Aftermarket July/August 2022 Issue

JULY/AUGUST 2022 AFTERMARKET 25 effect on the combustion process, especially from cold. Therefore, fuel delivery quantity and ignition adjustment are paramount to successful drivability. First generation biofuels compose of oil or sugar-based plants into diesel fuel by pressing and esterification. Sugar-based plants are converted into ethanol by a fermentation process. Second generation biofuels are produced from a variety of energy sources including, organic waste, straw, wood, agricultural waste, old timber, low grade forest, including land set aside for future growth, and fast-growing plant material. Low grade forest growth is normally 15-20 years. Renewable carbon source? Here come the politics. Plants convert atmospheric CO2 into biomass, this renewable energy source can then be subtracted from vehicle emissions. It even has a political expression, carbon credits, or carbon offset. It is accepted that bioethanol fuels have less calorific value than petroleum, however the increase in combustion cylinder pressures make up any differences in power output. Effect Autarkic cold starting, or poor start combustion has now been overcome without the need for preheaters, by re- introducing a cold start manifold injector n17, alloy manifolds and retardation of the ignition profile. Additional cylinder bore treatments will help counteract bore wash during adverse low temperature conditions. There is however a much-modified servicing requirement due to oil pollution increase. Oil replacement occurs every 15,000 kilometres or 9,000 mils or 12 months. Ethanol fuel is highly corrosive with respect to copper, aluminium, and rubber, therefor it is not advisable to operate vehicle’s non- bioethanol compliant. Bioethanol fuels have a similar effect on valve seats as unleaded fuels did on their introduction several years ago. Further attention by Audi in addressing the combustion pressure increases focused on the design and strengthening of the con rods, big end bearings with an additional aluminium layer, and piston crown design. The vehicle electronic control system must have a fuel quality sensor g446. This is fitted in the primary fuel supply line. This is necessary for correct adjustment to varying ethanol percentage. Its function is a capacitive change due to the two-bioethanol content. The sensor outputs a frequency between 55hz equalling 0% bio and 150hz equalling 100% bio. Improvement To improve cold start, Audi took full advantage of their multi-injection control system, with one injection event on the intake stroke. This period corrects for the additional cold start fuel requirement, with two injection events occurring on the compression event, with the timing shifted closer to the ignition point. This is augmented by a fuel pressure of 150bar. A conventional gasoline vehicle would have between 65 and 90bar. There has been some speculation over adverse injector performance with bioethanol fuels. We at ADS have experienced what I would describe as an unusually high number of injector-related problems in recent months. With fuel delivery pressures of 350 bar and above, Care should be taken before attributing symptoms and cause. However, I do understand from a great friend and industry expert, that Bosch are experiencing filter baskets dissolving and or restricting fuel flow through the injector resulting in engine failure. Porsche is another manufacturer experiencing premature engine failures, although I have no evidence that there is any connection between these causes. Other more obvious considerations with injectors focus on the obvious fact that the pintles are mounted directly into the combustion area. Therefore they subject to combustion related deposits. Also, pintles may open out, but not in. Do not pre-judge my comments in this topic as negative to recent developments. I have been an automotive engineer for over 50 years. As such, I take a wider, fact- diven view of the rapid changes I have witnessed, including the comments at the beginning of this subject. As a footnote, BMW and KIA have given directives to their dealership network to recommend named-brand gasoline only, without ethanol content. www.aftermarketonline.net We at ADS have experienced what I would describe as an unusually high number of injector- related problems in recent months ”