AOS Failure: what breaks first?

[BYprodriver]

Originally Posted by Gilles

BY, how difficult would be to measure distance between the top of the piston and the plug? Could this help to ensure that you don't have a slightly bent rod?

That will be hard to do. 1st I would remove all the spark plugs & just spin the engine over with the starter, should spin fast & easily. Look for any liquids coming out & identify. (oil, coolant,etc.)

[Deserion]

For what it's worth, when the AOS on my mom's '06 987 failed it wouldn't allow a restart, and also had oil in the intake, exhaust, and cylinders. That's been three years ago now, and aside from a thorough cleaning and a new AOS, it's been fine.

[BYprodriver]

Originally Posted by Quadcammer

those cam plugs typically pop out if too much sealant or carelessly applied sealant is used on the cam covers. It clogs either an oil or vacuum passage (can't remember) and those tend to pop out. Not sure if you've had your cam covers off but look into this.

If you've had an AOS failure, your intake is full of oil. I would pull off the throttle body and cross over tube and get as much out as you can with paper towels. Really get into the plenums.

Given the compression ratio of the motor, I think you'd see more like 180 or so, so one cyl at 200 is odd. 150ish for the rest is fine since the reading is dependent on the seal of the gauge to the cylinder, the strength of the battery, etc.

It is a tiny oil passage at the top of the head. When you pull the green plugs you should be able to see the end of a camshaft, they are tubular& sealed with a 1/4" expansion plug. Make sure that plug is intact. If that head oil passage way is blocked the pressure can blowout the cam plug. Edit, just realized Quadcammer already posted half of what I stated.

[maytag]

Originally Posted by BYprodriver

That will be hard to do. 1st I would remove all the spark plugs & just spin the engine over with the starter, should spin fast & easily. Look for any liquids coming out & identify. (oil, coolant,etc.)

You'll note that your comment about spinning the motor with the starter is precisely the first thing I did, weeks ago. ;-) i guess we're thinking alike.

All the liquid I'm seeing come out of the motor is oil. I've seen no indication of coolant in the oil. Peering into the expansion tank, I see no indication of oil in the coolant.

The couple of specs found in the oil filter are probably not horrible, given the nearly 150k miles on the motor. ??

I'm really hopeful I've dodged the big bullet here. But the are enough things concerning me that I'm probably going to take it slow over the winter.

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[maytag]

Originally Posted by BYprodriver

It is a tiny oil passage at the top of the head. When you pull the green plugs you should be able to see the end of a camshaft, they are tubular& sealed with a 1/4" expansion plug. Make sure that plug is intact. If that head oil passage way is blocked the pressure can blowout the cam plug. Edit, just realized Quadcammer already posted half of what I stated.

Hmmmm..... this is good info.
Couple questions:
1. is the green cam plug the same plug used on the OTHER end of the intake cam? The missing plug is the one above the scavenge pump on the left side. I don't see more than one cam plug listed on pelican.

2. Are you suggesting that this is a wet plug? That if it's removed there would be oil leaking? Because there is no sign of oil around the crooked plugs, nor is there any sign of it around the hole that seems to be missing the plug altogether.

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[maytag]

Originally Posted by Gilles

I have an extra (used) AOS in good condition removed from my 987S that you can have it if you want, shipping it should be a few bucks..

That's very generous of you, Gilles! It's known to be good? I mean, not suspect in the slightest? I'd be interested, and appreciative!

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[maytag]

So, help?
What should be plugging this? (This is the front end of the left side intake cam.) And what would cause it to go missing?

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[Gilles]

Originally Posted by maytag

That's very generous of you, Gilles!

It's known to be good? I mean, not suspect in the slightest?

I'd be interested, and appreciative!

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Maytag, I believe that I have two AOS and one of those should be ok, but would like to know how to test them out of the car..

Hopefully someone can share some light on this (JFP perhaps?)

