A wise old man told me the other day that small cars had no use for a tachometer and that most drivers had no idea whatsoever about how to use the legendary dial in the dashboard.
That last thing he may be right about, but the first one I totally disagree with. It’s not the size of the car that determines how suitable a tachometer is, but how it’s used. I belong to those who like the presence of the eager needle in my dashboard. It reinforces the feeling of having a real, mechanical connection with the car – whether I’m on a long trip or playing around on a sunny Sunday. A parallel can be drawn with the old-fashioned amplifiers in a decent stereo system. These should have large illuminated VU meters on the front, not necessarily to much effect, but cool to watch as the music plays from the speakers.
The wise man came with several words of wisdom about the tachometer: “Such an instrument also takes some concentration away from the road when trying to decipher the meaning of the needle’s position on the dial. It doesn’t tell you anything all that important, certainly not more than the road ahead does! You have to learn to listen to the engine instead – it tells the most secrets ”. Here he is right. Most of us who have been driving for a long time quickly find out the characteristics of an engine just by listening to its sound.
A tachometer simply shows the number of turns that an engine crankshaft (the rotating part which converts the piston’s up and down movements of the conrods into circular motion) per minute. Typically, engines have a useful operating range between 800 (idle) and 6,000 rpm. Some sports cars can rev up to 9000 rpm or even higher.
The first tachometer is considered by many to have been developed by German engineer Dietrich Uhlhorn in 1817. Uhlhorn needed a meter to measure the speed of a machine. His simple need and the solution he came up with would become a standard accessory on vehicles of all kinds over the next 200 years. In 1840, a tachometer was used to measure the engine speed of a vehicle – on a locomotive, to be precise. Although the first gasoline-powered car was developed in 1886 by Karl Benz, it’s unclear when the first car included a tachometer.
The dial of a tachometer usually has a red line in the higher numbers, indicating where the engine (not the car) reaches the manufacturer’s recommended maximum revolutions. If you cross the line and move into the “red zone”, life becomes exciting and entirely at your own risk. The reason for the restriction is that pistons, valves and valve springs can no longer follow each other and a collision between them will cause engine failure. As a general rule, it is unnecessary to operate the engine in this red range for more than a second, if at all. That being said, many newer cars have a built-in ‘rev limiter’ which electronically prevents the engine from exceeding the limit by immediately switching off the power until the engine speed is lowered.
If you think about it, the rev counter is not much use in regular daily driving, but nevertheless, we don’t want to do without it. It can – for example – be helpful in choosing the appropriate speed and gear setting for a particular situation. Or for getting to know your car better by getting some simple information, such as how many revolutions per minute your engine is doing at 100 km / h. Most of this can be done with the ears, but the rev counter gives the facts in dry numbers.
Whether enthusiastic drivers really use the tachometer while driving to keep an eye on engine revs, or just their ears, I don’t know exactly, but at 120 km / h you are actually moving at 33 meters per second, so is there enough time to linger on the needle in the dial anyway?
What’s your opinion on tachometers and their usefulness in a car, dear ViaRETRO reader?