Catch Can instead of the AOS...anyone tried it yet?! - 986 Forum - The Community for Porsche Boxster & Cayman Owners

rob76turbo · 08-10-2009, 03:13 PM

Some of my non-Porsche racing buddies use oil catch cans (some use two...one per side). Anyway this has me thinking, has anyone tried to modify the Boxster to use a oil catch can? They can be pretty small, fairly inexpensive...but on our cars the key is where to install it. I am thinking about in the rear trunk area (maybe just besides the area where the oil and coolant tops are located). Any thoughts?

Jake Raby · 08-10-2009, 03:20 PM

Been there.. and I have a kit to do it.
I am testing it this weekend at a DE in two different cars.

I have gathered data that suggests the AOS does nothing to improve or impede performance, it was immeasurable on either of my dynos.

rob76turbo · 08-10-2009, 03:50 PM

Thanks Jake! PLEASE share the feedback you get. I have to replace my ASO very soon, but would rather do it with something like a catch can that I can check and can easily empty.

Cloudsurfer · 08-10-2009, 09:10 PM

Interesting....question is where to mount it? Did anyone ever get a decisive answer on whether the Motorsport AOS was do-able?

timothy · 08-11-2009, 06:04 AM

Quote:

Originally Posted by bmwm750

Did anyone ever get a decisive answer on whether the Motorsport AOS was do-able?

It most certainly is doable ... I have one.

Jake Raby · 08-11-2009, 06:06 AM

The rear trunk is where this one is mounted.. Its a full track car..

If it works as well on the track as it has in testing I'll figure out a better place to mount it on a street car.

jhandy · 08-11-2009, 07:30 AM

I looked up the catch can on the net and I can not find out what the advantage would be. Why would you want it? Does our car not have a AOS that does the same thing?
Just asking so I can learn.
James

Jake Raby · 08-11-2009, 07:55 AM

I had one track car with an AOS failure twice in the same day.. The second failure was a brand new AOS.

I have zero tolerance for something that fails and can dump oil on the track, or worse yet cause a fireball behind me like what I experienced last week on a test drive when the AOS went and the engine back fired and lit up all the oil vapors.

I'd only recommend AOS omission on track cars, it would not be legal in most areas for street cars due to emissions requirements, anyway...

A part failing once is OK, twice is not acceptable and anything more than that and its pure insanity as you are expecting a different outcome from doing the same thing over and over...

I have also experienced failed AOS units that caused low oil pressure as they allowed the intake charge to pull too much vacuum on the crankcase, thus pulling oil from the pick up tube and even getting so bad that main bearings squealed! When this happened there was ZERO smoke out the back of the car and the vacuum was so great that it sucked the front and rear seals further into the case and totally collapsed the oil filler tube.

It took us a day to figure out it was an AOS failure, so there are two different modes of failure of the AOS and this more rare, second type of failure can easily cause an engine failure due to oil starvation.. I am now exploring the possibilities of some oil starvation engine failures we have seen have actually been directly related to AOS failure and nothing else.

At leat with the AOS bypassed the chances of this occuring are zero as the function of the two systems are totally separated.

rob76turbo · 08-11-2009, 03:14 PM

I am with Jake on this one. If we can get rid of or bypass the AOS I am all for it. The issue may be the pollution controls. Since my car is street / track...

I would just to see an option other than replacing an AOS again and again.

Kirk · 08-12-2009, 11:15 AM

I've looked into this quite a bit. I have a Greddy oil catch can that was left over from a modded Subaru WRX that I used to own. I've looked and looked and measured and it will NOT fit anywhere reasonable in the Boxster engine compartment with the AOS in place. I had planned to install it after the AOS and before it vents into the intake. So this would basically be a backup if the AOS fails. The Greddy unit has a little sight glass type of tube on the side, so you will get a visible indication if oil is building up in it (as when the AOS fails).

The best mounting location that I found was in the rear trunk right next to the coolant reservoir/tank. Located there you would need to drill two holes in the rear trunk fire wall - one for the tube coming in and one going out to the intake right after the throttle body. Porsche uses some "special" tubes for the AOS and intake with funky connectors, but I think you can work around that with some hose clamps and regular tubing/hose.

In the end though I'm going to drop this project. I just bought a 914 that could use a catch can, so I'm going to put my old unit into service there as mounting and room in the engine compartment is a null issue. I'll just take my chances with the Boxster AOS for now...

Kirk

Kirk · 08-12-2009, 11:19 AM

Quote:

Originally Posted by rob76turbo

I am with Jake on this one. If we can get rid of or bypass the AOS I am all for it. The issue may be the pollution controls. Since my car is street / track...

I would just to see an option other than replacing an AOS again and again.

No pollution issue as far as I'm aware, as long as you vent the AOS back into the intake (just after the throttle body is where it goes stock). That way any fumes get burned and I "believe" the vacuum from the intake helps to draw the air through the AOS. What you can't do from a pollution standpoint (at least not in California) is vent the AOS to atmosphere. Some people do this with just a filter on the catch can outlet, similar to just putting a filter on your valve cover breather. That's a no-no.

Kirk

sd_boxster · 09-18-2009, 10:11 AM

Any news on this front? Jake, you tossed out this teaser: "Been there.. and I have a kit to do it. I am testing it this weekend at a DE in two different cars."

Any update on the kit (cost, degree of difficulty, thoughts about effectiveness, etc.)?

Thanks in advance!

Kirk · 09-18-2009, 10:25 AM

There's some discussion regarding this on the Boxster Spec board right now. I was at Thunderhill Raceway Park a couple weekends ago and watched a Boxster owner (not Boxster Spec, regular stock car) blow his AOS - big cloud of smoke, very cool.

I talked to him later in the pits and it was not his first AOS to go boom. I think the talk on the Boxster Spec board is leaning towards replacing the AOS entirely with a metal catch can. I think if you removed the stock AOS you could squeeze a Greddy can in there. I hadn't really looked at this, I had wanted to install my can after the OEM AOS, kind of as a backup. I think the route Jake is taking though is to replace the OEM AOS altogether, which makes a lot more sense.

Kirk

Jake Raby · 09-20-2009, 08:07 PM

Still in testing and will be for a good while. When creating such an outside the box part I must cover every base and attain data for "argument" purposes later when some know it all pops up to question why we are omitting what "Porsche designed".

Ken Cowin · 10-24-2009, 11:31 AM

What about the Motorsports version of the AOS (part number 996.107.926.00)? While this is quite a bit more expensive than the standard replacements I have read that it solves the issues with oil getting past the stock AOS on hard left hand turns on the track.

Gerardo de Kort · 12-15-2009, 06:42 PM

I've gone through about 3 AOS. I am currently running the Porsche Motorsport AOS but I fear it's not really doing the job. My boxster is boosted with a Turbowerx kit. The PM AOS was a genuine PITA to hook up and I probably didn't get it right. Any tips on how to install a catch can? What to plug up etc..

catmanluge · 12-16-2009, 05:04 AM

:dance: I have been using a catch can approach to solve my consistant AOS problems. It works well but I am finding that on the track the first quart of oil is picked up by the catch can after that without replacing the oil it works fine. As a result I am running one quart low..

My catch can is located in the engine compartment between the engine and the transmission. I also placed a drain tube that extends below the aluminium sheet panel with a shut off value for ease in draining the Catch Can.

2000 3.4 ltr Boxster