All cars come with multiple dials on its dashboard. While most of us are familiar with the fuel gauge and the speedometer, there is that one other dial that’s a bit more complicated – the tachometer or RPM gauge. So, what exactly is a tachometer? By definition: It is an instrument which measures the working speed of an engine, typically in revolutions per minute (RPM). In short, it helps inform us how fast the engine is turning and rotating. The tachometer aims to read the rotation of the engine’s crankshaft and it also lets you know when to shift.
These days, cars with automatic transmissions are slowly discontinuing tachometers, but they are an absolute necessity in manual models to let drivers know when there is a problem with the transmission as well as precisely when to shift.
What is ‘redlining’?
You will also notice that compared to a speedometer, the RPM gauge displays smaller numbers such as 1-8, with red lines on the higher digits. These red lines are the danger zones for your engine. When you fail to shift to a higher gear, the needle moves to the red line. If your tachometer reaches these red levels, it can cause overheating and excessive wear on the engine. But although some believe this will cause your engine to explode, all modern cars incorporate a fuel cut-off that will stop an engine from reaching the point where it could cause permanent damage, typically just past the redline itself. The tachometer is just a way to tell you that your engine has reached its maximum RPMs. The best way to avoid this is by shifting gears within the range of your engine’s maximum performance whenever possible.
What happens if you redline?
The red lines are there for a reason; but if you do accidentally end up in the red for a fleeting instant, you have little to worry about as long as you don’t do it again. You could also book a check-up for your car if you’re worried.
Most cars these days have a rev-limiter built-in and prevent you from redlining by setting up the system to cut off the fuel flow to the engine, or to disable the ignition system until the engine falls to a safer speed. The safest bet, however, is to avoid over-speeding the engine and not upshifting the gear.