Saddle up

By ALASTAIR SLOANE

The adoption in New Zealand nearly 30 years ago of metric measurements has sanitised references to the power of engines.

Watts, kilo or otherwise, belong on lightbulbs or to power stations. Horsepower is the real thing. You can visualise it.

Besides, the reference honours the role of the horse, such as the Clydesdale, as a harnessed source of power.

Put roughly, an engine's power is determined by the energy needed to brake it, or the amount of pulling power used to stop the energy it develops. This is called brake horsepower, or bhp.

It is determined by a dynameter, an instrument used to measure expended energy.

For example, without putting too fine a point on it, the dynameter tells engineers that the engine they're bench-testing has the power of 100, 150 or 200 Clydesdales.

Torque is another ingredient. It indicates the amount of work the engine will do, while horsepower indicates the power available to do it.

Once upon a time a car's bhp was a rough guide to its top speed - 100 bhp meant it was good for 100 mph, 75 bhp for 70-odd mph and so on. But technology changed that.

So did going metric. The magic 100 mph became 160 km/h, which somehow sounded anaemic, and 100 bhp became 74kw (divide bhp by 1.36 to get kilowatts).

The 5.5-litre V8 engine in the Mercedes-Benz CLK 55 AMG develops 347 bhp, which means that it has the pulling power of 347 Clydesdales.

In metric-speak, the same motor develops 255kw, which could mean that it has the pulling power of two or three thousand lightbulbs. The only thing lightbulbs can pull is moths.

Sure, wiring up a few thousand lightbulbs would be easier than rounding up 347 Clydesdales, but horsepower is tangible. Just watch a team of Clydesdales at work at an agricultural show. They even sound strong.

Racing driver Owen Evans likes to talk in bhp. His turbocharged Porsche racing car develops 600 of it. One day he was testing the car at Pukekohe. The engine management system was playing up and the car was only putting out about 300 bhp.

"Come for a ride," he said. We blasted out of the pit lane and into the right-hander with Evans on the throttle and the car spluttering and coughing.

Suddenly, whatever was stopping the car developing full power cleared and 600 bhp kicked in.

Momentum is a funny thing. Being propelled forwards, at whatever speed, is the natural order of things. Going backwards is not. Going backwards in circles is not either, especially immediately after being fired forwards by 600 Clydesdales.

But Evans let the car take to the grass and spin itself out, all the while during the violence calmly looking over his shoulder to see where the rear was headed. We were soon back on the black stuff with 600 bhp on tap.

The spin sounded much better in the retelling when bhp was used. Six hundred Clydesdales sounds much better than 442 kilo thingies.

Same with the latest Mercedes-Benz, the CLK 55 AMG, and its throaty 347 bhp. Or the latest Daewoo, the facelifted 1.6-litre Nubira with 107 bhp (79kw) and the 2-litre with 133 bhp (98kw).

The CLK has enormous presence and is built by the performance arm of Mercedes-Benz. It costs a bundle - at $197,000 about eight times as much as the standard Nubira.

It has electronic anti-skid devices that can stop the careless driver from going backwards in circles. We tried them out the other day in the wet and they work.

They work on the racetrack, too, because the CLK AMG is the official Formula One safety car, the one that takes to the track if a race is interrupted.

It restarted the field at last year's Spanish Grand Prix, reaching 172 mph (280 km/h) before letting the racing cars have the track to themselves.

The Nubira doesn't go near a racetrack and it has no such anti-skid set-up. Once it starts going backwards in circles only the driver can catch it.

But going forwards it does the business, especially now that ride and handling have been improved and its steering is more precise.

The Nubira hatchback, sedan and wagon are priced between $25,000 and $30,000.