[krombacher]

Originally Posted by maytag

So, help?
What should be plugging this? (This is the front end of the left side intake cam.) And what would cause it to go missing?
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Significant (air) pressure built up in the crankcase somehow, and popped them out. It May have happened when the AOS was temporarily full of oil during your track spin. The AOS is supposed to create a vacuum in the crankcase using the vacuum available from the intake manifold. If for reason it couldn’t do that momentarily, blowby gasses May build up enough to pressurize the crankcase.

Put the cam plugs back in, and if your missing a cam plug, it’s probably at the track somewhere..

Once all of the cam plugs are back in, in theory you shouldn’t have any more big air leaks into the crankcase. Once you put in the new AOS, the car should run better (probably runs rough right now because it’s sucking way more crankcase air than it should due to:

1) the diaphram in the AOS is probably punctured or ripped, which means it won’t be able to regulate the vacuuum it’s supposed to maintain in the crankcase. The diaphram uses differential air pressure (vacuums, in this case), to function, and with a punctured diaphram, the diaphram will leak pressure to the other side.
2) cam plugs not being in - which will leak lots of air into the crankcase, just like opening the oil cap when the car is running, it will make the engine run poorly.. the AOS’s regulator would open up as much as it can to try to achieve a low vacuum level inside the crankcase, but it won’t be able to achieve it - because too much air is leaking into the engine from the hole (cam plug missing or not seated, or if the oil cap is off). With the regulator fully open, a very large amount of air will be flowing from the crankcase, through the AOS, and into the intake manifold. It enters the engine after the mass air flow sensor, so the engine won’t know about how large the vacuum leak is. It would try to adjust using feedback from o2 sensors (but only once they are fully warmed up), otherwise they’ll be ignored when the engine is cold, and the computer will have no idea it’s sucking in way too much air for the amount of fuel it knows it should have to put in.

[thstone]

Originally Posted by maytag

2) ... any PCV system that includes such an easy path for the oil to dump into the intake, such as we have with this AOS system, seems like a design-failure. For decades, we've been dumping PCV into catch-cans which then vent to atmosphere, or to header-pipes, and drain back to the sump.

Why don't we simply do that with these motors? What am I missing?

These days, venting crankcase/oil vapors to the atmosphere is a no-no in terms of system design for emissions compliance. Could you implement a catch-can approach? Yes. But it depends on how you feel about defeating pollution controls and how closely Utah monitors emissions compliance.

Originally Posted by maytag

Is there a better design on the market already?

Yes, Porsche has a motorsports AOS that eliminates most of the design flaws of the Boxster production AOS. The part itself is $750 and you'll need some mods to make it work.

Porsche Motorsports AOS

Originally Posted by maytag

What are y'all racers doing?

Because of the high cost of the motorsports component and the cheap cost of the production unit ($75), most Boxster racers run the production component and simply change whenever needed (many racers do it at the track between sessions if they see a cloud of smoke).

[maytag]

Originally Posted by thstone

These days, venting crankcase/oil vapors to the atmosphere is a no-no in terms of system design for emissions compliance. Could you implement a catch-can approach? Yes. But it depends on how you feel about defeating pollution controls and how closely Utah monitors emissions compliance.




Yes, Porsche has a motorsports AOS that eliminates most of the design flaws of the Boxster production AOS. The part itself is $750 and you'll need some mods to make it work.

Porsche Motorsports AOS




Because of the high cost of the motorsports component and the cheap cost of the production unit ($75), most Boxster racers run the production component and simply change whenever needed (many racers do it at the track between sessions if they see a cloud of smoke).

Yeah..... I guess that all makes sense. Sure seems like there's a void in the aftermarket, if there isn't a better solution yet. Im'a look at adding in a reservoir, in-line, with some sort of overflow that dumps someplace other than INDUCTION.
Sounds nice.... but probably i'll do exactly as the rest of you do.... haha.

