Have you ever seen one of those videos of a Tesla drag racing a purpose build racer? I have, and it got me thinking, just how do these cars pull off such incredible 0-60 acceleration speeds? So, I did some research and here’s what I found.
In principle, it’s down to a couple of factors, however, it can be attributed to one main one, torque. Electric cars have the ability to provide lots of it. Fast. They can provide torque at a much lower RPM than conventional gasoline-powered vehicles. Let’s explore what that means and the other factors which influence this impressive event.
The AC Motor – a Brief History
Back in the late 19th century, Nikola Tesla spearheaded the development of what he considered to be the superior type of motor, the AC motor. At the time, the DC motor was being developed by Thomas Edison, who was in strict rivalry with Tesla, even going out of his way to create an electric chair with AC current to show how dangerous it was.
Fortunately, Tesla succeeded and the motors that drive our appliances in out homes, offices and factories all use motors based off his design. Naturally, electric cars are no exception, using these type of motors to deliver the rapid acceleration that has become characteristic of them.
Before we get into the root cause of such accelerations, it’s important to understand some background as to the mechanics of AC motors.
How Does It Work?
Take a look at the picture above, you can see blue and red coils on the motor, they are wired in series, but in opposite directions. Here’s how it works:
As the electromagnet coils are supplied with AC, they produce magnetic fields. Since AC current comes in the form of a sine wave, the movement of the rotor is smooth. Additionally, when the red coils are at peak activity, the blue coils are at zero activity, since the AC current is opposite for each.
Furthermore, the magnetic fields produced by the coils create an induced potential current on the rotor in the centre. Since the current in the rotor produces it’s own magnetic field, it opposes the magnetic field that the coils produce, exerting a force on the rotor. Finally, since the current keeps changing between the coils, the rotor continually spins in one direction.
Impressive! Considering Tesla created this concept in the late 19th century anyway! So, the motor drives the wheels and that leads us on nicely to the torque/speed graph of such motor.
The Torque / Speed Graph
It all comes down to this one graph, the torque/speed graph. As you can see, right from the very start, the AC motor has almost 50% of its maximum torque at very little speed. As the car accelerates, the torque increases to the point where it is at its maximum, which is about 60-80 mph, depending on the motor.
Suddenly, the torque curve drops off dramatically, but don’t let that mislead you. Since the torque decreases, there is a decrease in acceleration so the car accelerates slower from 60-100 mph than from 0-60 mph.
On the graph above, there is a section labelled the stable region and from what I have found, that is because the motor is fairly stable, not accelerating or decelerating too much. Based on that, the unstable region must get its name from the large increase in torque.
Why Are Internal Combustion Engines so Much Slower?
Above is the torque/speed graph for a conventional vehicle. Evidently, torque comes much later and is nowhere near instant. In fact, if you do some basic predictions, it has barely any torque at around zero revs.
Consequently, the starter motor was invented, with one very important purpose. Its job is to rotate (or crank) an internal combustion engine. Then as the revolutions increase, it can provide its own torque to get the car moving.
These little motors run off the car’s battery, hence why a car won’t start if the battery is flat. Alternatively, if you have ever seen anyone pushing their car down the hill, that probably means they are jump starting it. Simply put, jumpstarting cranks the engine so the starter motor is not needed.
How Do They Compare in a Drag Race?
Armed with that knowledge, here’s how they stack up against each other in a drag race. I’m comparing cars of similar speeds and price ranges.
In a race from 0 to 60 mph, there’s an obvious winner, the electric car. The instant torque pushes past the slow to start gasoline car. We’re at the pinnacle of gasoline acceleration and I can’t see it going below 2 seconds 0-60 time, purely because they are limited by torque at low RPM.
Here, it depends on the cars and the drivers, but you would expect the electric car to win. Its superior instant torque gives it a decent time advantage by the time it hits 60 mph. Though the gasoline car is likely to start accelerating faster after that, it’s a bit late.
Now it gets interesting! Shortly after both cars reach 100 mph, it is likely that the conventional car will likely pull ahead of the electric car. Recall that on the electric car torque curve, the torque dropped off after a bit, moreover, the gasoline car curve shows torque increase where the electric car decreases.
So, the conventional car pulls away and takes the half mile. Obviously, anything greater than a half mile will allow the gasoline car to claim victory.
How Far Can We Push Electric Car Acceleration?
We’re reaching the end of the road for internal combustion engine acceleration, so it’s time to move onto something new. Could we be seeing 0-60 mph acceleration in the electric cars of the future? Perhaps.
Chances are you’ve heard of the Tesla Roadster. When it was announced way back in 2017, Tesla claimed it had a real world 1.9 seconds 0-60 mph time. That’s incredible and is a decent chunk faster than any other car on the road today.
That thing will be incredible in drag races and might beat a conventional gasoline car in a half mile race. Wouldn’t that be incredible! We’re now only a year away from seeing the fastest accelerating production car of all time.
Conclusion – Does This Even Matter?
Thanks to speed limits on the road, electric cars are victorious here. There are many scenarios which they present their superiority:
For example, you’ve probably been in a situation where you’re trying to pull out of a junction and there’s a car coming. It’s a risky pull-out, however, you could be waiting a while if you don’t go now. Fortunately, electricity is on your side, with the fast 0-60 mph acceleration, you can reach the speed limit in a matter of seconds, leaving that conventional car in a pile of dust.
Simple road maneuvers are made easier with electric technology, including overtaking, and the pure enjoyment of blistering acceleration. That’s the nature of electricity and we take it for granted everyday in our cars, smartphones and well, pretty much everything in our homes.
After all, when your phone is on standby and you turn it on, the screen is on within a few milliseconds. You don’t have to wait for it to ‘warm up’ or ‘get ready’ to illuminate the screen.