" SIR - We have fitted a Perkins Wolff high-speed diesel engine to the standard chassis of one of our staff cars and believe this is the first diesel-engined private car in this country. Such developments are a matter of interest to those who, like yourself, are responsible for keeping the general public informed of the modern trend."
Thus wrote the publicity manager of Alexander Duckham & Co to the editor of Practical Motorist in 1936, around the time that Audi first introduced their cars to the British market in the form of the so-called Audi Front, the name being derived from what was then an unusual feature - front-wheel drive.
To call it a 'modern trend' when diesels were undeniably noisy and slow and quite unsuited to cars was perhaps a little premature. Even forty years later, LJK Setright, a motor journalist of considerable repute, took the view that '...in private cars the merits of diesel engines are scarcely detectable.'
How things change. It may have taken the 'modern trend' nearly 70 years to catch up with the pre-war spin but now it's here I can tell you it has been well worth the wait. Anyone who has even looked at the latest V6 diesel-engined Audi A4 quattro must have an inkling that there is something special lurking under the bonnet.
To unleash its potential is quite simple. Position the tacho needle just above 1500 rpm, light the blue touch paper and watch the rest of mankind retire to a distant blob in your mirrors. Even in sixth gear at motorway speeds, safe overtakes are simply press 'n' go affairs as the torque-laden pistons do their stuff and the laws of physics are made to look sexy.
Even studying the engine specification on paper does little to prepare you for what I rate as being one of the most rewarding driving experiences in some 25 years as a motor journalist. Not only was the engine smooth and powerful, it delivered top-drawer performance with barely a murmur. Apart from an attenuated but tell-tale detonation knock on tickover, audible mainly from outside the car, the engine note was more felt than heard and at 70 mph in top gear the only detectable sound was from the hefty tyres wrapped round the optional 17-inch wheels. Except in the rain, when the wipers contribute a rather laboured 'swish', which seems peculiar to VAG cars.
Leonard Setright's article of 1976 went on to point out that '..the essentially heavyweight diesel engine is also essentially feeble, and with safety regulations forcing cars to get heavier anyway, there is little attraction in the idea of making them even heavier, and, at the same time, denying them the power necessary to move their increased weight at a reasonable rate.'
In those days, reasonable meant reaching 60 mph in under 20 seconds. For example, the diesel Granada, with its 2.2-litre naturally aspirated Peugeot engine, took 27.2 seconds to reach 60 mph, en-route to a modest 83 mph, flat out. That engine developed 90 lbs/ft of torque and 63 bhp. Compare it with the Audi power unit, which develops 274 lbs/ft of torque (way above a Land Rover) and 180 bhp. The torque has quadrupled and the power increased three-fold.
Part of that is down to the presence of a turbo, but a large chunk can be attributed to advances in material technology combined with even greater advances in engine management systems. Modern materials make for lighter yet stronger engines and allow the use of much higher injection pressures. Modern electronics allow pin-point timing and very precise measures of fuel to maintain optimum efficiency. Add these to the variable turbine geometry of the Audi turbo unit and you have a recipe for huge gains in power and torque.
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