TECHNICAL LIBRARY Understanding the PCV and AOS Systems · Generally speaking, all

TECHNICAL LIBRARY Understanding the PCV and AOS Systems 7 Generally speaking, all Porsches 1978 and newer are equipped with a Positive Crank- These two steps will reduce the amount of oil getting into the intake tract. Obviously a case Ventilation (PCV) type emissions device, meaning the engine crankcase has a 8 cleaner intake valve will flow better, providing more power and better fuel economy vacuum source supplied to it from the intake manifold. This is to collect and burn the than a dirty valve. These steps also reduce oil consumption, which helps to protect residual combustion by-products known as “blow-by”. “Blow-by” is combustion forced O2 sensors and catalytic converters from damage due to excessive oil consumption. past the pistons and piston rings into the crankcase. Blow-by in the crankcase is then 9 Specialty oils like Driven DT40, DI40, and DT50 feature a high quality base oil, reduce consumed by running it through the engine again, in an effort to lower the overall vehicle oil consumption AND contain more ZDDP for better engine protection. The O2 emissions. sensors and catalytic converters don’t know how much ZDDP is in the motor oil so it stays where it should – in the crankcase lubricating your engine. These oils can On the Mezger based flat 6 air cooled engines built from 1964-1998, these dry sump contain 50% more ZDDP since the volatility is 67% less than standard base oils. The type oiling systems normally do not require an Air Oil Separator (AOS), but all water higher quality base oil delivers better all around protection and performance. cooled naturally aspirated 9X6, 9X7 and 9X1 Sports-Cars equipped with the Even with the right oil, faulty or dirty injectors can contribute to cylinder bore wash- water-cooled M96, M97 and MA101 engines (1997-2017) require this device for AOS down, further reducing ring seal, allowing for increased blowby and contamination of diagnostics (Except for the GT2’s, GT3’s and Turbo models). The AOS directly affects the the engine oil, all which have a negative effect on performance. Regular use of Top engine crankcase atmosphere by applying a very small vacuum to it by the nature of its Tier fuels, such as Shell V-Power, and fuel system cleaners like Lubro-Moly Jectron or job; it should be named a vacuum-oil separator. In most situations when the AOS fails, Driven Injector Defender will protect your port injected engine from intake and intake vacuum in the engine crankcase rises to an unusually high value. More often than combustion chamber deposits. not, this high vacuum ends up drawing engine oil into the intake system causing excessive exhaust tailpipe smoke. This heavily laden oily air mixture can foul spark Direct injected engines, like those found in 2009 and later Boxster, Cayman, and 911 plugs, contaminate oxygen sensors, catalytic convertors and even possibly ruin various models as well as Cayenne models since 2008 and all Panamera models, do not other sensitive engine management components, e.g. the Mass Air Flow sensor (MAF). have the benefit of port injection to keep intake ports and the intake valve clean. As a Even when the PCV system or AOS is functioning correctly, valve guide and piston ring result, the use of a low-volatility oil is even more important. Driven DI40 is a specially wear, as well as cylinder ovality, all contribute to oil consumption caused by excessive formulated oil that is designed to have very low volatility, meaning you end up with blowby. However, even a healthy engine might consume oil. Remember, Porsche states less intake port and valve deposits. Like with most modern Audi, BMW, Mercedes, that one quart in approximately 600 miles is an acceptable level of oil consumption in a and Volkswagen engines with direct injection, expect to have your intake ports and modern engine with low tension rings. There are several contributing factors including valves cleaned using a process done by the dealership and independent technicians, fuel dilution, however with modern oils volatility is the primary contributor to oil consump- whereby walnut shell media is used to blast and vacuum these deposits away. But tion and PCV/AOS failures. again, using the right oil will minimize the buildup and extend the performance of your direct injected engine and continued use of Top Tier fuels and fuel system cleaners Have you ever torn down a motor and seen oil in the intake manifold? How about an will ensure combustion chamber and piston deposits are minimized. intake valve dirtier than an exhaust valve? Ever wondered why that is? The one word answer is “volatility.” This refers to how much vapor a motor oil releases when it gets hot. For modern Porsche engines utilizing an AOS, measuring the crankcase vacuum is Just as how water vapors rise off a pot of water before it begins to boil, the same thing an excellent way to test for overall engine health as well as for the condition of the happens to motor oil inside your engine. As oil splashes onto the pistons and valve AOS. The only way to definitively test the AOS is to measure the engine crankcase springs to keep them cool, the high temperature causes some of the oil to evaporate. vacuum with a slack tube tester or Manometer (an ultrasensitive vacuum gauge). On Modern engines have a positive crankcase ventilation valve that vents these oil vapors the 9X6 and 9X7 Porsches, the engine crankcase vacuum reading is normally in the into the intake manifold. The oil vapors condense in the cool air/fuel mixture, which region of -4.0” to -6.0” H2O (Inches of water). When an oil separator fails, the leaves the oily deposits in the intake manifold and on the intake valve. crankcase vacuum can rise to -10.0” to -15.0” H2O, or even much worse (-40.0” H2O) depending on the extent of AOS failure. So what can you do? Using a lower volatility motor oil is the first line of defense. Fewer oil vapors mean not as many make it into the PCV system in the first place. More oil is then kept in the crankcase where it belongs. Secondly, not overfilling your engine and keeping the oil level closer to the min. fill level will further reduce windage in the crankcase, reducing load on the PCV system. LNEngineering LLC | 125 Gladiolus St | PO Box 401 | Momence IL 60954 Web: http://www.LNengineering.com | Email: support@LNengineering.com | Phone (815) 472-2939 | Fax (413) 280-9041