The Diesel Engine
A German engineer, Rudolf Diesel(1858-1913) invented an engine which would
run on a more easily-produced alternative fuel than highly volatile petrol.
Also, having less moving parts and not having any ignition, made it cheaper
to produce, longer lasting and easier to waterproof. It also produced a lot
more torque at low engine speeds(rpm) but at the expense of much less
horsepower(bhp). The optimum efficiency of any engine is at the speed(rpm)
where it produces its maximum torque preferably at low engine speeds. This
made the diesel engine most useful in situations where the engine could be
run at a constant speed, i.e., generators, ships engines, farm tractors, etc.
On top of this, an engine running at a constant low speed gives very good
fuel consumption so it sounded too good to be true!
Well it is too good to be true because to produce more acceptable and
comparable power outputs as the petrol engine, the diesel needs to be nearly
twice the capacity of the petrol engine. Even then it probably needs a
turbo-charger to produce comparable performance and consequently loses most of
it's better fuel consumption figures.
The biggest problem with the diesel engine is the disastrous effect
it has on our environment caused by the exhaust gases. Diesel fumes which,
although not being fatal, are the cause of all the breathing problems.
This is because the exhaust particulates are so small that they cannot
be filtered and they can be absorbed into the blood stream via the lungs.
There are no catalytic converters for diesel engines! Medical advice to
anyone who find themself in heavy traffic with lots of diesel fumes is to
close all windows and vents and if your are a pedestrian or on a
bicycle, find an alternative route!
Hauliers and bus operators, demanding vehicle longevity, chose diesel
engines and with an open road and long distances to cover, it made some
sense but as traffic levels have mushroomed, so have the exhaust fumes as
they sit stationary or stop-start and chug their way through traffic jams.
Then some misguided car manufacturers produced diesel-engined vehicles for
fleet operators adding to the problems and some of the public still believe
that there are benefits from the diesel engine. Even the Government have
admitted their mistake by putting the tax back up on diesel fuel!
Diesel fuel - ah yes, that horribly smelly stuff that gets everywhere
and probably contributes to some of the many accidents on our roads today.
You can always see spilt diesel when it's raining because of the shiny,
bluish patch on the road. This combined with rubber from the tyres makes
an extremely slippery surface especially if you are on two wheels! Petrol
on the other hand, while being a derivative of oil, is not oily and will
evaporate.
However, the petrol engine is not the complete solution as the carbon
monoxide from a petrol engine can kill you. However, it can only do this in
confined spaces and being unstable, it will eventually turn into carbon dioxide.
Catalytic converters speed up the process of making the exhaust from petrol
engines much cleaner however they do convert the sulphur impurities into
hydrogen sulphide which is also an irritant. The only good point being that
the anti-knock lead additive has already been removed as this contributed to
the poor development of childrens' brains - we've now got TV and computer games
to thank for that!
Recent development of the petrol engine has put it way ahead of the
diesel engine and at the same time, made it equally reliable and long-lasting.
Petrol engines can now easily achieve 50miles per gallon(mpg) and more as
well as being capable of covering 200,000miles without a rebuild. Also, the
new hybrid cars which use a very small engine for assistance or to charge
batteries, can achieve as much as 80mpg and they do not use a diesel
engine!
A Which? survey found that the once-accepted benefits of
buying a diesel-powered car, i.e., greater fuel economy and resale value, are
no longer true. The higher cost of diesel fuel outweighs the slight gain in
fuel economy and as diesel vehicles are now much more complicated than the
early models, servicing costs are no longer cheaper than for a petrol-engined
vehicle. Also, recent cost comparisons reckon that the owner of a diesel-engined
vehicle would have to travel over 40,000miles in a year to make it an economically-viable
option to a petrol-engined vehicle.
So why do people buy a diesel-powered vehicle? Or even worse, a turbo-charged
diesel-engined 4x4 - a tractor in disguise! They like the rattling sound that
can't be shut out unless you use one foot thick insulation. They like the smell
of diesel fuel that inevitably gets onto the carpets and permeates throughout
the whole vehicle. They enjoy continually stirring the gearbox every time a
slight hill confronts them or they want to gain some sort of speed whilst
ignoring the black haze that trails behind them. They are probably vegetarians
and probably recycle everything whilst believing that they are saving the
planet - what hypocrites!
These, of course, are my personal views about the diesel engine.
D. F. Galle
Links: