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Old 06-02-2016, 04:56 PM   #1
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More stupid AOS talk...

So this week I changed out my AOS (again) because last week I had a smoke bomb/flashing CEL at the track. The motor-sport AOS is on my wish list and probably, if I could make the proper decisions, I could have spent less and solved my problem.
So, I cut open the old AOS which had been pumping oil through my intake and causing mayhem, only to find that the diaphragm was like new, no other obvious physical problems whatsoever.
Okay, on the track I'm fairly new (2nd season), I'm running street tires (Mich sport PS2s), I'm not pulling big lateral G's on the corners as if I were on sticky R comps. Is the stock AOS really that bad???
Question: How many of you share this experience, pulling off the hose between the AOS and the intake plenum, to find it bathed in oil?
I've got a sport oil sump baffle coming in from Pelican next week with some other necessities and am hoping it will help! I've heard talk about a catch can, but the jury seems to be still out.
Talk to me.
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Old 06-02-2016, 05:20 PM   #2
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Assuming that your AOS is working (max of 5 inches or water steady vacuum at the oil filler cap), you are always going to find the hose from the AOS to the intake coated in oil, that is simply a fact of life. Adding a catch can will only coat that as well.

The AOS is designed to reduce the amount of liquid oil pulled into the intake system, but not to eliminate it completely. The problem is that oil is being transferred as vapor when the engine is running hot, and that vapor accumulates on everything it touches. That also happens with the motor sport version as well.

If you are smoking badly at the track, and the AOS is working properly, the problem lies elsewhere, as in the AOS system pulling liquid oil out of the cam covers.
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Old 06-02-2016, 06:17 PM   #3
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Quote:
Originally Posted by JFP in PA View Post
If you are smoking badly at the track, and the AOS is working properly, the problem lies elsewhere, as in the AOS system pulling liquid oil out of the cam covers.
How does this happen?
p.s. It's not smoking badly. This is only the second time that it has happened.
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Old 06-02-2016, 08:19 PM   #4
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I've had the extreme smoke bomb action on my '02 at the track recently as well. I've ordered a new AOS, special oil pan baffles, and "deep sump" kit to lower the oil pan 1/4". Based on what I've read, that commonly solves the problem.

I'm really hoping it does!
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Old 06-03-2016, 05:12 AM   #5
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Quote:
Originally Posted by NewArt View Post
How does this happen?
p.s. It's not smoking badly. This is only the second time that it has happened.
At speed, your cam covers have a lot of oil in them; add G=loads in corners and some of that liquid oil can get sucked into the AOS system (which has a vacuum line running to each cam cover). While the AOS can handle some level of liquid oil, it cannot deal with a flood, and more than normal vapor gets sucked into the intake.

Porsche had been aware of this for a long time, and actually produced an exotic and hyper expensive kit (read $10K+) for the heavily tracked 996's to help limit it. Amongst other things, the kit contains a "north west passage" oil recovery system which consists of additional oil scavenging pumps in the cylinder heads with lines to run the oil back to the sump. Unfortunately, this kit was never made available to fit in a Boxster.
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Old 06-03-2016, 05:21 AM   #6
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And, unfortunately, I don't have a spare $10K+ even if it were available!
Oh, and thanks for that explanation!
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Old 06-03-2016, 01:18 PM   #7
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Suggest you read up threads about installing the deep sump and baffles. If you put the horizontal plate-baffle in the wrong place, if the 'windows' jam open ,if the pick-up tubes aren't the right ones - it will be sub-optimal.
It seems the cheaper sump spacer+baffle kits work but only with intelligent fitting & fiddling . The deep sump kits (Mantis/Brey Krause?) seem to work better out-of-the-box.
Need to check your vac system too. An inexpensive paint-can smoker works well.
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Old 06-03-2016, 01:32 PM   #8
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Quote:
Originally Posted by JFP in PA View Post
At speed, your cam covers have a lot of oil in them; add G=loads in corners and some of that liquid oil can get sucked into the AOS system (which has a vacuum line running to each cam cover). While the AOS can handle some level of liquid oil, it cannot deal with a flood, and more than normal vapor gets sucked into the intake.

Porsche had been aware of this for a long time, and actually produced an exotic and hyper expensive kit (read $10K+) for the heavily tracked 996's to help limit it. Amongst other things, the kit contains a "north west passage" oil recovery system which consists of additional oil scavenging pumps in the cylinder heads with lines to run the oil back to the sump. Unfortunately, this kit was never made available to fit in a Boxster.
" Adding a catch can will only coat that as well."
I had hoped that someone(Stelan?) would publish a diy catch can solution by placing a Catch Can ahead of the AOS to divert liquid oil direct to the sump. From what JFP and Porsche R&D have discovered it seems unlikely that a cheap,simple catch can would be effective?
see post #8 in this link to a previous discussion:
http://986forum.com/forums/general-discussions/60203-new-aos-failing.html
So time to investigate other contributory factors like lack of anti-foam additives in the engine oil?
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Old 06-03-2016, 01:50 PM   #9
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Problem is that the AOS system draws vacuum on both cam covers and thereby the sump. Even at only 5 inches of water, hot oil is going to give off some level of oil vapor, as well as other vapors (we will get back to that in a moment). To limit the vapor transmission to the intake hose (read vacuum source), the catch can device needs to be cooled to condense this vapor back to a liquid. This presents a couple of issues: Where to put the two devices (one of each bank, otherwise you would need one larger unit), how to cool them and keep them cool in proximity to a hot engine, and how to get the condensed vapor separated (some of it is oil, some is water, some is fuel) so that only the oil portion is returned to the sump. You would also need to figure out how to dispose of the non oil components from the cans as well because you do not want them returning to the oil system. (currently, they are sucked as vapor into the intake and burned).

