4x4 Economy - Fuel Saving

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4x4 Economy - Fuel Saving - The Environment

All motorists use fuel and hence contribute to pollution and global warming, so what can we do about it?

Over the past few months 4x4web has been contacted several times by press, TV and radio for its views on 4x4's and the environment. This is a subject that is important to everybody and not just to the environmentalists.

I hope by this web page to perhaps bring a new slant on a subject that has been well aired. I have looked at this in 2 ways. Firstly the usual way, and then in my own way.

All the usual stuff (still very important)

• Have your vehicle regularly services according to manufacturers recomendations. An intune engine is better than an out of tune engine in both fuel economy and reduced pollution.
• Tyres should be correctly inflated for the circumstances.
• Speed should be within the speed limits.
• Avoid areas of known congestion if possible.
• Accelerate gently, anticipate and read the road ahead.
• Plan your journey in advance. Can that school run be combined with the shopping trip. Can you share school or work runs with other drivers.

A Scientific sideways look at fuel economy

Fuel use is tied up with Force and Energy

f=ma
Force = Mass x Acceleration

To get to the top of a hill we must increase our potential energy.

e = mgh
Potential energy = mass x acceleration due to gravity x height.

Aerodynamic Drag
D = ½ρv²C_dA

When we brake we have to loose Kinetic Energy

KE = ½:mv²

You will see that m or v appears in all the above. Lets see how we can cut our fuel use/pollution production.

The Force Equation f=ma

The mass of the vehicle. For simplicity we will regard mass and weight as similar. By reducing the mass we reduce the force and hence fuel used. Note that Mass in the above formulae is not raised to a power so doubling the mass doubles the force needed, and halving the mass halves the force needed to achieve a given acceleration.

Potential Energy e=mgh

Here again we have mass not raised to a power. So a 10% decrease in mass reduces by 10% the potential energy that needs to be gained to get to the top of a hill.

Drag (aerodynamic) Equation

D = ½ρv²C_dA

What can we effect here. The Coefficient of drag is mainly as a result of the design as is the cross sectional area A. However we can affect both of these if we have a roofrack fitted. A roofrack will both increase the C_d and increase the A (plus also add a bit of m although that dosn't come into thie equation). However the biggy is v or v² as it actually is. This is a squared relationship so increasing speed from say 60 mph to 75 mph increases the contribution from 60x60=3600 to 75x75=5625. ie a 25% increase in speed produces a 56% increase in drag. Even 70 mph to 75 mph, a 7% increase in speed produces a 14% increase in drag.

So what can we do????

Answer... Think fuel economy. This does not need to be at an extreme level just think about it.

• We all know "Speed Kills" but speed also has a significant effect on fuel consumption. Both too slow and too fast wastes fuel. Sitting in a traffic jam every day wastes time and fuel. Both are precious. Driving at 80mph down the motorway is wasting fuel and breaking the law.

Nigel Leak

To be continued.....

What do cooling towers at a power station do?????

Answer provide global warming.