Gasoline Direct Injection: - The Institute of Motor Industry

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Stratified Charge Mode Homogeneous Charge Mode Port Injection The transition period between homogeneous and a stratified charge by the use of a single direct injector is at best a compromise which is difficult and costly to achieve with a standard system. The recent introduction of a Port Injection system by some manufacturers helps to overcome this transition period more effectively by adopting an additional set of conventional injectors within the direct injection system. The port injection system includes injectors that directly inject highly pressurized fuel into the cylinder, as well as conventional injectors that inject fuel into the intake port. When the engine operates under high load, the intake air cooling effect derived from direct injection enhances the charging efficiency of air fuel mixture and reduces knocking. This allows for a higher compression ratio, which leads to enhanced output performance. When the engine operates at low speed and moderate loads, direct injection and port injection are utilized, reducing knock and facilitating the intake air and fuel to mix properly. This results in enhanced fuel economy and stable fuel combustion. The ratio Homogeneous Lean Charge Mode between direct injection and port injection is optimized according to the engine RPM and load. Even when starting the engine cold, direct injection Q: A Nissan Navara has had the gearbox removed and a faulty clutch replaced. During road test it was noticed that the vehicle was jumping out of 5th gear while accelerating and overrun. When reported to the customer, he assured us that this was not happening before the work was carried out. We have checked that the gear linkage is adjusted correctly and also that the 5th gear appears to select and lock into gear correctly, but it still jumps out of gear. A: It’s probable that the gearbox was not aligned properly during the refit. Most likely cause is one of the engine dowels baulking on the side of its gearbox fitting hole. Because of the mis-alignment, the input shaft is not held securely in the pilot bush of the flywheel. When the vehicle is in motion, because the input shaft is not secure, an oscillation is set up between the pilot bush and the input shaft bearing. This oscillation can cause 5th gear to disengage itself under certain conditions. To rectify this situation, the gearbox will need to be loosened, twisted to the correct position and re-tightened. During the retightening, double check that the gearbox is correctly fitted against the engine. Q: A 2002 Ford Mondeo 2.0 TDCI suffers from intermittent poor hot starting. This has now developed into the engine losing power or shutting down completely whilst the car is being driven. The engine generally starts after a few minutes. The last time the engine stopped, the customer reported that although the engine restarted within a few minutes it again stopped after some 11 miles. It was restarted and the customer drove on for about the same distance when it stopped again. When the engine stops running, the glow plug light flashes. We have not found any W W W . M O T O R . O R G . U K S E P T E M B E R 2 0 1 0 M O T O R I N D U S T R Y M A G A Z I N E 4 3 s docta Auto
MIM Tech Talk engine management DTCs in the system. A: Check the camshaft position sensor. In the past it’s been responsible for many intermittent problems, mostly resulting in short term engine running failures. It’s a fair bet that the sensor will also be responsible for poor hot starting. Change the sensor, ensuring that it’s the latest updated part which is grey (as opposed to black) in colour. Q: A 2005 BMW 3 series E90 has a noise coming from underneath the rear of the vehicle. It’s quite a heavy clicking sound and occurs when the drive is taken up. It only occurs once and then not again until the direction of travel is changed. We have checked the suspension mounting points and bushes which are tight and in good condition. A: Noises such as you describe can often be attributed to dry mechanical joints. The problem is often locating where the noise is coming from. If you have correctly located the rear of the vehicle, concentrate your efforts on the rear axle pinion flange. The contact surfaces between the pinion and the flange have in the past been a source of dry contact clonking or clicking. This usually only occurs during a change of drive direction. Remove the flange, grease the splines of the pinion and reassemble with a new pinion oil seal. Material supplied by in association with s Port Injection 4 4 M O T O R I N D U S T R Y M A G A Z I N E S E P T E M B E R 2 0 1 0 and port injection are both used, enabling quick warming for the catalyst, which results in significant purification of exhaust emissions. Highly atomized fuel is sprayed in a wide fan shape from two injector nozzles to mix well with a large volume of air, enabling the creation of homogeneous air fuel mixture. A multi-hole type injector is often adopted for the port injectors, achieving an excellent atomized fuel mist. Transonic Combustion Future Developments Transonic combustion is one of many new technologies being developed to improve the fuel efficiency of internal combustion engines in both fuel consumption and emission levels. The secret to this system is the heating and pressurizing of petrol before injecting it into the combustion chamber, similar to a direct injection diesel system. This puts the petrol into a supercritical state that permits a fast and very clean combustion process without the use of a spark plug to ignite the air/fuel mixture. The supercritical fluid – which can be petrol, diesel, biodiesel, heptanes, ethanol, and vegetable oil – mixes rapidly with the air when it is injected directly into a specially shaped piston crown. The pressure and the heat are high enough to cause the mixture to ignite without the use of a spark, which permits a uniform combustion process throughout the cylinder. The heating and pressurizing of the fuel reduces the wasted energy normally require to heat up the combustion chamber. The system comprises newly designed fuel injectors, next generation electronic control unit and a high efficiency fuel pump. The system can operate over the full range of load and speed requirements, from stoichiometric fuel ratios at full load to very lean 80:1 ratio at cruise and with a 50% reduction in fuel consumption and nitrogen oxides when compared to conventional fuel injected systems. This system has been developed by Transonic Combustion. Inc., based in Camarillo, CA. The company is currently testing the system W W W . M O T O R . O R G . U K
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Gasoline Direct Injection: - The Institute of Motor Industry

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