Add in conditions where there is an overly large amount of liquid oil being thrown about the inside of the cam covers (high RPM and g loads in the corners at the track), and now you have some liquid oil entering the catch can system as well. This also has to be handled at the separation stage.

None of this is insurmountable, but it would take some very intricate engineering (read expensive) to make it all work.
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Old 06-05-2016, 08:57 AM   #10
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AOS units simply are not lasting these days. The latest run from Mann has proven to have issues, as I have experienced them several times in the last couple of months.

We've been testing a product for a while thats almost far enough along to pitch to distributors. If they accept it, the AOS problems will be over.
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Old 06-05-2016, 09:15 AM   #11
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Quote:
Originally Posted by Jake Raby View Post
We've been testing a product for a while thats almost far enough along to pitch to distributors. If they accept it, the AOS problems will be over.
Hello Jake,
Sounds very interesting, are you talking about a new AOS design, or new internals for the existing AOS..?
Regards,
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Old 06-05-2016, 11:11 AM   #12
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Good luck with the new product Jake !
I am surprised a diy system using a small,brushless 12v vac pump + adjustable pcv+catch can +check valve has not been tried.
That would allow an AOS delete.
Some hot rod/race guys do this.
http://www.hobbyexpress.com/power_25_bl_outrunner_motor_1250kv_1036351_prd1.ht m
http://grannys.tripod.com/evac.html
http://mewagner.com/

Last edited by Gelbster; 06-07-2016 at 07:41 PM.
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Old 06-07-2016, 07:39 PM   #13
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Quote:
Originally Posted by Gelbster View Post
" Adding a catch can will only coat that as well."
I had hoped that someone(Stelan?) would publish a diy catch can solution by placing a Catch Can ahead of the AOS to divert liquid oil direct to the sump. From what JFP and Porsche R&D have discovered it seems unlikely that a cheap,simple catch can would be effective?
see post #8 in this link to a previous discussion:
http://986forum.com/forums/general-discussions/60203-new-aos-failing.html
So time to investigate other contributory factors like lack of anti-foam additives in the engine oil?
I will try to get the time to write a good diy on my custom AOS
I have been all over the place due to work but will try to find the time
Steve
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Old 06-07-2016, 07:51 PM   #14
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Steve,
You also squandered time restyling the Boxster into something far better looking and more functional that Dr. O did ! So you are forgiven for neglecting te AOS hack write-up :-).
As you can see there is great interest in your system !
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Old 06-08-2016, 05:34 AM   #15
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Also looking forward to Stelans DIY. Would a sketch be worth a thousand words?

Your verbal description sounded pretty good.

I understand you are short on time so to help I have sketched what we think you built from the description and you can correct and fill in any missing details.

Could you folks submit corrections, clarifications and Pics and I will improve this 1st draft drawing.
Particularly pics/drawings of what the lines connect to and material sources.



Quote:
Stelans DIY AOS Build:
I purchased a 1 quart stainless steel (aluminum will work too) cylindrical container with a screw on cap, the cap is the size of the entire opening, I welded 3 bungs at the bottom, at the same level, meaning at the bottom, two were 1" and one was 1/4 npt
Then I took a long 1" rubber hose and ran it from one bung of the container to the vent fitting on the drivers side of the engine and clamped, I also capped the check valve opening on this fitting.
Then a very short section of the hose from the second bung from the container and installed right over the original AOS location tube coming straight up from the block (where the accordion rubber boot connected originally).

Then a small 1/4" hose to a piece of tubing that I machined a couple of slots and installed orings and inserted into the small block opening where the small fitting used to be.

placed a stainless steel mesh on the inside bottom of the container, then filled with washed and rinsed stainless steel wool, (use the heavy duty one not the fine one that may break and get pieces of ss into the block) I tested the one I use by pulling and compressing and basically distressing it and it did not flake or break).
then another stainless steel mesh disk on top of the ss wool.
Then I drilled the cap and installed a grommet to accept a standard vw PCV valve (which is exactly a diaphragm like the one we are replacing) one from a vr6 I believe is the one I purchased for about 16 or 20 bucks but you can use from a volvo or a vw1.8t. and connected another section of 1" rubber hose from the pcv valve to the throttle body to replace the j-tube and clamps

After 3k mile trip the inside of the intake, throttle body, etc are dry as dry can be.

