Running without AOS?

[sparker]

Hi guys,

Simple question (hopefully a simple answer!)

Can I run my car with the AOS blocked off? As in, can I just remove the J tube and block the intake and AOS outlet points? Car is running much better without it..

Appreciate your help!

Sam

[blue2000s]

You do want to ventilate the crankcase. Without it, you'll notice a frothy brown substance built up on the dipstick and in the oil filler neck affectionately known as lung mustard. Basically, all the blowby combustion products and vaporized oil mixes the oil into an unattractive froth that isn't doing much in the way of lubrication.

Does it really need to vent into the intake manifold? Not really, but the vaccum helps to minimize aeration and is friendlier to emisions.

[sparker]

Ok thanks. I will decide if I install a new stock AOS, a motorsport one or a vac pump and catch can I have here...

Thanks again,
Sam

[jhandy]

it is my understanding that the GT3 porsche motor sports AOS can be installed with little modification and it is much more reliable and better than stock.

Catch can is cool and all, but as I understand it, offers not real benifit other than it replaces the AOS that might fail over time.

[BYprodriver]

Motorsports AOS is designed for 2003 & newer Boxster as they have a newer version AOS. OK to block off AOS temporarily if it fails (I keep a plug in my console) but it will run rich as this is a large source of unmetered air the DME counts on. Also the vacum in the case helps the piston rings seal.

[The Radium King]

good dialogue, as i've had the same ideas kicking around in my head. i also *think* i understand the function of the aos - to vent any gases from the crankcase back into the intake for emissions purposes and to reduce oil aeration. the aos tries to pull out any oil that might be sloshing around and want to put itself into the intake. some questions, however:

- while the air introduced by the aos is downstream of the dme, the dme would also read the air/fuel mixture at the exhaust and adapt, so i'm uncertain if removing the additional air provided by the aos has any negative effect.
- lindsey racing also notes that the air introduced by the aos is laced with oil vapour which is non-combustible, so is actually a detriment to performance. at a minimum, it is not a participant in the combustion process, and removal would result in a lean condition (until the DME adapts) as additional air that can participate in combustion fills the void.
- i can see how vacuum would reduce aeration of the oil, but am uncertain re sealing of piston rings? would sealing of piston rings not best be achived by equal pressure on both sides?

from the above perspectives, you have to weigh the increases performance of not introducing crankcase vapours into the intake against the decreased cooling of frothy oil caused by lack of vacuum. then factor in the potential catastrophy of aos failure.

some half measures include a catch tank that vents to atmostphere; it reduces pressure in the crankcase but does not create vacuum. it does not have a 'seperator' but catches any splashed oil and has to be emptied occasionally. both canton racing products and lindsey racing sell catch cans.

another option i've seen is a closed catch system. it's a tank between the aos and the intake that catches any oil should the aos fail. i've seen them fabricated from a small tank and some wire mesh that serves to stop the oil while passing the vapour. a form of failsafe is all it really is.