4 main reasons why a tachometer is important for car performance

Usually only seen in manual transmission vehicles, the tachometer is important for data collection, gear shifting, fuel economy, and engine life.

Modern cars, trucks and SUVs are becoming more dependent on technology every year. From driver-assisted safety systems to advanced fuel system monitoring and adjustment software, today's daily driver is very different from those of the past. One of the remaining elements (usually on vehicles with manual gear shifting) is the tachometer. In years past, a "tachometer" was used by the driver to determine the best and most efficient time to shift from a lower to a higher gear. Today, the visual tachometer isn't as important as it was in years past, but it serves a purpose.

Understanding the actual purpose of a tachometer

Contrary to popular belief, a tachometer is more than just a gauge that displays engine speed. In fact, the tachometer consists of a system of control equipment that collects data, transmits it to the ECU (engine control unit) and affects the operation of several independent systems. Officially, a tachometer is a device that measures the rotation of the engine's crankshaft, which is responsible for the rotation of each connecting rod and piston in the combustion cycle. When the crankshaft rotates 360 degrees, it completes a complete revolution. The total speed of rotation of the crankshaft is measured in revolutions per minute or rpm.

The RPM is displayed on a gauge, usually located on the driver's dashboard and, in most cases, on the left side. It usually shows a series of numbers from zero to 8 or 9 with several lines between each integer on an analog or digital display. An integer between 0 and 9 is actually defined as 1,000 times that number. The last digits displayed on the tachometer are usually highlighted in red. When the engine is accelerating, the arrow will point to a number equal to the engine rpm. When the arrow points to a red mark, it is considered a "redline" or works above the recommended.

Knowing the function of the tachometer, let's look at 4 main reasons why it is important for the operation of the car.

1. Captures and transmits data to help switch your car

If you have an automatic transmission and have a tachometer, you will notice some consistency when shifting from a lower gear to a higher gear. The transmission is programmed to upshift at a given engine speed. RPM is measured by the tachometer and relayed to the TCM (Transmission Control Module) or ECU. The same revolutions are displayed on the gauge. While the scale itself is purely for display purposes, it lets the driver know when to expect a shift.

2. Let manual transmission drivers know when to shift

The tachometer sensor also helps the driver know when to change each gear when operating a manual transmission. Most cars, trucks, and SUVs with manual shifting should shift from down to up when the tachometer reads between 3,000 and 4,000 engine rpm. Drivers are usually taught to shift the engine based on the sound and driving conditions rather than the revs of the tachometer, but the tachometer serves an important function by providing a visual indicator.

3. Helps Improve Fuel Efficiency

A working tachometer can also help those with a manual transmission improve their fuel economy. Most car manufacturers specify in the car's owner's manual at what RPM the engine should be shifted for optimum efficiency. To achieve optimum efficiency, a modern internal combustion engine is combined with a particular type of transmission or transmission and drive axle ratio. The combination of all three separate systems is known as a power train. Manufacturer-recommended shifting helps transfer power to the wheels with minimal drag. With reduced "load" or "drag" on the engine, less fuel is burned, resulting in better fuel economy.

4. Extends engine life.

An internal combustion engine contains several moving parts that require lubrication to operate. As each part moves, friction is created with each revolution of the engine, and in turn, heat. The faster the engine spins (or the higher the RPM), the more heat will be generated. When this happens, the metal parts in contact eventually heat up until they begin to lose lubricity, which can lead to catastrophic failure. When the tachometer and ancillary components are working properly, the transmission can shift on time, or manual transmission drivers can shift as recommended, extending engine life.

The tachometer plays a vital role in a modern engine as it goes much further than just a moving needle on a gauge. If you notice that the tachometer sensor is not working, it could be a sign of a minor problem, such as a broken sensor or loose wire, or a potentially serious problem, such as a damaged time sensor. If you suspect that the tachometer is not working on your vehicle, contact a professional mechanic and have them diagnose the cause of the problem so proper repairs can be made.