SpIcEz

You would get the suction from the intake as in Silks setup.

Silks setup is already capping off the connection close to the plenum.

What I'm suggesting does the exact same thing, except it eliminates the AOS.

Unless I missed something? I did read the whole post and mentioned threads.

Any thoughts?

808Bill

Understood, but will you get the same amount or enough vacuum from the airbox? Silk seems very happy with his set up.

SpIcEz

I would assume Id ge the same amount with or without the AOS, if I hook it up to the airbox like Silk.

Ordered a catch can on Amazon. Will start looking at fittings and hose needed soon. My AOS is failing and I need to address this.

Silk

Removing the AOS is silly. With the modification the AOS stays open and functions perfectly fine as a cyclonal separator. It gets heated by the coolant when necessary. No need to take it out. It will not fail. At least not the typical problem with the diaphragm not closing as there is no more excessive vacuum.

Every healthy engine has a certain blow-by creating an overpressure in the crankcase which gets pushed to and ventilated via the AOS. The moving air in the air-box creates a (slight) under-pressure so it helps evacuate the aos and crankcase.

In case the AOS gets blocked for some reason there is the oil cap vent line to get the overpressure out.

Porsche integrated this safety in the newer engines, see the extra line on the oil filler tube in the 997.2.

SpIcEz

Cant do the oil cap vent on the 986. But maybe i can tap i. Somewhere else.

My AOS needs replacing, trying to avoid having to buy a new one AND do this....

Silk

My indy normally installs it without oil cap vent.
if you dont track your car or dont do very aggressive cornering you can easily go without

SpIcEz

I will be tracking the car. But i'll figure something out for that.

The Radium King

dunno the year of your car, but porsche has been regularly updating the oem part. just make sure you get the latest version from an oem manufacturer that hasn't been sitting on a shelf for an eternity drying out and you should be fine. typically in porsche part nomenclature the last two numbers are the 'version' of that part; i think they are on 04 for the aos at this point?

SpIcEz

Its a 2001 3.2.

The Radium King

http://www.autoatlanta.com/porsche-p...section=104-10

Silk

986 is less problematic for overwhelming the cilinder heads on track which can cause overpressure and pushing out oil via the AOS.

808Bill

Is the oil fill tube on the 996 interchangeable with the 997?

RuVaRo

I have a 996 4S tiptronic 2002 with approx 115.000km and had the same issues with a failing AOS.
Have read a lot about it and how this AOS works and my biggest help to find out was 'SILK' who had already done a AOS-bypass.

About 12 months and 10.000km's ago I had a failing AOS, had a new one installed and now again it failed!
I have had it with this system and am happy there is a solution with the bypass because the AOS is simply not a good standard. At least not the standard I would expect from Porsche, not to say about their solution on the 996's...

With this I want to show you how I did it because in my case the set-up is a bit different because i have changed my original airbox to a Fabspeed airintake, (in combination with a 82mm gas throttle body and IPD plenum)
Hope this helps somebody here.

996 4S Tiptronic AOS bypass without original airbox

Steps taken from beginning of the bypass:
-1- Cut off the large AOS inlet to the throttle body
-2- Large diameter tube to oil catch can, (tube leading over the throttle body / I used clear tubes to have possibility to check fluids going through them)
I had to modify the in- and outlet to oil catch can also to a large diameter
-3- Outlet tube oil catch can to oil filler cap, (tube leading under airintake)

With only this set-up the inlet to the throttle body is still open and here the difference to what Silk did starts with my solution because of the Fabspeed Air intake.
Main issue is to have a bit of airflow (vacuum) same as when you have it when you use a 3rd outlet on the oil catchcan leading into the original airbox as how it is done at Silk's.
This is to prevent an overpressure in the crankcase because of 'blow-by'.

-4- On the oil catch can I used 1 of the 2 unused original in-outlets on top of the oil catchcan, (in photo to the right of the vacuummeter) which has a small diameter, (approx 4 mm) and used with this an airtube, (with a flexibe small diameter tube to connect) and lead this blue tube to the cut inlet to the throttle body. Also this last connection is done with a piece of the larger flexibele tube so it fits better onto the harder original black tube.
This blue tube (return) is long and in the photo it lays below the air filters. I made it extra long to have the air in it cool down as much as possible to have a cooler air-intake.
In the photo you can find in the middle -under the T-bone of the airintake- this bue tube has a connection piece. Easy 'click-on' system when you want to remove... same at the intake to the throttle body.
The other original in-outlet on the oil catch can I blocked off with a fitting bolt.

So this works fine (for me and -more important- for the engine)
I was lucky the small original diameter was just prooving it brings in that bit of vaccum needed

But.... you see more on the photo
This is about this next piece


Connection on 'connection piece' Vent line

This part has been changed to new by me when I did the new AOS last year. It is originally going to the AOS and answers some of the questions I read in this thread.
This is venting the crankcase when something goes wrong with the AOS and/or when there is too much (over)pressure in the crankcase.
I tested this. For example when -in my bypass- I did not use the vacuum from the throttle body, (so, creating a closed system) it created an overpressure and this vent blew oil out.
So, I decided to secure the also with a 2nd oil catch can!
This is the plastic can I made doing some 'McGiver-work'... and will be re-done in near future with a new small oil cath can.

Steps taken:
-1- connected a flexibele tube to the vent (see 2nd photo and when you check it out thoroughy you can see it still has some oil in it from the testing... no harm there because this vent is only for 'going out')
I check this spot after every drive to see if the level has gone up
-2- Connected the flexibele tube to the plastic oil catch can (on top)
-3- outlet on plastic oil catch can leads to a larger 'catch can' just in case, because 'when it goes'... it goes with a lot of oil!)

So, in future it will be a bit more 'tidy' ;-)
Now also looking for the blue tubes in a larger diameter which will be connected using a small piece of the clear larger tubes. With this small piece of clear tube you will be able to check if some oil-flow is happening before it will be visible in the oil catch can
Below an example of a connection like this

This was during testing: AOS going to oil catch can with small diameter. Did not work. In the back you can see the blocked off inlet to the throttle body: did not work. So just to show how it looks like to have possibility to check flow and the connection is much better because the xlex tube fits better to the hrader original tube...

Hope what I showed you here helped you in any way!

soren.911

As I see it you are using the original intake vacuum behind the throttle body and “just” fitted a cath can in between? Then you still have “high” vacuum at idle.
the idea with the “Silk” modification is it eliminate this by moving the line from the AOS to the other side of the throttle body.

RuVaRo

Hi 'Soren.991',
My vacuum is low, lower then before...
'Silk's modification' to the other side off the throttle body? At Silk's it is going to the air intake box...