More stupid AOS talk...

[JFP in PA]

Originally Posted by Smallblock454

Hello,

does anybody know the inner diameter of the vacuum lines needed?

In general these hoses have to be fuel and oil resistant. So i would think more something like fabric reinforced fuel lines. Also had the idea of silicone lines, but silicone seems not to be oil and fuel stable. Also it has to be ethanol stable.

Regards, Markus

Only problem is that the AOS unit uses "click on" hose ends which are vastly more failure prone than the hose itself:

[Nine8Six]

Originally Posted by Smallblock454

Hello,

does anybody know the inner diameter of the vacuum lines needed?

In general these hoses have to be fuel and oil resistant. So i would think more something like fabric reinforced fuel lines. Also had the idea of silicone lines, but silicone seems not to be oil and fuel stable. Also it has to be ethanol stable.

Regards, Markus

Just saw this thread, brilliant idea from Stelan, a new-must for the corner-heavy track I'm assuming.

@Markus - the material you are looking for is called composite for hydrocarbons. "Composite Hose for Hydrocarbon" (Schlauch für Kohlenwasserstoff) for instance should return data from your nearest hardware supplier.

[Smallblock454]

Hello Gelbster, hello JFP in PA,

JFP in PA: thanks for adding the picture. Pictures say more than words.

In general it seems that the AOS component (diaphragm) and the connectors seems to fail. The rest of the system seems to be stable. Rubber hoses will always fail if they transport oil. It's just a matter of time and quality and heat cycles.

First, i'm not a engineer, but maybe some aspects we should consider – also a summary of the aspects you have given to the discussion (hope i didn't miss something).

• The hoses have a defined diameter. That means they have a defined maximum flow capacity.

• If the hoses are too stiff that can lead to problems caused by vibrations. Especially when the AOS / catch can is mounted to the car chassis.

• If the hoses are too elastic they may collapse by underpressure.

• The special connectors can be a problem. I don't know if the connector at the throttle can be replaced – never changed an AOS at the 096 myself.

• The hoses must be oil resistant and to some level they should be fuel and ethanol resistant. i don't think fuel and ethanol will be a main problem, because in general the fuel / ethanol part in motor oil is low. But old oil can contain aggressive substances, even if it is full synthetic.

• We need to define how tong the complete system should work without failing.

I would say if the AOS system works for 15 years without failing it will be OK. What do you think?

Mostly the aspect with Porsche classic parts is that they are expensive because they are Porsche classic parts; not because they are expensive to make.

So i did a research on both hoses and connectors and AOS. There are 2 hoses that lead to the AOS housing and it seems that they both have these special connectors on both ends. Also they differ from model year and in part numbers. So it looks like Porsche has improved the parts and you should always look for the newest version. Also the lines differs from model to model, so there might be problems to offer an one fit all solution.

AOS: 4 different versions:
- 97 A 996 107 023 51
- 98 A 996 107 023 01
- 99 A 996 107 023 04
-> 03 A 996 107 026 01

Part number 4 (hose):
Until 2002 (DE): A 996 107 147 53, A 996 107 147 54, A 996 107 147 55
From 2003 (DE): A 996 107 147 58

Part number 5 (hose):
Until M 65x 01419 (DE) 996 107 145 06 (M96.20)
Since M 65X 01420 (DE) 996 107 145 06 (M96.20)
M96.21/22 / M 96.23/24 996 107 145 06

The hoses themselves are not ultra expensive. At Amazon they are around 40-70 USD. Which is a lot of money, but not ultra overpriced for Porsche parts. And i think you could get them cheaper elsewhere.

So where to go from here? Honestly i don’t know. I don’t know if the parts are really different in detail. If they are, this will be a bigger puzzle than i thought first.

What do you guys think?

Thanks & regards, Markus

[Gelbster]

Big advantage of the Stelan AOS is that many of these issues are eliminated because the stock AOS ,problematic connectors/fittings are eliminated or generic items substituted in brass(not plastic)

[JFP in PA]

Originally Posted by Gelbster

Big advantage of the Stelan AOS is that many of these issues are eliminated because the stock AOS ,problematic connectors/fittings are eliminated or generic items substituted in brass(not plastic)

How does he resolve the click on fitting that is molded into the plastic intake behind the throttle body?

