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The paper discusses the concept, design and final results from the ‘Ultra Boost for Economy’ collaborative project, which was part-funded by the Technology Strategy Board, the UK's innovation agency. The project comprised industry- and academia-wide expertise to demonstrate that it is possible to reduce engine capacity by 60% and still achieve the torque curve of a modern, large-capacity naturally-aspirated engine, while encompassing the attributes necessary to employ such a concept in premium vehicles. In addition to achieving the torque curve of the Jaguar Land Rover naturally-aspirated 5.0 litre V8 engine (which included generating 25 bar BMEP at 1000 rpm), the main project target was to show that such a downsized engine could, in itself, provide a major proportion of a route towards a 35% reduction in vehicle tailpipe CO2 on the New European Drive Cycle, together with some vehicle-based modifications and the assumption of stop-start technology being used instead of hybridization.

In the present study, Large Eddy Simulations (LES) have been performed with a 3D model of a step nozzle injector, using n-pentane as the injected fluid, a representative of the high-volatility components in gasoline. The influence of fuel temperature and injection pressure were investigated in conditions that shed light on engine cold-start, a phenomenon prevalent in a number of combustion applications, albeit not extensively studied. The test cases provide an impression of the in-nozzle phase change and the near-nozzle spray structure across different cavitation regimes. Results for the 20oC fuel temperature case (supercavitating regime) depict the formation of a continuous cavitation region that extends to the nozzle outlet. Collapse-induced pressure wave dynamics near the outlet cause a transient entrainment of air from the discharge chamber towards the nozzle.

Throttling loss of downsized gasoline engines is significantly smaller than that of naturally aspirated counterparts. However, even the extremely downsized gasoline engine can still suffer a relatively large throttling loss when operating under part load conditions. Various de-throttling concepts have been proposed recently, such as using a FGT or VGT turbine on the intake as a de-throttling mechanism or applying valve throttling to control the charge airflow. Although they all can adjust the mass air flow without a throttle in regular use, an extra component or complicated control strategies have to be adopted. This paper will, for the first time, propose a de-throttling concept in a twin-charged gasoline engine with minimum modification of the existing system. The research engine model which this paper is based on is a 60% downsized 2.0L four cylinder gasoline demonstrator engine with both a supercharger and turbocharger on the intake.

Precise, repeatable and representative testing is a key tool for developing and demonstrating automotive fuel and lubricant products. This paper reports on the first findings of a project that aims to determine the requirements for highly repeatable test methods to measure very small differences in fuel economy and powertrain performance. This will be underpinned by identifying and quantifying the variations inherent to this specific test vehicle, both on-road and on Chassis Dynamometer (CD), that create a barrier to improved testing methods. In this initial work, a comparison was made between on-road driving, the New European Drive Cycle (NEDC) and World harmonized Light-duty Test Cycle (WLTC) cycles to understand the behavior of various vehicle systems along with the discrepancies that can arise owing to the particular conditions of the standard test cycles.

The octane appetite of an engine is frequently characterised by the so-called K value. It is usually assumed that K is dependent only on the thermodynamic conditions in the engine when knock occurs. In this work we test this hypothesis: further analysis was conducted on experimental results from SAE 2019-01-0035 in which a matrix of fuels was tested in a single cylinder engine. The fuels consisted of a relatively small number of components, thereby simplifying the analysis of the chemical kinetic proprieties. Through dividing the original fuel matrix into subsets, it was possible to explore the variation of K value with fuel properties. It was found that K value tends to increase slightly with RON. The explanation for this finding is that higher RON leads to advanced ignition timing (i.e. closer to MBT conditions) and advanced ignition timing results in faster combustion because of the higher pressures and temperatures reached in the thermodynamic trajectory.

Carbonaceous deposits can accumulate on various surfaces of the internal combustion engine and affect its performance. The porous nature of these deposits means that they act like a “sponge”, adsorbing fuel components and changing both the composition and the amount of fuel in the combustion chamber. Here we use a previously developed and validated model of engine deposits to predict adsorption of normal heptane, isooctane, toluene and their mixtures in deposits of different origin within a port fuel injected spark ignition engine (Combustion Chamber Deposits, or CCDs, and Intake Valve Deposits, or IVDs) and under different conditions. We explore the influence of molecular structure of adsorbing species, composition of the bulk mixture and temperature on the uptake and selectivity behaviour of the deposits. While deposits generally show high capacity toward all three components, we observe that selectivity behaviour is a more subtle and complex property.

