Date: Sat, 23 Aug 2003 14:35:50 GMT
From: hohnopsamlid.invalid (Goran Larsson)
Subject: Re: does modyfing the crankcase ventilation system do any harm?

In article <>, Simon Putz <> wrote: > are you absolutely sure of that? on my car a there is this small hose > that goes to the intake manifold, and a bigger one that goes down the > right side of the engine and it splits up and one hose from there goes > to the throttle body and another one goes to the intake tube, just after > the air mass meter, next to where this recirculation hose from the > APC-solenoid goes. The crankcase ventilation system on the 9000 basically has two circuits, one used during idle and one used when driving. The thin hose that connects the valve cover to the intake manifold (with a one-way valve midway) draws crankcase gasses when the intake manifold has low pressure in it, e.g. during idle. The bigger hose that connects the valve cover to the inlet of the turbo draws crankcase gasses when the engine is delivering power and the inlet side of the turbo has low pressure. This hose can be blocked by ice when the climate is cold and moist, so it is heated by a coolant tube inside it. That is why the hose "splits" and joins the coolant in the throttle body. > > I really can't think of a single thing to be gained from > > modifying it. > > well reducing the oil deposits was just a thought of mine, but it seems > to be better left alone :) There are some advantages in modifying the crankcase ventilation system, but removing it does not bring any advantages, only severe disadvantages. First some information an why the crankcase ventilation system is needed. If the crankcase does not have any ventilation then the pressure in the crankcase will rise due to combustion gasses that escapes past the piston rings. This will cause seal leaks after a while. Venting the crankcase directly to the air, as was done on old engines, is no longer legal due to polution. Ventilation of the crankcase back into the engine, as it is done on the 9000, is the most common solution today. One disadvantage of this solution is that oil mist is sucked out of the crankcase and deposits inside intercooler and the other inlet components. The new low friction engines, e.g. the one in the 9-5, has lower friction piston rings and therefore produces more blowby gasses. This increases the demand on the crankcase ventilation system. One big difference between the 9000 system and the 9-5 system is that the 9-5 has an oil trap. The big hose from the valve cover goes to the oil trap and then another hose goes from the oil trap to the inlet side of the turbo. A small hose returns the trapped oil from the oil trap to the oil pan (below oil level). A common modification popular amongst owners of tuned 9000 cars is to add an oil trap, often an oil trap for a 9-5, to get rid of the oil deposits in the inlet components. -- G–ran Larsson

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