[BYprodriver]

Originally Posted by JFP in PA

How does he resolve the click on fitting that is molded into the plastic intake behind the throttle body?

Maybe increase the hose diameter to go around it & get clamped in place. The connecting tube is 26mm diameter with a 28mm "barb".

Increasing hose diameter may reduce the vacum signal enough to effect ring seal though.

I wonder why the 97 AOS with the horozontaly oriented diaphram was replaced with the vertically oriented diaphram?

[JFP in PA]

Because oil used to sit on the diaphragm, weakening it with time.

[stelan]

yes hose diameter is larger and it clamps over the fitting, the clicker is the part that is removed the part left is great for having a hose and clamp as it has a barbed-shape fitting.

hoses that are design for air/oil will outlast the brittle plastic ones, and yes those click on connectors work great for years then they are very problematic once hard plastic starts to degrade.

[SpIcEz]

stelan, if you are still out there, can you please give us a longterm review of your setup.

1. Has it been holding up?
2. Any thing fail or brake down since?
3. Has it resolved all AOS issues since?
4. Any relevant comments on this?

got an AOS failure and about to start tracking the boxster. Im stuck between starting the endless AOS replacement cycle or buying a motorsports AOS for a brick of gold.

On the other hand, your setup might just resolve all of this.



Thanks,

Chris

[particlewave]

Originally Posted by SpIcEz

stelan, if you are still out there, can you please give us a longterm review of your setup.

1. Has it been holding up?
2. Any thing fail or brake down since?
3. Has it resolved all AOS issues since?
4. Any relevant comments on this?

got an AOS failure and about to start tracking the boxster. Im stuck between starting the endless AOS replacement cycle or buying a motorsports AOS for a brick of gold.

On the other hand, your setup might just resolve all of this.



Thanks,

Chris

From what I understand, the design had a fatal flaw. Stelan seems to have taken $200 deposits from people in Nov. 2016, then just disappeared. It's been 2.5 years since anyone has heard from him.

He was a good guy, so it really makes me wonder what happened...

[Quadcammer]

I believe i found a catch can setup that will work well and it should be less than 100 bucks. It basically sits in line between the aos and the intake.

[maytag]

Originally Posted by Quadcammer

I believe i found a catch can setup that will work well and it should be less than 100 bucks. It basically sits in line between the aos and the intake.

Interested!
Pics?

Sent from my SM-G970U using Tapatalk

[Quadcammer]

https://www.amazon.com/Moroso-85486-Separator-Mustang-4-6L/dp/B006JZ97EU

that is the unit, prices have come up a bit, but with coupon codes at jegs/summit, shouldn't be bad.

The mounting bracket has a single hole. Remove the ground strap nut, slide the bracket on, retighten nut. Its a tight fit to the forward passenger tab for the engine cover but it'll go.

Will take some pics later this weekend, but with the exception of 2 angled reducer fittings from home depot, its basically plug and play.

[The Radium King]

some good recent threads on the rennlist 996 forum on this. basically, if you replace the aos with a catchcan (or an aos with a higher-flow diaphragm) then you introduce too much crankcase vapour during high vacuum idle situations (ie when you come off throttle after wot) and screw up idle fuel trims.

if you put a catch can after the aos then it has to be of sufficient size/volume to make a difference should the aos fail.

one solution that seems to be effective is to vent the aos to the airbox. i have yet to research it to any degree (i am of the 'just use the most recent version of the aos and you will be fine' school) but apparently it doesnt foul the air filter too much, and the airbox is of sufficient volume to hold the oil should the aos puke up. not certain if there is sufficient vacuum at this location to positively vent the crankcase, or if this vacuum is even necessary.

[JFP in PA]

Originally Posted by The Radium King

some good recent threads on the rennlist 996 forum on this. basically, if you replace the aos with a catchcan (or an aos with a higher-flow diaphragm) then you introduce too much crankcase vapour during high vacuum idle situations (ie when you come off throttle after wot) and screw up idle fuel trims.

if you put a catch can after the aos then it has to be of sufficient size/volume to make a difference should the aos fail.

one solution that seems to be effective is to vent the aos to the airbox. i have yet to research it to any degree (i am of the 'just use the most recent version of the aos and you will be fine' school) but apparently it doesnt foul the air filter too much, and the airbox is of sufficient volume to hold the oil should the aos puke up. not certain if there is sufficient vacuum at this location to positively vent the crankcase, or if this vacuum is even necessary.

