Driving Eco

The context.

2010-03-19T16:36:00.001-07:00

Driving Eco isn't meant to save the planet, but it might. It isn't meant to save you money, but it might. It is about knowledge and knowledge, as we all know, is power. Driving Eco is about having the knowledge in order to exercise choice.

So what is my idea of 'Driving Eco'? Well, in relation to driving my car its all about doing the same as I ever did but doing it using less energy. There is, of course, a story behind this and it is useful to give you a flavour.

Back in April of 2006 I was stopped twice by the Police for speeding related offences. I was very lucky to keep my license and the experience had a profound effect on me. 54 at the time, I realised that the more I drove the more likely, statistically, I was to be stopped. I'm also honest enough to admit that my attention isn't as good as it was 20 years ago so, as a result, and primarily to protect my license, I decided to observe a self imposed maximum speed of 60mph (observing lower limits wherever they applied).

It took a while, probably about a year, for me to settle into this new reality and the impact wasn't immediately apparent but I did notice that whereas I used to get about 440 miles to a tank, this figure started to creep upwards quite steadily. Early on it was 525 miles then it got up to 600. By this time I realised that something was happening and, as the new driving style evolved, the mileage per tank reached 700. I never managed to hit 800 but 725 was a regular distance. By my calculations, that's about a 60% increase at the cost of ............. almost nothing.

My journey times did extend but never more than 20% and my blood pressure certainly fell. I had more time to look at the scenery and passengers seemed to enjoy the experience. So it was a win - win - win - win and, along the way, I was doing exactly what I had done before but using 60% less energy. Amazing.

So this blogsite (thanks Blogger) is about doing what you did before but using less energy. Its that simple.

The fixed elements

2010-03-19T16:35:00.000-07:00

Driving Eco is an amalgam of elements, some are fixed (mainly the vehicle) and some are variable (mainly the driving style) so its best to have an idea of what you can expect from the vehicle. These expectations are going to be influenced, to a large part, by the vehicle you drive and its physical characteristics so lets look at the factors around vehicle design which influece its ability to be driven eco.

The two major aspects of a vehicle which affect its eco-ness are a) its weight and b) its frontal area. If your vehicle is 'heavy' then it will use more energy in acceleration and disippate more energy in deceleration. On the other hand, the lighter your vehicle is, the less energy it uses in acceleration and deceleration. And you can't change either of these characteristics.

Then there is frontal area. It takes energy to push the car through the air and the bigger the frontal area, the more power you need. Similarly, the faster you go, the more power you consume pushing the vehicle through the air. Conversely, the smaller the frontal area, the less power you need.

So, the ideal eco-car is a light vehicle with a small frontal area but practicality is always consideration. If you have three children and a dog, you can't expect a Nissan Micra or a Smart car to satisfy your requirements which means that, in making a car choice, you have to be selective within particular markets - town car or people carrier or multipurpose vehicle or Sport Utility Vehicle. The best 'eco' choice will be the lightest vehicle with the lowest frontal area in any paricular class.

Another 'fixed' factor is the cD or 'coefficient of drag' generated by any particular body shape and this describes how 'slippery' a shape is when it passes through the air. When viewed from the front, you can't change the maximum cross-section of the vehicle but you can shape the body to pass through the air with the least possible resistance.

The final fixed factor to consider is the tyre section or the width of the tyre where it rolls on the roadway. The wider the tyre the greater the aerodynamic drag and the greater the 'rolling resistance' the tyre generates.

The two images below summarise the extremes of these issues.

But you have probably already made your choice and bought your transport of choice or need so now we move onto the major variable - how you drive.

The variable - you

2010-03-19T15:23:00.000-07:00

There is a lot of 'physics' influencing the performance of your car and, to get the best from your car in eco terms, you need to find your way to the sweet spot in your own vehicle's performance. That means understanding the factors which limit eco-performance and, as much as possible, finding a compromise between them with which you can live.

The secret to 'Driving Eco' if there is one, is to drive smoothly with the minimum of power to get the job done. Accelerate with the throttle only just leading the engine. Short-shift to minimise the revs. Once at crusing speed, maintain it. Avoid braking because that wastes energy. Maintain a gap between yourself and the cars in front which will allow you to minimise speed loss when everyone else is getting on the brakes then on the throttle.

Experiment to find a satisfatory cruisng speed. Most cars have a sweet spot where the vehicle is maintaining a speed with what feels like the minimum of effort. Try and maintain the vehicle in that performance window.

Drive not for the car in front but for the furthest set of brake lights that you can see. Drive for the least strain and the maximum effect. Drive in order not to use the brakes but in order to maintain an even strain.

'Driving Eco' is about a decision to find the most efficient balance of the variables within your car's structure. You are the conductor and you must conduct the car in the most efficient manner possible. Anyone can drive inefficiently. That takes no skill whatsoever.