How Speed Limiters Work

Why limit how fast a car can go? Believe it or not, there are more reasons to do this than to let a car run as fast as it possibly can.

The primary reason is safety. Obviously, the roadways would be a lot more dangerous if everyone was driving well over 100 mph (160.9 km/h) all the time. The faster a car travels, the more aerodynamically unstable it is due to wind resistance, so it's hard to handle. Most drivers simply don't have the reflexes it takes to handle those kinds of speeds.

Speed limiters are also there to protect the engine and the car itself. An engine's lifespan drops significantly if it's running at maximum speed all the time because it is being made to work much harder than it normally would.

Another important factor is the car's tires. Ever look at all those numbers and letters on the sides of your tires? Those tell you not only the size of the tires but also their speed rating. The speed rating tells you the maximum velocity a tire can sustain before it's in danger of blowing out. Most family sedans and vans have S- or T-rated tires, meaning it's best to keep them under 112 mph (180.2 km/h) and 118 mph (189.9 km/h), respectively. Some exotic sports cars have Y-rated tires, which can handle up to 186 mph (299.3 km/h) [source: Tire Rack].

There are environmental factors as well. The faster a car goes, the more fuel it consumes and the more pollution it produces. In addition, law enforcement in your area probably wouldn't be too thrilled if you decided to attempt to best the Veyron's speed record.

Okay, so we've seen that speed limiters are a good thing. But what if you really want to throw caution to the wind and simply go as fast as you can? If that's the case, there are a few ways around speed limiters. Next, we'll take a look at how it's possible to disable a speed limiter.

To make a long story short, yes, there are ways to disable your car's speed limiter. Like most computers, the functions of your car's engine computer can be modified. But that's not always easy to pull off.

Believe it or not, some cars have built-in ways to defeat the governor. On the Nissan GT-R, the car itself automatically raises its top speed when its GPS system detects that you've brought it to a racetrack. And going back to our previous example, the new Ford Mustang has a programmable top speed so parents can restrict how fast their teen drivers can potentially go [source: Ford].

Okay, that's all well and good, but how do you actually turn off a speed limiter? Many cars now offer aftermarket performance chips or engine computer reprogramming that alter the way the engine performs. These modifications can add power or fuel economy to an engine, depending on what the tuner desires. That programming can also include removing the speed limiter.

There are even ways to do this mechanically. For example, if you own an older Nissan 240SX sports coupe, disconnecting two sensors in the transmission will make it so the engine computer no longer knows the engine RPMs in fourth or fifth gears, so the limiter never kicks in [source: 240SX.org].

Every car is different and a little Internet research can show you how to do it on your own vehicle— but keep in mind that it might not always be the safest thing to do. Also, make sure your tires and your driving skills are up to the task first.

In Germany, there are stretches of the Autobahn where there are no speed limits. This is why a lot of high-end European cars are very comfortable at high speeds, and often have much higher top speeds than cars built in other parts of the world. While this article did get me thinking about disabling the speed limiter on my own car, I don't think I'll do it. There are very few places in North America where you can sustain speeds of 130 mph (209.2 km/h) or more— at least, not without getting arrested. But maybe I'd do it if I knew a trip to the Autobahn was in order.

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