Most people rarely give the act of starting their car a moment’s thought until something goes wrong. However, those first few moments after your engine has come to life can reveal a lot about its present health and may influence how long it will survive.
Your RPM should be around 1000 when you start a car, although the level will quickly settle down to the values specified in the automobile’s manual. This rapid rise in RPM helps warm your engine oil temperature, which leads to better lubrication and less friction.
So, let’s discuss RPM and what it means when you start your vehicle. I’ll discuss why your RPM might be higher in specific vehicles and help you understand when a higher RPM is a cause for concern. So, let’s get into it!
RPM is an abbreviation for revolutions per minute. It indicates how fast a machine is operating at that moment. When discussing automobiles, RPM tells you how many times your crankshaft makes one complete rotation in a minute.
The higher your RPM, the faster your engine is running.
If your car has a tachometer, you’ll be able to get an RPM reading the moment you start the vehicle. In older cars, you can usually find the tachometer to the left of the speedometer. This round gauge will list numbers ranging from 0 to 8 (or, sometimes, 0 to 10) and often has a red line near the higher numbers.
In newer cars with digital displays, the tachometer may appear in various places or may not even exist at all. If you own a car without a tachometer, you’ll need to judge your engine speed by how your engine sounds. Engines running too fast generally make a roaring or revving sound.
Assuming you don’t own a car with a high-performance engine, let’s go back to the moment you start the vehicle and pretend that it is a frigid morning. As you shiver behind the steering wheel, you decide to press down the accelerator a few times, hoping to generate some cabin heat.
Your engine roars, and your RPMs spike. You notice your tachometer’s needle cross the red line once or twice. Have you seriously damaged your engine?
Modern engines can handle short periods of high RPM use. You’ll encounter these periods whenever you accelerate quickly, like passing on an interstate highway. You are more likely to damage your engine when you rev your engine frequently or for extended periods.
You are more likely to put your engine through these extended periods of abuse with certain transmissions. Manual transmissions or dual-clutch transmission systems driven in full manual mode give you the most chance to keep RPMs high.
These transmissions generally have fewer technological safeguards against redlining. Many newer cars with manual transmissions now have rev limiters which will help prevent extended visits to the RPM danger zone and expensive visits to your mechanic.
Before we go much further in our exploration of RPMs and engine speed, I should take a moment to explain why high-performance racing engines can survive, making that roaring sound a lot longer than your average commuter car.
Racing engines are for durability at high speeds. They achieve high horsepower through a combination of torque and engine RPM. These high-performance engines are designed to keep piston speed lower than your average engine, thus reducing stress on the connecting rods and crankshaft.
The use of lightweight metal alloys, stiffer valve springs, larger pistons, and other modifications allow a racing engine to survive frequent periods of high revving that would severely damage the engine of most average cars.
Modern automatic transmissions usually shift into the next highest gear as they approach the higher RPM levels tolerated by your engine.
In addition to this protection, some cars will shut down the spark or the fuel injectors when you have hit your highest possible gear and your RPMs are above the red line. These systems will cause your car to decelerate until the RPMs drop to a safe level.
These safeguards do not make it impossible to destroy an automatic transmission vehicle’s engine with a dedicated revving session. It just means you need an extra degree of stupidity to do so. It’s so simple. Anyone can do it.
Put your car in park or neutral and mash the accelerator pedal down. Keep it to the floor for a while with the engine running. Listen to that engine roar! If you have a tachometer, you can watch your RPMs climb into the red line zone and, perhaps, even max out for a little while before you experience catastrophic engine failure. It is not the least expensive way to have a few minutes of fun.
Over-revving can damage your engine. Catastrophic engine damage from over-revving an automobile engine comes in various ways. Many of these engine failures are fatal. Those that you can repair tend to be quite expensive.
So, let’s take a closer look at what happens when you over-rev your engine:
Connecting rods connect your engine’s pistons to the crankshaft. Each connecting rod is a solid piece of metal. The pistons and cylinders of the machine are above them. The crankshaft is below them.
When a connecting rod dislodges at high speed in a revving engine, there is no good place it can go. It will damage anything in its path, causing a chain reaction of part failures which will turn your engine into junk in about a second.
Throwing a connecting rod is the most common cause of catastrophic engine failure in gasoline-powered car engines.
Unlike high-performance engines, the engines in most cars have soft valve springs. When you rev your engine, these springs tend to float. In most cases, your engine suffers no harm, and you never even know the floating occurred. That’s the good news.
The bad news is that whenever you float a valve, you run the risk of a piston head colliding with a valve. You’ll know something is wrong almost immediately as you’ll hear a loud knocking sound coming from your engine, particularly at high speeds.
The damage from these collisions can range from bent valves to damaged piston heads. In financial terms, the damage goes from costly to incredibly expensive.
Sustained high revving creates high heat and friction within your engine. Although your clutch relies on friction to function, too much heat and friction will cause the tension between your clutch plate and flywheel to increase to unhealthy levels. You’ll not only wear out your clutch faster, but you’re also risking severe flywheel damage.
The increased heat generated from constant and sustained high revving can lead to oil breakdown. This breakdown could lead to the early deterioration of some essential engine parts.
These parts include:
- Piston Rings
- Cylinder Walls
- Main Bearings
- Rod Bearings
- Piston Cylinder Set Pins
As you can see, a high revving habit comes with a high cost.
Revving your engine early and often is rarely a good idea. Revving a cold engine, however, can cause considerable damage over time.
Even with today’s technological safeguards, you risk long-term damage to vital engine components by increasing friction before adequately lubricating. When starting your car, a light foot and an abundance of caution will help keep both your engine and your bank account healthier for years to come.