996 Carrera catch can + AOS

[Mike737]

Has anyone installed a catch can on their m96 engine?

I'm thinking about dropping one in since I've had a bad run with AOS's. First AOS failed a week after I got the car, replaced it and the second one has never worked 100% and is slowly getting worse, got told I couldn't warranty it as it still "works". I'm reluctant to replace the AOS as it's still relatively new and can't be guaranteed that I won't be in the same boat with the new one. I've thought about the motorsport AOS, but been told I'll need to mod to make it fit and the extra costs makes me just want to go catch can.

Tempted to either run it inline with the AOS (ie. AOS -> catch can) or being able to swap between the two when I know there is a potential for AOS to be in the smokey zone.

Anyone had any experience with this kinda of setup?

[Macca]

Have wondered this also - during track day had a puff or too. The upgraded AOS is expensive. 

[Fraz]

 

Cant comment for use on a 911 but I have been using catch cans on my work utes for years. The new VF LS3 V8 is a filthy oily thing. I collect at least 100ml a week.

Check these out mate, great quality and easy to fit.

http://www.eliteengineeringusa.com/

This is probably the one to use.

http://www.eliteengineeringusa.com/best-elite-e2-catch-can-2014-corvette-stingray-w-clean-side-separator-and-check-valves/

 

 

[Pauly]

The 944 turbo guys swear by these

http://www.saikoumichi.com/internal_baffle_design.html

[Mike737]

Bugger was hoping someone in oz had done it. Supposedly just running a can will not provide enough vacuum for the engine to crank, so running without an AOS is a no go unless you can find a can to deliver the right pressure. A few guys in the US are running catch cans inline, but their engines are now VF's like you mentioned @Fraz.

Spent a bit more time researching tonight and came up with the following interesting items.

• The motorsport AOS was actually made for the 996 Koni Grand Am series. 04-05 engines are the easiest to fit, but all engines require modifications and 3.4's are a no go. Jumper5836 reported on rennlist that his oil consumption went up to a litre per 350k with track driving after fitting the motorsport variant! 
• Stelan off the 986 forums made an aftermarket AOS mod for the 986 2.8 engines - http://986forum.com/forums/boxster-general-discussions/64368-stelan-aftermarket-aos.html

Thought about rigging up an AOS relocation kit so it's easier to access the AOS without having to drop the engine every time the dam thing goes wrong. Although I think part of the AOS plugs directly into the block for oil return (right behind the red arrow in this photo http://cdn4.pelicanparts.com/techarticles/Porsche-996-997-Carrera/09-ENGINE-Air_Oil_Separator/images_small/pic17.jpg) so I'm not sure how I could work that. 

[Fraz]

This set up is exactly how the catch can system works on my work cars, except yours on this link http://986forum.com/forums/boxster-general-discussions/64368-stelan-aftermarket-aos.html the hose appears to be a lot bigger diameter from the engine to the throttle body and the oil goes back to the sump. 

The oil is not returned back to the engine on my catch cans. Returning oil to the sump I don't understand, that oil coming out of the engine is filthy oil vapour full of gunk from the combustion process. It smells like burnt oil and fuel with visible contaminates. I can see why Porsche put it back in the engine, what owner apart from someone like ourselves would even think of it, let alone be bothered. I suspect the Porsche AOS is also an oil filter, gets blocked with these contaminates then fails or fills up with oil.

@Mike737 I can't see why the engine would not crank/start due to fitting a catch can as the system is sealed and would not create a vacuum leak. Oil consumption rise is normal using a catch can vs the factory AOS as the oil is not returned to the sump. Obviously you will have to block the oil return line back to the sump of you fit a catch can vs AOS.

What does Mr Nick Cas have to say, surly he has done something like this on race cars.

 

 

 

[Fraz]

@Mike737 how did you go with this ?

[Russ]

have you looked at a Mann ProVent 200? it has a replaceable filter element and is suitable for vehicles up to 250kw

and I'd imagine Porsche sent the oil back to the sump because of emission requirements - they can't really do anything else with it

[Fraz]

have you looked at a Mann ProVent 200? it has a replaceable filter element and is suitable for vehicles up to 250kw

and I'd imagine Porsche sent the oil back to the sump because of emission requirements - they can't really do anything else with it

They could burn it like my ute, oil is sucked in behind the throttle body into the intake manifold. As a result the oil sits in the intake, clogs up the inlet side of the valves and reduces the octane of the fuel.

How they are allowed to do this is beyond me considering the amount of oil I collect each week.

[Russ]

old 911's have the same system - where oil is vented into the air filter housing

not allowed anymore though

[Mike737]

Sorry guys for the lack of response but I've been pretty busy of late.

@Russ is correct in that the oil is sent back due to emission requirements (along with the whole water cooled thing). The ProVent seems great, but there's no way we can plumb anything else in other than the oem AOS due to how it fits into the block.

@Fraz the job of the AOS is exactly what it says, a PCV designed to separate oil from air. They are designed to cool the blow-by gas leaving the engine so that the oil will condense back to a liquid state. Condensed oil is returned to the crankcase and then only the combustion gases are blown out the exhaust.

Nick came up with this gem tonight...

Engine Oil Dip Stick - Dip Stick Tube: All Technical Service Bulletins
Engine - Blue Smoke During High Speed Turns

The culprit is most likely the oil level!!!!! Turns out the dipstick and electronic oil level sensor were adjusted from Jan 2002 to read 1/2 a litre less. My car being an August 2001 build has the 3.4 litre version dipstick and the electronics have been calibrated to that. It seems to fit as every time the oil level dropped to the low point on the electronic gauge the car stopped blowing any smoke during hard driving. We will be fixing this up next service and hopefully the problems should finally be gone!

[firstone]

This is what I found on my 2001 986s as well but I was reluctant to put it forward as a remedy for others not knowing this technical reason. 

Thanks Mike.

[Russ]

can you get an adapter machined for the block and run something external? 

maybe time for the bigger sump mod - http://www.pelicanparts.com/techarticles/Porsche-996-997-Carrera/12-ENGINE-Installing_a_Deep_Sump_Kit/12-ENGINE-Installing_a_Deep_Sump_Kit.htm

 

[Mike737]

This is what I found on my 2001 986s as well but I was reluctant to put it forward as a remedy for others not knowing this technical reason. 

Thanks Mike.

Didn't realise it effected 986's as well. Was it just the 2.7?

can you get an adapter machined for the block and run something external? 

maybe time for the bigger sump mod - http://www.pelicanparts.com/techarticles/Porsche-996-997-Carrera/12-ENGINE-Installing_a_Deep_Sump_Kit/12-ENGINE-Installing_a_Deep_Sump_Kit.htm

 

Have had the deep sump for 2 years now. Gives a nice extra 2 litres of oil which you notice in the wallet when servicing. It's been great when the oil levels say they're low, but I know it's still got 8.75 litres in it. Definitely nice insurance when you're doing hard cornering and braking.

Maybe could make an adaptor for the block but definitely not a home job and probably would need a spare AOS for casting. That's way out of my skill level.

[firstone]

I don't know about the dipstick and recalibration. Only that if my oil is low by 1/2 Lt it blows no smoke on start up or hard cornering.

[Mike737]

The only way previously was to have low oil indicated on the electronic measure which meant I was a whole litre down which is really abnormal. At least now it will only be a 1/2 litre from full.