These are often an eclectic mix of styles, shapes, engines and indeed purpose. However, over the past month the road test team and I have noted that we’ve been driving an abnormal number of diesel vehicles. You’ll detect that all the recent road tests are oil burners. In light of this, I’ve decided to explore the diesel engine, from its inception to the current cutting-edge, where the former tractor propulsion now wins Le Mans.
As you might have guessed, the brainchild of diesel engines was named Rudolf Diesel, a 19th Century man who had a dream of creating an engine that didn’t waste heat during the combustion process. Through trial and error, and even a near-death experience, he refined the ‘hot-bulb’ design by Herbert Akroyd Stuart and Richard Hornsby, into a high compression diesel engine. The diesel engine then took over from steam power; we saw more trucks on the road and a steady decline of the railway network.
The diesel engine was mainly used in industrial applications with the most car-like machine seen with an oil burner being a tractor besides of course a large truck. In terms of diesel-powered vehicles it wasn’t until halfway through the 20th Century that we saw really commercially viable Mercedes-Benz and Volkswagen diesel vehicles in the mainstream. The problem with these vehicles was that they were naturally aspirated, making them slow and smokey. However, the consumption benefits of the diesel motor could not be ignored and Mercedes-Benz and Volkswagen stuck with it, when others stopped.
Manufacturers then began fitting magical turbochargers to these engines, which overcame the power problem, while still allowing for the efficiency. I remember the first turbodiesel BMW that I drove was a 325tds; it was nothing like the remarkable motors that we have today but was a sort of predecessor showing that diesels didn’t have to be incredibly slow.
Then, at the turn of the 21st Century the USA and Europe became big on environmental regulations, which forced manufacturers to create cleaner, more efficient diesel motors. There are three aspects that one needs to inspect when it comes to clean diesel. The first being low sulphur diesel; locally our diesel cars have run on 500ppm (500 parts per million of sulphur content) for years, however, 50ppm and even 10ppm are available and recommended for the more modern diesel engines.
The second aspect is in the engine itself, which employs high pressure injectors, a strengthened engine block and better manufacturing techniques, which lead to less loss of heat and more efficient use of fuel. The third aspect of the modern diesel engine is in the exhaust, where catalytic converters and post-combustion filters trap particulate and NOx matter and prevent these harmful particulates from being emitted into our air.
Recently, diesel engines have been getting a bad rap in the press after the Volkswagen emissions saga, but from my experience with diesel motors they can provide the type of performance that we need on a daily basis while using very little fuel to do so. There is an argument to be made about how bad those emissions from a diesel vehicle are for us. Nonetheless, in a country like ours, where there are no restrictions on emissions - besides a government money-making scheme like emissions tax on new cars - I still see the diesel remaining very relevant.
Mr Diesel would be proud that the operation of his engine design has remained roughly the same for over 100 years, with engineers refining it to a point where we have diesels in motorsport, diesels in off-roading, diesels for efficiency and the traditional workhorse diesels, all chugging along, doing their thing.
