Toyota understanding what sets them apart
Engines: understanding what sets them apart
When you’re looking for a car, it’s easy enough to tell which car you like the look of, which car has a touchscreen display, which one is safest and many of the other features that differentiate one car from another. But how do you compare engines, other than engine capacity?
Here are a few pointers to head you in the right direction:
Petrol or diesel?
While they are both refined from mineral oil, petrol and diesel fuels have different characteristics. Diesel has approximately 15% more energy per volume than petrol, mainly because it is denser than petrol.
This, combined with the combustion process, means that a diesel engine is more economical on fuel than a petrol engine that produces the same amount of power (kiloWatts or kW) and torque (Newton metres or Nm). To achieve this, though, almost all modern diesel engines are fitted with a turbocharger, to maximise the efficiency of this patent power.
For example, a Toyota Hilux Double Cab fitted with the 2.7-litre VVTi petrol engine produces 122kW and 245Nm, using 10.7L/100km to do so. The same vehicle fitted with the 2.4 GD-6 diesel engine produces 110kW and 400Nm, using 7.4L/100km. If we do some maths, we find out that the diesel produces 10% less power (kW) than the petrol engine and 63% more torque (Nm), and yet uses 30% less fuel to do so.
Petrol cars are usually cheaper to buy than diesel cars, because diesel engines invariably have a turbocharger (and not all petrol engines do), and diesel engines need to be stronger due to the high compression ratio they have, so require more actual metal to make the engine stronger.
Turbocharged or naturally aspirated?
A turbocharger, often shortened to ‘turbo’, helps a car’s engine to breathe by forcing air into the combustion chamber. It’s that simple. And by helping the engine to breathe, it speeds up combustion and produces more power. Naturally aspirated engines are those without a turbocharger. Turbocharged vehicles often have a ‘T’ in their model badge, like 1.2T.
For example, a Toyota Starlet has a 1.4-litre petrol engine that produces 68kW of power and 130Nm of torque. A Toyota C-HR has a 1.2-litre turbocharged petrol engine that produces 85kW of power and 180Nm of torque. So, despite having a smaller engine capacity, the C-HR’s engine is more powerful and produces more torque.
In terms of fuel consumption, though, the Starlet comes out ahead, using a claimed average of 5.4 litres of petrol per 100km as opposed to the C-HR’s 6.3 litres per 100km.
When buying, you will see that turbocharged engines, even in the same range of vehicle, are more expensive than naturally aspirated engines. Critics would also say that turbocharged engines require more maintenance than ‘normal’ engines, and potentially higher maintenance costs.
How many cylinders do you want?
In basic terms, a cylinder is the tube in which a piston goes up and down, to produce power. Engines with a small total capacity, like 1-litre, are often three-cylinder or four-cylinder units. Most engines in the range between 1.2-litre and 2.8-litre are four-cylinder engines. When engines are bigger than that, from 3-litre and up, they are often six-cylinder or even eight-cylinder.
The smaller, three- and four-cylinder engines are usually what is known as ‘inline’ engines, which means that the cylinders are all in a line.
The bigger engines with six or eight cylinders are often in a ‘V’ configuration, with an equal number of cylinders on each branch of the ‘V’.
There is no real advantage in the number of cylinders: in the small capacity engines, the power and torque as well as the fuel economy is comparable between three- and four-cylinder engines. They do feel a bit different, though, and three-cylinder engines are usually slightly off-beat and rougher (in a good way). Inline engines are smoother and cheaper to make, but take up more space in the car.
At the other end of the scale, the V-configuration engines are often more expensive to make but are more compact and take up less space in the engine compartment. V6 engines are less smooth than an inline six-cylinder engine due to the odd-number of cylinders on each side of the V, but many drivers love the sensation of a V6 under acceleration. Toyota vehicles with V6 engines include the 4.0 V6 petrol Hilux and Fortuner, while there are also V8 engines in the Land Cruiser range.
So far we’ve been talking about petrol and diesel engines, but there is another option if neither of these ticks all the boxes – a hybrid. A hybrid car uses electric power to assist a small-capacity petrol engine. In the Toyota Prius, for example, a 1.8-litre petrol engine is assisted by electric power to reduce emissions and improve fuel economy, and add power and torque. The electric motor adds 53kW to the overall power and is powered by batteries that are recharged as the Prius drives and brakes. This results in a claimed average fuel consumption of a remarkable 3.7L per 100km and emissions of 87g of CO2/km.