Let’s Torque ICE and EV Physics

June 21st, 2022

Comments Feed

As technology improves with each passing year, the inside mechanicals of an internal combustion engine (ICE) have become more refined, stronger, lighter, and more efficient at harnessing power from the combustion process and feeding it out to the wheels.  Adding Hybrid technology to the ICE has also enabled car manufacturers to make greater gains in power and efficiency.  Hybrid engines are designed to try and use electric power from the electric motor(s) instead of fossil fuel power from the ICE for as much of the commute as possible.  When required, the ICE takes over the power delivery when electric power has been drained, or electric and ICE can work together for enhanced power on acceleration.  Purely electric vehicles (EVs) don’t have combustion energy but can still produce phenomenal levels of power and torque.

If you’ve ever taken the slightest look at any car review in a magazine or online, or even browsed through a car brochure, somewhere in the read you’ll come across some of the main bits on the engine stats and specs. Some of the specs are easy enough to understand – like the 0–100 km/h time measured in seconds, which is a measurement of the quickest time it takes the car to go from a standstill to 100 km/h.  100 km/h is equivalent to 62.14 mph, so if you are presented with an Imperial measurement looking at the 0–60 mph sprint (USA reviewers use this), it’s roughly the same as the usual nought-to-the-ton metric figure.

However, some specs are a bit harder to get a handle on – like power output.  Power is described as the rate at which work is done, or else the rate at which energy is converted into motion.  In cars and vehicles of all types, the formula for calculating power is relatively complicated (or kind of).  The power output of an engine is measured in kW (kilowatts) using metrics, which is the force times the velocity: power = work/time = (force x distance)/time.

All sorts of things go into delivering the power and torque created from an ICE out to the road, such as the number of cams (pistons) in the engine, the number of combustion chambers in the engine, the flywheels, the gear set, the tyres, and even the size of the combustion chambers.  The reason why EVs can make power and torque quickly and efficiently is that they do away with all the internal mechanical workings of an ICE (the ICE motor) and use magnetism instead of combustion for making power and torque available to the driveline.

Yes, power actually used to be measured in horsepower, which was originally used to compare how well a steam engine or traction engine could work in comparison to a big Clydesdale horse (hp).  Here’s some stats for you:

1 kW equals 1.34 hp

1 kW equals 737.56 foot pounds per second

1 hp = 550 foot-pounds per second (ft lb/s)

1 hp = 0.75 kW

As you may already know, power is closely related to torque.  Torque is a measure of the force that can cause an object to rotate about its axis point.  The whole set-up with a vehicle’s engine, transmission, and drivetrain involves rotational motion, so where the rubber finally hits the road is where the final delivery of the torque from the vehicle’s engine and mechanical components are then converted back to straight-line motion, where and when the rubber applies a force to the road.

Torque is measured in Newton meters (Nm).  Newton metres are the metric units used for torque.  The non-metric unit used for American cars is in pound-force per feet, also known as pound-feet. Just to be confusing, pound-feet is also used for torque, while foot-pounds are used for power, something that’s likely to drive you half dotty. However, the formula for conversion is 1 pound-foot = 1.356 Nm.

An ICE engine loses a lot of its initial combustion power and torque as this gets delivered mechanically to the rubber on the road, where all the action happens.  All the weight and friction of the moving ICE powerplant components drain the power and torque levels before what’s left of it is delivered to the wheels, the rubber on the road used for motion.

Hybrid vehicles (those that combine electric and ICE motors) can use electric motors to boost ICE power and torque output, thus improving fuel efficiency and power and torque delivery.  EVs can deliver so much more power and torque to the rubber on the road because they haven’t got all the extra weight and friction of the ICE’s mechanical componentry.  EV motors don’t need all of this to create a big enough force for motion.