. Aside from stability, most vehicles aren’t built to turn and corner at high speeds. An inexperienced driver turning suddenly at high speed can easily turn the car into a skid. Aside from losing control, some vehicle components aren’t built to handle the stress of high speeds. This can be the reason why a Ford Mustang with a V6 has a governor that limits it to 113 mph. Meanwhile, the V8 version has a governor that limits it to 150 mph.

Vehicle tires also have a speed rating on their sides indicating the fastest that you can run them in before they’re at risk of blowing out. The world’s fastest car, the Bugatti Chiron, has specially-designed tires with carbon fiber that can handle its 300 mph top speed, with each set costing $42,000.

What Are the Types of Speed Governors?

Several types of speed governors can monitor and enforce a vehicle’s speed.

Mechanical Centrifugal Governor

A mechanical governor uses weighted balls that are mounted to a lever arm. These balls rise upwards as they’re spun by the engine. If the engine spins too fast, the governor’s lever arms rise to a certain threshold. Once the vehicle reaches its max speed, the governor will prevent the throttle valve from opening further. This design was typically used in the first vehicles with speed governors.

Vacuum or Pneumatic Governor

This type of governor relies on the air pressure generated by the engine flywheel’s cooling fins. As the vehicle speeds up, the flywheel creates air pressure that controls a diaphragm in the governor’s housing. This is connected to the fuel control linkage, which controls fuel flow depending on the amount of air pressure generated by the flywheel. As the vehicle reaches high speeds, it’ll generate enough air pressure to cut off fuel flow.

Electronic Governor

Electronic governors rely on a magnetic pickup or the vehicle’s speed sensors to determine a vehicle’s current speed. Once it reaches a threshold, the governor’s controller will activate a stepper motor connected to the engine throttle that modulates airflow to control the vehicle’s speed.

Can Speed Governors Enforce Speed Limits?

Considering 85 mph is the fastest speed limit in the country, you might be wondering why governors only kick in far beyond the acceptable speed limit. If governors exist and are installed in most modern vehicles, why do they allow drivers to drive at dangerous speeds?

The US government doesn’t rely on in-vehicle technology to enforce speed limits. Instead, the country generally relies on law enforcement.

Speed governors aren’t installed by manufacturers to enforce speed limits. The responsibility is on police and highway patrol to constantly monitor vehicle speed limits and behavior on public roads, especially interstates and major highways. Speed cameras also allow for more consistent enforcement. But these systems can’t monitor all roads and prevent drivers from flooring it. Aside from that, Americans don’t want to lose their right to go fast.

In a survey of 1,000 drivers, 68% of respondents said that they didn’t want a speed limiter lowering their vehicle’s top speed. Only 14% of respondents believed that speed limiters should be required by law. In a different survey, almost half of Americans admitted that they drove at least 15 mph over the speed limit in the past 30 days.

At the end of the day, it’s your responsibility to always drive within speed limits and keep safe on the road regardless of the presence of a governor in your vehicle.