Oil baffle or "windage screen" functionality

[stevef]

I just found Rob's thread on the "windage screen" inside the 2.2, I'm doing the same thing and are proposing the omit this screen on assembly. Just wanted to get wider opinion on this. Wayne does mention it in his book on earlier engines but I can't find any commentary on the usefulness of the screen


http://forums.pelicanparts.com/showthread.php?s=&threadid=117227&highlight=Baffle

[Tim Walsh]

I don't know how useful it is but I sure know it's a royal PITA. My screen disintergrated for some odd reason (couldn't figure out how) and since I had ferous metal running through my engine I had to tear it down. I don't plan on using even a good screen in my engine anymore.

Basicly, I had to tear down my engine for the porsche equivalent to an appendix

[dtw]

After seeing the carnage inside Tim's engine first-hand, and noting that Porsche elected to delete this component in later years, I decided NOT to install the windage screens in my current rebuild.

[stevef]

Thanks guys, One less thing to clean...and clean....and clean!

[Tim Walsh]

aww come on the carnage wasn't that bad.. I just had ferous metal everywhere and a pound of carbon and rust.........on one piston

[jluetjen]

Just to play devil's advocate, I wonder if Porsche deleted the screen on later models just because they weren't rev'ing much past 6500 RPM any more. At lower rev's windage is not as big of an issue. In an S or a race motor I could imagine that there is a couple of HP generated by the screen capturing oil droplets and pulling them out of the air inside the crankcase.

Much as it is harder to pedal a bike when there is water splashing around in the spoke area, it's also harder to spin the motor with a lot of oil suspended in the path of the crankshaft. Windage screens are a fairly standard item to add when building a race engine which is torn down every couple of years. For a low rev'ing street engine it may not be such a big deal. For comparison the screen that I pulled from the 2.4TK that I'm rebuilding was in fine shape.

Did you ever wonder why it rusted out though? You would think that being enclosed in a nice oily environment would prevent it from rusting unless there was considerable moisture introduced. I think that the another factor that could have an impact would be some sort of reaction between 2 different metals which I believe could cause corrosion, but then all 911's would have this problem.

I wonder if there is more of a story in the case of your engine.

[Jim Richards]

I thought Tim's motor had standing water in some of the cylinders when he first got the car. Maybe the screen was already rusted out at that time.

[Tim Walsh]

yes my motor had standing water in it for about a year and a half but on the other hand the screen was not rusted. The screen had a nice hole in it and at the edges of the hole weren't rusted either. It looked like something punched through it. But we couldn't find anything amiss that would have been moving quickly enough to break the screen. The hole was underneath the Int. shaft and about the size of a quarter. It's really strange but I dont' trust windage screens anymore.

[ValveFloat]

I opted to not put the screens back in my 2.0. The screen itself was in good shape, but the plastic on the edges was cracked and starting to come off. I figured bits of plastic in my oil would be worse than some air, and I also figured since I did the oil-bypass update and a 3.2 pump there should be less oil in the case.

[Wayne 962]

As far as I know, the 2.0 engines were the only ones with the windage tray (subsequently deleted in the later engines). I recommend simply removing them from the 2.0 engines...

-Wayne

[Jay Auskin]

My 2.4L T motor has one. It was in "perfect" shape when I removed it. I'm considering re-installation...why the recommendation to be removed???

[Tim Walsh]

My 2.4T most definitly had the windage tray (72)

[dtw]

Yeah, chalk up 2 more 2.4 engines with 'em for me...

[Wayne 962]

Hmm, are we all talking about the same thing? The parts diagrams don't show in in the 72/73 cars.

The screens are supposed to reduce the amount of oil that is sloshing around in the case, creaing a oil-air environment that is higher friction when engine components pass through it. Typically, dry-sump engines don't have a lot of oil at the bottom of the engine when they are running (the whole point of the dry sump). I know that these screens were removed on the later cars, but that might have been for a number of reasons (larger oil pump, oil pump-bypass, case strengthing ribs changed the geometry inside?).

I'm sorry, I don't have a good answer on this one - perhaps JW or Steve Weiner can weigh in with their opinion?

-Wayne