How The Mechanical Efficiency Of Cars Has Improved Over The Years

The classic car world is full of drivetrains that these days would be mouth-watering prospects. Take a Jensen Interceptor for example; it came with a 7.2-litre Chrysler V8 that produced a little over 300bhp. Nowadays, most manufacturers only need to work with 2.0 litres and some turbocharging to easily match that power output. These shortfalls from the past continue into almost every component on a car due to the rate at which technology develops. So what are the main factors that have affected the massive increase in efficiency of the modern car?

Fuel Injection Vs Carburetors

Fuel injection now dominates the process of fuel supply to a car’s engine where once the carburettor was the norm. The problem with carburettors was that they needed constant tuning to keep the engine running exactly as it should be. This inherently meant that engines with carburettors became less and less efficient over time where a fuel injected engine would be constantly monitoring the air/fuel ratio to maximise the engine’s performance.

Unless you went to a specialist or were a carb-tuning expert, the chances of finding the absolute maximum ratio from manually adjusting carburettors was a slight guessing game, making for either overly rich or lean engine settings. These days, an ECU is fully programmed to calculate and manage the entire fuelling system with little to no need for tinkering over the years. Carburettors also contain a bowl in which fuel sits and at idle this fuel begins to evaporate into the surroundings. This is another form of fuel wastage compared to fuel injection where the entire system is sealed.

Fuel Advances

The petrols used nowadays are described as unleaded due to the fact that up until 1996, leaded fuel could be used to power engines. The shift from leaded fuels was made because of its toxic nature to humans as well as a tendency to pre-ignite which can cause catastrophe for an engine. Lead fuels also affect engine efficiency due to the small amounts of lead residue that is left behind wherever the fuel contacts within the engine. Built up over time, this fine layer of deposit hinders piston movement and the combustion process, thus reducing the overall efficiency of the engine.

The potential octane levels within unleaded petrol is also higher than in leaded fuel as the developments in refinement have meant that octane levels can be increased without the existence of lead. This will result in a fuel that resists pre-ignition or detonation more effectively, creating more efficient combustion.

Many classic cars still running today must have a lead additive mixed in with the unleaded fuel from the pumps for their engines to function properly. If only supplied with unleaded fuel, the valve seats within the engine can suffer adverse wear if the lead residue is not present to shield them.

Materials Engineering

Engine blocks, gearboxes and differential housings all used to be predominantly manufactured using cast iron. Being a cheap metal that wasn’t affected much by warping when heated and cooled, the molten cast iron could be easily poured into moulds to mass produce large components.

Unfortunately, cast iron is much heavier than the alloys used today and isn’t as strong as the lighter steel and aluminium heads used in modern cars. This mass reduction not only helps performance but also vastly increases fuel efficiency and therefore the lighter metals have taken the place of the reliable but cumbersome cast iron.

Mass reduction is further enhanced by the massive influx of turbocharging in modern cars. Manufacturers no longer rely on a large-displacement engine for power, which inherently means that fewer and smaller cylinders will now do the job much more efficiently while minimising the weight of the powertrain.

Tyre Development

Tyres have evolved massively in the last few decades, with an endless choice of compounds and gradings available for whatever purpose you can come up with. Back before the world of winter tyres and run-flats, cross-ply tyres were the norm. The plys (the metal strands that make up the inner part of the tyre) criss-cross each other at a given angle to the direction of tyre rotation. It was only in the 70s that Michelin created the radial tyre which uses plys at ninety degrees to the direction of motion and is what we all have on our cars today.

One of the main advantages of modern radial tyres is the fact that they have flexible side walls whilst maintaining their strength. This allows for much greater control in the corners and avoids any steering wheel shimmying to get the car to where it needs to be. The radial tyre will retain its contact patch instead of rolling over into the sidewall mid-corner. This sharpness leads to much less disturbance between the contact patch of the tyre and the road surface, meaning the power transmitted from the engine can be applied more efficiently to the tarmac.

With technology in the car industry accelerating at an ever-increasing rate, it won’t be long until we will be looking back on the Ferrari 458 and Nissan GT-R and thinking how dated they have become. With electrification and automation on the forefront of manufacturers’ minds, the car’s efficiency will only ever increase as powertrains and transmissions are developed and revolutionised in the years to come. Give it twenty years and we’ll probably be scoffing at the horrendous efficiency of the internal combustion engine as an entity. Now isn’t that a scary thought…