Diesel Engines Today’s diesel engines are becoming an ever more popular choice for the daily driver, this is due its ability to be more reliable, fuel efficient, durable, and overall more rugged. It is such factors as these which make diesel the appropriate choice for the driver who may be covering a high amount of mileage through their working year. One looked upon as a loud, sluggish and dirty technology, we are now witnessing the creation of a whole new image being applied to diesel engines, with improvements frequently appearing such as improved fuel efficiency, fuel flexibility and cleaner emissions it is becoming the drivers' number one choice of engine.  Unlike a petrol/gasoline engine, diesel differs primarily in the way the explosion occurs within the top of the compression stroke. Petrol engines start these explosions with the aid of spark plugs but diesel fuel removes this requirement thus igniting from the heat of compression. Significant improvements have been made mechanically in the way in which the mixing and injection steps are controlled, this was something that used to be controlled mechanically, which further lead to incomplete fuel combustion, fuel wastage and increased emissions. This has now been dramatically improved thanks to the introduction of direct fuel injection, which is controlled electronically by a communication module that takes in information from sensors such as engine speed, piston position, and coolant and oil temperatures. Thanks to this new technology fuel can now be burnt more efficiently, fewer emissions produced and more power delivered. Common Rail Technology Another system used to reduce exhaust emissions further and reduce engine noise output within today’s diesel vehicles is called common rail. The technology allows for the engine and injection system in question to be matched to each other in the best way possible.Such systems allow for the continuous image transformation of what diesel used to be to the now sporty fuel efficient and clean vehicle of today.  “Whereas in conventional diesel engines injection pressure is generated for each injector individually, a common rail engine stores the fuel under high pressure in a central container ("common rail") and delivers it to the individual injectors on demand. Benefits of common rail injection are reduced noise levels, stronger performance, improved emission control and greater efficiency.” Audi TDI Engine • Direct fuel injection • Forced induction – Turbocharged • Intercooler featured (Lower temp of compressed air from turbo, increases amount of fuel injected and combusted) • Volkswagen Group engine • Low displacement – Low surface area Honda HDi FAP • High pressure • Direct injection • 20% reduction in C02 emissions compared to indirect engines • 40% reduction in carbon monoxide, 50% in hydrocarbons and 60% in particles • (FAP) particles filter eliminates polluting soot particles • HDI engines able to take up to 30% of Biodiesel Honda CDTi engine • Common rail • Second generation • Turbo Injection  Diesel Disadvantages • Higher emissions caused by high combustion chamber temperatures • Expensive internal engine components due to high compression ratios • Fuel system components are expensive due to precise requirements • High maintenance and manufacturing costs | European Union Air pollutants in vehicle emissions include: • Carbon dioxide • Carbon monoxide • Fine particles • Nitrogen oxides • Unburnt hydrocarbons Pollutants should be restricted as such vehicle emissions can contribute to ill health, an increase in roadside pollution levels in built up urban areas and overall significant contribution to climate change.  “Following intense lobbying by the major car manufacturers, a compromise agreement was finally adopted in December 2008. The key elements of this are: • A gradual reduction in CO2 emissions from new vehicles to 120g/km for 65% of new cars in 2012. This will comprise a target of 130g/km to be reached by improvements in vehicle technology plus a 10g/km target to be achieved by complementary measures - better tyres, for example and the use of biofuels. • The 120g/km target will apply to 75% of new cars by 2013, 80% in 2014 and 100% in 2015. • Each manufacturer will be given a target based on the type of vehicles it sells. The heavier cars produced in Germany, for example, will have a higher g/km target.” The regulations and requirements listed above have been put in place by the EU and the industry associations representing the major car manufacturers Today we are able to use on board monitoring systems which use an ultraviolet optical based sensor to monitor a vehicles exhaust emissions. The system in question is able to simultaneously measure the concentrations of three of the major exhaust emission gases and output them to the vehicles on board computer. Such devices will aid significantly in monitoring any harmful pollutants produced form todays vehicles further aiding in controlling climate change. Other systems include the likes of physical sensors which can be held in place by an exhausts exit, whilst the vehicle is maintained at the RPM required within the manufacturer’s guidelines. Engine Management Systems Engine management systems or otherwise known as engine control units (ECU’s) or power control modules (PCM’s), are responsible for the successful management of a vehicle's powertrain. By successfully managing the powertrain it is able to monitor and control an engine’s ignition systems, fuel injection systems and emission controls. This is made possible by the wide variety of sensors and switches built in, sending information to the vehicles ECU system. Other areas controlled by the system include Air/Fuel ratio, ignition timing, idle speed, variable valve timing and electronic valve control.  On some of today’s latest vehicles we are also seeing the control of such areas as the transmission, system voltage regulation, ABS interaction and even sometimes interaction with (ATC) automatic temperature control modules. The constant development of emission restricting and safety assisting technologies within today’s new vehicles will make for a much greener and safer environment in which to live and commute. Lambda Sensors Fitted to today’s light commercial vehicles that are equipped with petrol engines, the lambda sensor or otherwise known as exhaust gas oxygen sensor, is located within the exhaust system and is responsible for monitoring the concentration of residual oxygen within the exhaust gases produced by the vehicle. The device works by measuring the three main toxic gases produced, these being carbon monoxide, oxides of nitrogen and hydrocarbons and then converting these into a less harmful gas. For this to be done the system employs an oxygen sensor and a three way catalytic converter which together are able to fulfil the task mentioned. Such devices are essential within the constant fight to reduce engine emissions and pollutants produced by internal combustion engines, Something of which is progressively becoming more and more vital within the automotive industry as the government enforce even stricter and tougher emission legislations.  |