Deposits forming in the injector nozzle holes of modern diesel cars can reduce and disrupt the fuel injected into the combustion chamber, causing reduced or less efficient combustion, resulting in power loss and increased fuel consumption. A study of the factors affecting injector nozzle tip temperature, a parameter critical to nozzle deposit formation, has been conducted in a Peugeot DW10 passenger car bench engine, as used in the industry standard CEC F-098 injector nozzle deposit test, [1]. The findings of the bench engine study were applied in the development of a Chassis Dynamometer (CD) based vehicle test method using Euro 5 compliant vehicles. The developed test method was refined to tune the conditions as far as practicable towards a realistic driving pattern whilst maintaining sufficient deposit forming tendency to enable test duration to be limited to a reasonable period.

Modern diesel passenger car technology continues to develop rapidly in response to demanding emissions, performance, refinement, cost and fuel efficiency requirements. This has included the implementation of high pressure common rail fuel systems employing high precision injectors with complex injection strategies, higher hydraulic efficiency injector nozzles and in some cases <100µm nozzle hole diameters. With the trend towards lower diameter diesel injector nozzle holes and reduced cleaning through cavitation with higher hydraulic efficiency nozzles, it is increasingly important to focus on understanding the mechanism of diesel injector nozzle deposit formation and growth. In this study such deposits were analysed by cross-sectioning the diesel injector along the length of the nozzle hole enabling in-depth analysis of deposit morphology and composition change from the inlet to the outlet, using state-of-the-art electron microscopy techniques.

A series of viscous and surface friction modifier additives has been studied in a modified SI engine with separable valve train lubrication. From the results, it has been possible to classify the hydrodynamic or boundary lubrication nature of the observed effects for a series of lubricant additives. It is shown that the frictional benefit of a given additive depends not only on the engine operating condition but also on the engine components on which it is acting. For some additives a fuel economy benefit can switch to a disbenefit as operating regime changes and a different aspect of the additive properties becomes important. Such observations are rationalised in the context of conventional lubrication theory.

Spray characteristics of injectors depend on, among other factors, not only the level of turbulence upstream of the nozzle plate, but also on whether cavitation arises. "Bulk" cavitation, by which we mean cavitation which arises far from walls and thus far from streamline curvature associated with salient points on a wall, has not been investigated thoroughly experimentally and moreover it is quite challenging to predict by means of computational fluid dynamics. Information about the effect of the injector geometry on the formation of bulk cavitation and quantitative measurements of the flow field that promotes this phenomenon in gasoline injectors does not exist and this forms the background to this work. Evolution of bulk cavitation was visualized in two gasoline multi-hole injectors by means of a fast camera.

The present investigation is centered around two motored research gasoline direct-injection engines, equipped with a pressure-swirl atomizer closely spaced with the centrally located spark plug. At first a Laser Doppler Velocimetry system was employed to characterize the in-cylinder airflow in one of the engines. A comparison was made to velocity profiles in a port-fuel injected engine of similar design characteristics, which revealed a different decay mechanism of the large-scale flow structure and associated higher turbulence levels in the pentroof of the cylinder. Second, images of the hollow cone fuel spray generated by the direct injector were recorded for three different injection timings in order to discuss the temporal and spatial development of the liquid phase in the engine cylinder in terms of its interaction with the gas motion.

A European test procedure for evaluating engine deposits, using the Mercedes Benz M111 bench engine, has already been approved for inlet valve deposits (IVD) and is under development for combustion chamber deposits (CCD) by the Co-ordinating European Council (CEC). This paper describes CCD effects on emissions using a slightly modified version of this engine test procedure and compares it with CCD/emissions data from road vehicles. The engine used was a modern four valve, four cylinder, 2.0 litre passenger car unit and the bench test procedure used extended the operating time from the specified 60 hours to 180 hours. The road vehicle trial used two Mercedes Benz C200 passenger cars fitted with the M111 engine and two Ford Mondeo 2.0 litre passenger cars. Data was collected up to 11200km, approximately equivalent to 180 hours operation of the bench engine.

The effects of lubricant oil and fuel properties on low speed pre-ignition (LSPI) occurrence in boosted S.I. engines were experimentally evaluated with multi-cylinder engine and de-correlated oil and fuel matrices. Further, the auto-ignitability of fuel spray droplets and evaporated homogeneous fuel/oil mixtures were evaluated in a combustion bomb and pressure differential scanning calorimetry (PDSC) tests to analyze the fundamental ignition process. The work investigated the effect of engine conditions, fuel volatility and various lubricant additives on LSPI occurrence. The results support the validity of aspects of the LSPI mechanism hypothesis based on the phenomenon of droplets of lubricant oil/fuel mixture (caused by adhesion of fuel spray on the liner wall) flying into the chamber and autoigniting before spark ignition.