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[krombacher]

I wish the carrera’s AOS was as easy to replace as it is for the Boxsters..

In my Canadian province, emission tests consists of just plugging into the OBDII port, and looking at warnings and how many of the sensors are at their ready state. I highly doubt an oil catch can will caught. Besides, it could be designed to be easily removable. I think it’s good “insurance” , to at least reduce the amount of oil ingested and mitigate damage.

There is currently no backup in our AOS system, as it stands now. It would have to be checked regularly though, because if it’s ignored and there’s an issue, it won’t help if it’s basically full of oil already.

If I create a kickstarter campaign, would there be serious interest? I’m a mechanical engineer (for better or worse), and have access to CFD software, if it’s needed. If so, PM me, with your email address, and your car year and model. If I get enough interest I’ll put a kit together.

Alternatively, if you are going to seriously fit one, please say so, actually follow through, and follow up with photos and test results. I don’t want to do it if you are going to do it.
I’m sick of not having a solution for this.

[maytag]

Originally Posted by krombacher

I’m sick of not having a solution for this.

Check this out:
https://www.ecstuning.com/b-turner-motorsport-parts/complete-turner-baffled-oil-catch-can-kit-standard-flow-6oz/022798tms01-09kt/#tabProductDetails
https://www.ecstuning.com/b-turner-motorsport-parts/complete-turner-baffled-oil-catch-can-kit-standard-flow-6oz/022798tms01-09kt/#tabProductDetails

[Racer Boy]

Hmm, that's interesting. I wonder if anyone has tried it on their Boxster yet. For years these kind of catch cans were used in racing cars, but I don't know how they would work with an engine like our flat-6s that have more extreme challenges than most engine configurations in regards to venting the crankcase.

It's cheaper than an AOS. Who is willing to try one first?

[The Radium King]

does the crankcase need to be under vacuum or just vented?

[maytag]

Originally Posted by The Radium King

does the crankcase need to be under vacuum or just vented?

My understanding of this was that it's still under vacuum. That's what I got from the installation instructions.
I think the vacuum is important.

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[Gilles]

Originally Posted by The Radium King

does the crankcase need to be under vacuum or just vented?

I believe the design of the low friction piston rings requires the crankcase vacuum to seal properly.
.

[maytag]

Can anyone tell me what size (diameter) hose connects the Throttle-Body to the AOS?

I'm going to experiment with a small catch-can plumbed-in there, to catch any/all oil that gets past the AOS, give it a place to condense the vapors and then catch & contain what remains. My hope is that I can end the small smoke-bombs that plague me at the track. Despite how common they are on Boxsters, I keep getting black-flagged for them, and I need them to go away.

It seems to me that as long as this added catch-can & associated connections remain air-tight, then the added volume to the system is probably unimportant. (any disagreements?)

Any reasons you can think of that this won't work?

[Gilles]

Originally Posted by maytag

Can anyone tell me what size (diameter) hose connects the Throttle-Body to the AOS?

Maytag, the AOS has two main accordion hoses, one connects to the T tube where the throttle body attaches to, and the other one goes to a breather valve on top of the block behind the driver seat (4-6 bank)

I replaced them once on my 987 and the by the type of the connectors I don't thing that would be very easy to do unless you modify the way the hoses connect with the entire AOS breather system.

Out of curiosity, why don't you just but two new accordion hoses and replace the old ones? You would be back in business in no time (IMHO)..
.

[maytag]

Originally Posted by Gilles

Out of curiosity, why don't you just but two new accordion hoses and replace the old ones? You would be back in business in no time (IMHO)..
.

Thanks Gilles. I don't think this accomplishes anything for me. I have no reason to suspect my "accordion hoses" are bad, in any way.

What I'm trying to do is eliminate the smoke-bombs which plague Boxster owners at the track, by installing a catch-can after the AOS and before the TB. This would (I'm postulating here) catch whatever amount of liquid oil momentarily overwhelms the AOS.