Fuel saving technologies: Part 1

Start/Stop

It is easy to think that start-stop technology was invented by BMW in the second half of the last decade. BMW refined and developed the technology but it actually originated in Japan in the mid-1970’s. With the recently increased emphasis on fuel saving and the reduction of CO2 emissions start/stop technology has again come to the fore, and is perhaps the most famous of the fuel saving technologies applied to cars running on internal combustion engines. Ford claims that its start/stop system improves fuel economy by roughly 4%, although this clearly depends on a number of factors.

How does it work?

The start/stop system automatically shuts the engine down when the car is stationary. This reduces the amount of time that the engine spends idling, reducing emissions and improving fuel consumption.

Manufacturers have developed the system so that functions such as the air conditioning system can remain operable even when the engine has shut down; this usually involves the use of an electric motor.

Who uses this technology?

Toyota was the first manufacturer to utilize the technology; they found that in heavy Tokyo traffic the Crown was 10% more efficient with the technology. Through the 1980’s and 1990’s there was sporadic use, mainly by the VW group which fitted it to the Polo Formel E, then the Golf Ecomatic in 1994 before fitting it to the Lupo 3L and Audi A2 3L in 1999. There was limited success in the early years, in part due to the high costs and drivers not being used to the engine cutting out, often finding it disconcerting.

In recent years, as legislation has demanded manufacturers implement efficiency measures, the technology has become prevalent, firstly in manual cars and then in automatic models. BMW, Audi and Mercedes all use the technology, even on their fastest models, such as the new BMW M5.

Brake energy regeneration

Recently BMW has claimed brake energy regeneration for its own; however it actually dates back to the late 1960’s. It can work with cars driven solely by an internal combustion engine, hybrid and electric cars, or in the form of a Kinetic Energy Recovery system, as seen in Formula 1.

How does it work?

Every time the brake pedal is pressed energy is wasted. The energy used to accelerate the car in the first place is turned into heat energy, which is not used for anything. This waste of energy is most obvious when watching brake lights flash on and off on the motorway where drivers follow too closely and do not plan ahead, this is dangerous, causes accidents and turns valuable fuel into useless heat.

Unlike traditional braking systems, which do nothing to harness the lost energy, regenerative braking systems try to harness the lost energy. BMW efficient dynamics uses this energy to recharge the car’s battery, therefore reducing the work the engine has to do to perform this function. However, hybrid vehicles have taken this further. In the case of the Toyota Prius, the majority of the braking duties are carried out by electric motors housed in the drive wheels, which become generators which supply energy to the batteries. These systems require no real servicing and even reduce brake pad/disc wear, but they do contribute to a very ‘wooden’ brake pedal feel which can be disconcerting.

The second type of brake energy regeneration is better known as KERS. It is well suited to sports cars as it uses a mixture of electrical and mechanical technology, using the brake energy to spin a flywheel at up to 80,000 rpm, which is then connected to the driven wheels when maximum power is required. This has clear benefits for performance cars and motorsport.

Tyres

Anyone who works with cars will tell you that tyres are important, they affect the dynamics of the car, the grip levels available and the efficiency with which the car rolls down the road. Tyres are also something that can be changed on any car, at any time meaning there is no need to spend tens of thousands of Euros on the latest Toyota Prius to make considerable gains.

The last decade has seen the major tyre manufacturers producing low-resistance tyres in large numbers. The European Commission estimates that the most efficient tyres can be as much as 10% more efficient than the least efficient.

Low rolling resistance tyres are constructed using silica which reduces resistance between the molecules within the tyre. This means that the tyre rolls along the road with less resistance, the only worry is that this could reduce the tyre’s ability to stop and turn the car too. In reality, the best examples of these tyres do those jobs very well, just do your research first.

Of course, you don’t need to replace all four tyres to improve the fuel efficiency of your car. It is also incredibly important to make sure your tyres are inflated properly. This usually means putting more air in them, due to tyres losing pressure gradually over time. Not only will this improve the fuel economy of the car, but it will also make the car handle better.