It is anticipated that worldwide energy demand will approximately double by 2050, whilst at the same time, CO2 emissions need to be halved. Therefore, there is increasing pressure to improve the efficiency of all machines, with great focus on improving the fuel efficiency of passenger cars. The use of downsized, boosted, gasoline engines, can lead to exceptional fuel economy, and on a well-to-wheels basis, can give similar CO2 emissions to electric vehicles (depending, of course, on how the electricity is generated). In this paper, the development of a low weight concept car is reported. The car is equipped with a three-cylinder 0.66 litre gasoline engine, and has achieved over 100 miles per imperial gallon, in real world driving conditions.

Engine stop/start and cylinder deactivation are increasingly in use to improve fuel consumption of internal combustion engine in passenger cars. The stop/start technology switches off the engine to whenever the vehicle is at a stand-still, typically in a highly-congested area of an urban driving. The inherent issue with the implementation of stop/start technology in Southeast Asia, with tropical climate such as Malaysia, is the constant demand for the air-conditioning system. This inevitably reduces the duration of engine switch-off when the vehicle at stop and consequently nullifying the benefit of the stop/start system. On the other hand, cylinder deactivation technology improves the fuel consumption at certain conditions during low to medium vehicle speeds, when the engine is at part load operation only. This study evaluates the fuel economy benefit between the stop/start and cylinder deactivation technologies for the actual Kuala Lumpur urban driving conditions in Malaysia.

The accurate confirmation of fuel economy benefits arising from the use of a gasoline additive package is a difficult exercise. In order to fully understand, and accurately quantify, the interaction between the treated fuel and the engine it is necessary to carry out a fleet test which allows the benefit to be measured precisely yet under realistic conditions. A series of road tests, based on a ‘paired fleet’ design, has been carried out over the last two decades. Careful analysis of the results of these tests has led to the design of a new fleet testing protocol based around ‘quads’ rather than pairs of vehicles. This new test protocol also incorporates advances in vehicle selection and preparation procedures and has resulted in a test that is both more robust and flexible, and that achieves even better resolution than before.

Due to the recent drive to reduce CO₂ emissions, the turbocharged direct injection spark ignition (turbo DISI) gasoline engine has become increasingly popular. In addition, future turbo DISI engines could incorporate a form of charge dilution (e.g., lean operation or external EGR) to further increase fuel efficiency. Thus, the conditions experienced by the fuel before and during combustion are and will continue to be different from those experienced in naturally aspirated SI engines. This work investigates the effects of fuel properties on a modern and prototype turbo DISI engine, with particular focus on the octane appetite: How relevant are RON and MON in predicting a fuel's anti-knock performance in these modern/future engines? It is found that fuels with high RON and low MON values perform the best, suggesting the current MON requirements in fuel specifications could actually be detrimental.

Turbocharged diesel engines are widely used in off-road applications including construction and mining machinery, electric power generation systems, locomotives, marine, petroleum, industrial and agricultural equipment. Such applications contribute significantly to both local air pollution and CO₂ emissions and are subject to increasingly stringent legislation. To improve fuel economy while meeting emissions limits, manufacturers are exploring engine downsizing by increasing engine boost levels. This allows an increase in IMEP without significantly increasing mechanical losses, which results in a higher overall efficiency. However, this can lead to poorer transient engine response primarily due to turbo-lag, which is a major penalty for engines subjected to fast varying loads. To recover transient response, the turbocharger can be electrically assisted by means of a high speed motor/generator.

The demonstration benefit from fuel-borne fuel-economy additives to a precision of 1%, or better, traditionally requires very careful experimental design and considerable resource intensity. In practice, the process usually requires the use of well-defined drive cycles (e.g. emission certification cycles HFET, NEDC) in conjunction with environmentally-controlled chassis dynamometer facilities. Against this background, a method has been developed to achieve high-precision fuel economy comparison of gasoline fuels with reduced resource intensity and under arbitrary real-world driving conditions. The method relies upon the inference of instantaneous fuel consumption via the collection of OBD data and the simultaneous estimation of instantaneous engine output from vehicle dynamical behaviour.

The influence of gasoline quality on exhaust emissions has been evaluated using four modern European gasoline cars with advanced features designed to improve fuel economy and CO2 emissions, including stoichiometric direct injection, lean direct injection and MPI with variable valve actuation. Fuel effects studied included sulphur content, evaluated over a range from 4 to 148 mg/kg, and other gasoline properties, including aromatics content, olefins content, volatility and final boiling point (FBP). All four cars achieved very low emissions levels, with some clear differences between the vehicle technologies. Even at these low emissions levels, all four cars showed very little short-term sensitivity to gasoline sulphur content. The measured effects of the other gasoline properties were small and often conflicting, with differing directional responses for different vehicles and emissions.