What does RPM mean?

Well to put it simply, “Revolutions Per Minute”. The follow up question you’ll have is, “what’s revolving?”.

When your engine is running, the pistons travel up and down and rotate the crankshaft. The amount of full 360 degree rotations the crankshaft does in one minute. This tells you how the engine is operating at that exact moment. The more RPM’s, the more speed in that gear.

Why do you need an RPM gauge?

In the old days when you had to change gear manually, you needed to know how many revolutions the engine was doing to know when to change gear. Up or down, you had to know which gear to go into and where that was going to be in relation to the car’s power-band.

Even in a modern automatic transmission, it helps to know how many RPM’s the engine is doing. You can choose to change gear with the shifter, usually to the left or right. When going down a steep hill, you can use the gears to engine break and help stop overheating the brakes. It is imperative that you don’t over rev the engine, and also know how many more gears you can go down to slow down.

Also, it’s a gauge that moves and when it goes higher the car gets louder and faster, in and of itself it’s pretty cool.

How does an RPM gauge work?

It works in a variety of ways, but all send the signal to the gauge to tell you all the exciting, RPM based info you could need.

If you wonder why it’s 0 through 8 or 9 on the gauge, it’s because there’s a multiplier on the gauge. Usually x1000, so if it indicates that you’re at 4, your engine is doing 4000 revolutions per minute.

Some have a spinning wheel which when it passes by a sensor, transmits a magnetic signal to the sensor which travels to the gauge and displays the RPM at that moment. This used to work off of the distributor or camshaft gear, and the sender unit attached to the rotating object, the receiver being static and receiving the magnetic signal.

With most modern cars having the ECU controlling the ignition system, this sender and receiver goes to the gauge via the computer itself. The ECU controlling the ignition system means this is essential. It needs to know when to send the spark to ignite the air/fuel mixture.

If you have any problems with your RPM gauge, or any of your car’s auto electrics, click here and we can help solve those issues for you.