This are the benefits I see.

- Next time the diaphragm fails it will cost me a few bucks and it takes 2 minutes to change.
- the thousands of swirls that the steel wool provides to condensate and separate the oil from the vapor are way more efficient than a single empty swirl cavity in the OEM AOS

-I can open the can anytime to see what's going on inside every oil change, last time I checked after that long trip only the bottom part of the ss wool was a little oily.

-I actually got rid of the remote oil fill in the trunk and long dipstick at the same time as they were bad as well, I installed a freeze plug on the top and now I fill my oil thru this new AOS can. and I fabricated a new short dipstick that is marked every quart exactly. I got rid of many potential vacuum and oil leaks all at the same time.
(one disavantage of this is that I have to open the engine cover if I want to chek my oil level but the good thing is that my dash gauge is calibrated accurately)

- My new redneck AOS actually pulls vapor thru all 3 openings in the engine and it drains oil thru ALL 3 of them too so the container will never fill up. (versus the OEM AOS with it's small drain).

- By replacing all plastic tubes with rubber hoses the crack-prone and vacuum leaks are virtually eliminated (and by instaling clamps and not o-ring clips as OEM too)

-The main function of the diaphragm (glorified PCV) is to let vapor go from the inside of the engine block back into the intake where it will be burned. but has to do this at a certain pace and under certain conditions:

1 - when idle (high intake vacuum) the diaphragm closes so the engine does not sees this a vacuum leak. (that's why many bad AOS's give you a CEL and rough idle.)

2- under load (medium intake vacuum) open and closing to let most of the vapors go thru and burn.

3 - Cruising (no intake vacuum) completely open so all fumes get burned.

Another way of doing this is to take the hose from the top of the container (without pcv valve) and instead of running to the throttle body, run it to your air filter box, then you are completely bypassing the problem and you will never need a new diaphragm anymore (you will need to plug shut the throttle body opening)

Regardless you need tu pull fumes from the engine block to keep your oil healty and to avoid pressure build up tha causes oil leaks at the IMS, MBS, spark plug tubes, etc.

So that's it
Steve
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Old 06-08-2016, 06:17 AM   #16
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Quote:
Originally Posted by Jake Raby View Post
AOS units simply are not lasting these days. The latest run from Mann has proven to have issues, as I have experienced them several times in the last couple of months.

We've been testing a product for a while thats almost far enough along to pitch to distributors. If they accept it, the AOS problems will be over.
Please let it be yes, if you want an additional tester I volunteer
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Old 06-08-2016, 08:05 AM   #17
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AOS hack/upgrade Stelan's mod

Great dwg !
Suggest the vac port is moved to the top of the 'catch can' + a dip tube inside.This may avoid sucking condensed oil/fuel vapors into the inlet?
That is the conventional catch can arrangement.
Mounting the new can as high as possible may also help drainage and avoid it getting swamped with liquid oil?
IMHO this drawing is worth using as the basis for a new AOS-mod thread.
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Old 06-08-2016, 11:14 AM   #18
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Quote:
Originally Posted by Gelbster View Post
Great dwg !
Suggest the vac port is moved to the top of the 'catch can' + a dip tube inside.This may avoid sucking condensed oil/fuel vapors into the inlet?
That is the conventional catch can arrangement.
Mounting the new can as high as possible may also help drainage and avoid it getting swamped with liquid oil?
IMHO this drawing is worth using as the basis for a new AOS-mod thread.
So the Middle port on the bottom should move to the top and have a "Dip Tube"?

Like this?
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Old 06-08-2016, 02:35 PM   #19
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Here you go, sorry about the missinformation as the pcv is not from a vr6 but a 1.8turbo vw. vr6 one will work but the 1.8t is a little lower profile and has only two ports
also there are a couple of things I do not remember exactly like the size of the barbed fitting that I use with orings and rtv into the small engine block oil return, perhaps if someone does this we can update some of those details in the drawing, all 3 ports where there are oil vapors need to be at the bottom, so all fumes go thru the ss media and condense oil into liquid to be returned back to the block, on top it should only be the pcv port with clean air/vapors
this drawing also includes a coouple of corrections and changes as the large hose is actually not 1" but a little larger in diameter and as not everybody has access to a lathe turn the small fitting is updated with a double barbed fitting, also this shows the bulkhead bottom fittings with nuts and rubber washers ahas not every one has a tig welder to weld bungs


Last edited by stelan; 06-08-2016 at 03:10 PM.
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Old 06-08-2016, 02:52 PM   #20
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Quote:
Originally Posted by Gelbster View Post
Steve,
You also squandered time restyling the Boxster into something far better looking and more functional that Dr. O did ! So you are forgiven for neglecting te AOS hack write-up :-).
As you can see there is great interest in your system !
thanks, I get very little time of fun due to traveling so much but I will soon retire and have fun full time, lol

Last edited by stelan; 06-08-2016 at 02:55 PM.
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