It DOES matter, without the five inches of crankcase vacuum, the low tension piston rings will not seal properly, leading to loss of power, blow by into the crank case, etc. I can see adding a puke can between the AOS and the intake vacuum port, but not rerouting the vacuum source elsewhere.

[The Radium King]

Originally Posted by JFP in PA

It DOES matter, without the five inches of crankcase vacuum, the low tension piston rings will not seal properly, leading to loss of power, blow by into the crank case, etc. I can see adding a puke can between the AOS and the intake vacuum port, but not rerouting the vacuum source elsewhere.

well, i do understand that porsche uses low tension piston rings, and that they require vacuum to work, but have yet to find a definitive source to confirm the 5" of vacuum value, and also what vacuum is present in the airbox. note that vacuum is present in the intake tract in two ways; at idle with the throttle closed, and as well due to venturi effect as air rushes by. the aos doesnt really want idle vacuum (too high, and vacuum more necessary at higher rpm) however aos returns at that location for emissions reasons.

there is also the more thoughtful perspective: the detrimental effects of blowby vs the detrimental effects (hydrolock) of total aos failure. again noting unless a catchcan can hold a substantial % of the 9 litres of oil in the engine then your 2.5/2.5/2.7/3.2 litre engine is still at risk.

[JFP in PA]

Originally Posted by The Radium King

well, i do understand that porsche uses low tension piston rings, and that they require vacuum to work, but have yet to find a definitive source to confirm the 5" of vacuum value, and also what vacuum is present in the airbox. note that vacuum is present in the intake tract in two ways; at idle with the throttle closed, and as well due to venturi effect as air rushes by. the aos doesnt really want idle vacuum (too high, and vacuum more necessary at higher rpm) however aos returns at that location for emissions reasons.

there is also the more thoughtful perspective: the detrimental effects of blowby vs the detrimental effects (hydrolock) of total aos failure. again noting unless a catchcan can hold a substantial % of the 9 litres of oil in the engine then your 2.5/2.5/2.7/3.2 litre engine is still at risk.

First of all, the air box is open to the atmosphere, there is no vacuum, only flow. Check it some time with a digital manometer, if anything you will find a slight pressure at speed, which is why I laugh at aftermarket cold air systems.

Five inches of water is the nominal value for a new, factory AOS. Higher or lower values lead to problems, so you have to assume 5 inches of water is the system's designed "sweet spot", and which is actually controlled by the AOS itself.

A small catch can is only going to keep small amounts of oil out of the intake system; if AOS failure or track dynamic's lead to it inhaling liquid oil, not much is going to help as the small can will be overwhelmed, while too big a unit is going to result in you grenading the engine when all the oil disappears at speed. Either way, you lose.....

[The Radium King]

Originally Posted by JFP in PA

First of all, the air box is open to the atmosphere, there is no vacuum, only flow. Check it some time with a digital manometer.

Five inches of water is the nominal value for a new, factory AOS. Higher or lower values lead to problems, so you have to assume 5 inches of water is the system's designed "sweet spot", and which is actually controlled by the AOS itself.

flow across the end of a tube can create suction, so if the tube is introduced at an appropriate place in the airbox or elsewhere upstream of the throttle then there is opportunity for vacuum, but no idea if sufficient. note the 997.2 that appears to vent the heads directly to the intake tube while the crankcase goes to the plenum via an aos (if i am reading the parts diagrams properly).

[The Radium King]

vacuum is not really constant anywhere in the system is it (except perhaps at idle)? how does the 997.2 aos operate?

[JFP in PA]

All the AOS operate the same way, they are a throttling device, not unlike the cooling system's thermostat, the take a relatively high vacuum level at the intake (well over 20 inches of mercury) and reduce it to a level (five inches of water) conducive to controlling the low tension rings pressure against the cylinder liners. Regardless of how high or low the intake vacuum level is, the AOS will hold that steady five inches of water in the sump. As a comparison, you cannot even see 5 inches of water on a vacuum gauge calibrated to inches of mercury. One inch of water is only 0.0734824 inches of mercury, so five inches of water is only 0.367 inches of mercury, not enough to even move the needle on a tool calibrated in inches or mercury, hence the need for manometer to read the lower vacuum levels accurately.