With the 3.4l flat six N/a. Where does the pressure come from that seals our piston rings, Is it the oil that's spit into the engine from the oas. Is it from a vacuum? How loose are these engines. If you done away with the oas system, routed some type catch can , wouldn't that work better than sending it back threw the engine?

 

Not sure what you mean by pressure. All ICE designs that use pistons and rings seal the same way (a combination of close tolerances and oil to create a seal).

The reason for an engine to try to breathe the crankcase fumes is due to emissions. You don't want dirty, oily, gaseous and poisonous fumes of every car engine going into the atmosphere, so instead, they are sucked back into the engine to be burned and then filtered by the catalytic converters.

Im sure there's a way to change the AOS, but in all reality, even the lowly AOS on these cars still works just fine for most folks.

 

There is the initial ring tension that helps effect a seal with the engine stationary or while being cranked with the starter.

One "experiences" this when assembling an engine, putting the pistons in their respective cylinders and using a ring compressor to, well, compress the rings so they let the piston slide down into the cylinder.

There is the pressure exerted on the rings during the compression stroke or power stroke that forces the ring down against the bottom surface of the piston ring land and from behind out against the cylinder wall.

You do not want to do away with the AOS.

It is there to not only remove the oil vapor from the crankcase fumes but to do other things that are critial for a long and healthy engine service life.

The AOS comes in for a lot of bad press -- I've been pretty vocal about the AOS a number of times myself -- but murphyslaw1978 has it right when he says the AOS on these cars works fine for most folks.

Sure the AOS wears out but after having been through 3 of these it is not the end of the world. About as "bad" as a water pump developing a noise or a leak or a fuel pump quitting.

The AOS helps whenever possible to keep the crankcase under low pressure. This low pressure coupled with the high temperature of the oil helps encourage fuel and water -- present as normal byproducts of combustion -- to boil out of the oil and this helps keep the oil from being thinner due to this contimination. It also helps fight the build up of acidic compounds in the oil.

It is my opinion that the biggest contributor to "wear" in an engine is the effects of acid in the oil and this is one of the reasons why frequent oil changes help prolong the life of the engine.

Without the AOS you'd take the engine's crankcase ventilation system back to the '50's. Back then sludge formation was a huge problem and engine "rebuilds" (top end or the whole enchilada) were often required at around 50K miles.

If the AOS on your engine is bad replace it and expect to get around 75K or 80K miles (or more) out of the replacement.

If it is still good relax. Be sure the oil is the proper type for the engine. Be sure the engine is not overfilled with oil. Do not run the oil level low just be sure when checked on level ground with the oil up to temperature the oil level reading is not above the max line. Do not run the oil too many miles or too long. Change the oil once a year or for most drivers every 5K miles. (I have adhered to a 5K mile oil change schedule for both my Boxster and my 996 Turbo and both engines are just fine. The Boxster has over 310K miles on it while the Turbo just rolled past 155K miles.)

 

Murphy, Mecster nice explanation on everything. Someone had mentioned that I should change aos if Im going to be getting to dropping my engine. Thanks for y'all time, I enjoyed reading this. Thanks

 

The piston rings in the M96 are " low tension ". If you Search that term you'll find lots more. One of the interesting quirks of the M96 is a recommendation from experts to pin the rings in their original position and not change them in most circumstances. Totally counter intuitive. Always wondered if the cylinder bore material was the main reason.Our delicate little rings are also quite fragile.It is easy to break them if you use clunky piston ring expanders.For insertion, I use a "jug" - just like the factory does in the 911 engine assembly line.
http://flatsixes.com/cars/videos/wat...ly-line-video/
The AOS - there are alternatives - an upgrade(Motorsports version) and simplifications - (Stelan and others) . None of the simplifications work perfectly. The problem seems to be that the A/F ratio never settles in the acceptable range.The Motorsports version is so large that it may be difficult to fit.It is also very expensive.
Here is a discussion and good DIY
https://www.renntech.org/forums/topi...nt-aos/?page=2
There is one useful hack for warm climates and one tool to buy
1. Search for the AOS coolant bypass idea. At least it eliminates one aspect of AOS failure !
2. Search for digital manometer and buy one, connect to a spare oil filler cap and test occasionally.At least you may get some warning it is beginning to fail - again !
Note some of the reported failures of new AOS may because the installer failed to remove all the oil dumped in the Intake from the AOS failure.There is more to that AOS job than simple replacement.

 

Thanks for all this information, wow, nice video,