csubtil

Hi forum,

Porsche newbie here, so maybe I am asking a stupid question...

AOS venting oily vapors back to the intake and the potential risk of a bad AOS throwing oil into it, doesn't really seem a nice solution...

Isn't possible to keep the AOS but disconnect it from the intake and reroute its venting to the atmosphere? Using a small filter on the tip of the venting pipe to avoid any unfiltered air being sucked.

I know it's not nice to the environment but I am just questioning if it's technically viable or if it will harm the Engine.

Can someone post a pic of where exactly is the AOS connected to the intake?

If what I am suggesting is possible, has anyone in the forum done it?

Is the AOS basically a crank case breather?

I was thinking of something like this

Thanks.
CS

Macster

The AOS is more than a crank case breather. It is as the name implies a air oil separator. It needs air flow to work. The air flow comes from the pressure difference between the crankcase and the intake system.

Additionally during some time the crankcase operates under low pressure. When the oil is hot this helps the unburned fuel and water boil out of the hot oil and this keeps these fluids from reaching the point of compromising the oil.

Part of the reason older engines didn't last long, had horrendous sludge build up and so on was due to the just venting crankcase fumes to atmosphere. Actually even back then there was some attempt at producing low air pressure in the crankcase since the end of the crankcase draft tube was cut at an angle and when the car was moving down the road this created a low pressure at the tube opening which helped pull vapor out of the crankcase.

Only a handful of engines are negatively affected by a failing AOS beyond the inconvenience the failure brings about.

Replacing the AOS with some crankcase breather open to atmosphere would negatively affect all engines, requiring more frequent oil/filter services and even possibly "engine flushes" to remove the sludge build up.

I'm the first to admit the AOS sucks but it sucks less than any other crankcase venting system.

Actually the AOS sucks more which in this case is a good thing. It sucks out the crankcase vapor and removes the oil from this and helps remove unburned fuel and water from the oil.

nick49

Many race motors use a catch can. This is a container with crankcase vent hoses, sometimes trans, diff , battery and radiator overflow hoses running into it to collect condensed fluid vapors. Many will have a filtered vent at a high point and a drain at the bottom. This keeps oily vapors out of the intake and also from spitting on other drivers or the track. I've not researched the 996 motors but I don't know why it wouldn't work. Generally what I have seen, recirculating these vapors is to keep them out of our atmosphere and to help keep our air clean.

perryinva

You could put a catch can on the line between the AOS and the intake. I thought about it, but when I replaced my (still working fine) AOS, the intake valves were so clean, I decided it would be a waste.

TomF

There is a thread about this somewhere on the 996 board. IIRC, it was within the last year.


Cheers,
TomF

utkinpol

i saw such solutions on some cars with FI systems but my mechanic told me that it affects pressure balance and is not good for the motor so it is not getting done, usually. most people install motorsports aos and use it as motor was designed.

jrgordonsenior

The pressure balances also effect foaming in the sump. I wouldn't mess with that....

Byprodriver

The engine needs that vacum source to maintain a vacum in the crankcase in order to help the low tension piston rings seal.

csubtil

Thanks forum for the replies.

CS.

trendy996

If you don't want to use the intake as your pressure source then have an exhaust valve welded into your exhaust to pull pressure. You'll want to weld in after your cats if you are still running them.