Hi:
Let me try to explain a little better what happens
The DOF doesn't put pressurized oil into the bearing.
The bearing is usually replaced with a new one that has no outer seal but has the inner seal in place. The '97 to '04 models can have the bearing replaced and start of fresh.
The '05 - '08 cars keep the larger bearing but the outer seal is removed. The bearing gets inspected before proceeding with the DOF installation.
When the engine is running, a stream of oil will bathe the bearing. It's not like we connect an oil line to the bearing and pressurize it with oil.
The pressure of this stream varies depending on the engine's speed. The volume of oil is also very small. Just 100 mL/min at 60 psi.
At idle, with the engine up to temperature, the oil pressure is 20 psi or less. Cruising at 70 mph the pressure is about 60 psi.
Remember that the IMS bearing is spinning so any oil hitting it gets shed by centrifugal force. No volume of oil lingers in the bearing. That's why the stream has to be constant.
The back end of the bearing receives oil but not under pressure so no oil should get into the IMS. It is sealed on the back end.
But even if some oil were to make it into the IMS and become rancid with time, as soon as it makes it back to the bearing it will now be washed away by the continuous stream of oil.
The IMS sits just above the oil level in the oil pan. The oil that gets shed off the bearing after bathing the innards just drips down to the oil pan and mixes with the rest of the oil.
BTW, the oil feed point for the DOF has been provided by the factory, so there's no drilling or tapping into the engine whatsoever. There is one port on each one of the heads that the factory provides and are just plugged with a screw-on plug. The oil galley that feeds these ports are exclusive to them and feed nothing else, so no oil is robbed from lifters or any other part that gets lubrication. Also these galleys are fed immediately after the oil filter and oil cooler so the oil that goes to the IMS bearing is filtered and is at least 35 degrees F cooler than the oil in the pan so it does double duty of lubricating the bearing but also as important it cools it off.
The small amount of oil and pressure that the DOF requires for use does not affect the rest of the engine's oil needs since the oil pressure regulator maintains and regulates the oil pressures.
I hope this explains better how the system works.
If you have any further questions feel free to post them or contact me directly if you want to talk.
Happy Porscheing,
Pedro
Pedro Bonilla1998 Boxster 986 - 311,000+ miles:
[www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)
Racecar spelled backwards is Racecar
"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"
"If you wait, all that happens is that you get older"... Mario Andretti
"Being second is to be the first of the ones who lose" ... Ayrton Senna