Freight Factor: Payload-specific Fuel Efficiency

Traveling one-up in a semi-static sea of cars all headed to or from work in peak-hour traffic is practically a metaphor for envirogeddon. Not only is it the antithesis of enjoyable driving, it’s a profligate waste of energy. Some in the community are quick to point an accusatory finger at motorists, but the real blame in Australia rests with state governments, which have steadfastly, over decades, allowed public-transit infrastructure to grind practically to a halt. In the absence of a viable mass-transit system, there’s … driving. And everyone does it. With the end of oil at least foreseeable, and in the face of rampant global demand, something really should be done.

Odds-on (unless you endured more than the odd propeller-headed university physics course) you’ve never looked at fuel consumption quite like we’re about to now.

A great truth about fuel efficiency and consumption is frequently swept under the rug

tech, fuelJohn Cadogan17 September 2010 Comments

The Effect of Travelling Speed (Aerodynamic Drag) on Fuel Consumption

Air is thick stuff. Even a 10km/h headwind can play havoc with fuel consumption. Here’s why:

At 100km/h, aerodynamic drag accounts for about half the total resistance acting against the car’s forward progress. Battling into a 10km/h headwind is like driving into still air at 110km/h. But unfortunately the drag doesn’t go up by just 10 per cent. It’s more like 20 per cent, because drag varies with the square of speed. Twenty per cent of half the total resistance means 10 per cent higher fuel consumption.

(The maths:

tech, fuelJohn Cadogan17 September 2010Comment

Brake Mean Effective Pressure. Huh?

When it comes to engineering sleight of hand, two routines predominate for extracting more power on next season’s model. The first is simple: spin the old engine faster. If it can be forced to produce the same torque at higher revs, more power will result. (Power is a function only of torque produced and the revs at which it’s produced.) Unfortunately, this approach often compromises low-end driveability from greater overlap, etc.

Second trick is to add cubic capacity. Jumping from 2.0 to 2.5 litres means cramming 25 per cent more fuel/air mix into the process. If you’re lucky you’ll get 25 per cent more torque at the same revs for 25 per cent more power. Unfortunately, this option also adds weight.

In other words, a big engine spinning fast can be designed by dummies and yet produce copious power, whereas building a truly efficient, powerful engine (literally more bang for your buck-per-litre) needs a big R&D budget and smarter boffs

techJohn Cadogan17 September 2010Comment

What to do if You Are Stopped by the Cops

Your reactions at the roadside can make or break your case if you decide to go to court

When a police officer stops you at the roadside, some form of conversation inevitably ensues. However amicably this discussion proceeds, you must bear in mind that the ‘Law Vs You’ conversation cannot be merely a friendly chat. It is foremost an official police interview, and the officer’s first priority is to get you to admit the offence - to incriminate yourself. You are in a highly adversarial situation, but there is no requirement for you to help the police convict you. Strangely, many motorists do that anyway

John Cadogan17 September 2010Comment

What to do if you get a flat tyre

Prevention

Most flat tyres are preventable. Blowouts are caused by excessive flex in underinflated tyres. They overheat and let go, basically. Solution? Simple – check your tyre pressures every two weeks. The recommended pressure is on the car’s tyre placard, usually located inside one of the front door frames.

Location, Location, Location

Most flat tyres are unscripted – you don’t choose where or when they occur. Andrew Ticker, a technical specialist for Mercedes-Benz and veteran mechanic of 22 years says you should never attempt to change a flat tyre if you’re stopped close to the prevailing traffic flow. “Drive slowly [read: jogging pace] to an area where you can pull safely off to the side,” he advises. “Don’t worry about damaging the tyre – your safety is more important than that.”

Owner’s Manual

No, really. Check it out, if only to identify anything quirky about your car – such as whether your car has a space-saver spare tyre (these thinner spares are increasingly prevalent and often speed-limited to 80km/h.)

Standard Equipment

The standard toolkit usually boils down to a

safetyJohn Cadogan17 September 2010Comment