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2007 FXT Sport M5
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78 Posts
Discussion Starter #1
I see a lot of info on the Grimmspeed AOS on other forums, the principle is interesting, don't waste oil by burning it and keep you air intake clean and octane at the level you pay for. The only thing I was not interested in was the $300+ US pricetag. I thought I would slap something together myself. After about 15 minutes at Princess Auto and 45 minutes of my time fabricating I came up with the following:









The principle is simple, dirty air from PCV goes down the long nipple into the filler neck and the oil particles condensate and drop back to the crankcase -> the clean continues back into the intake through the nipple that is mounted flush with the filler cap. The space between the two nipples and the screen would allow for enough time to condensate. This system does the same as the machined one, just does not look as pretty. The quick connects were put on to allow for easy access, it would be a pain to have to unscrew clamps just to remove the oilcap. This is a first try only, not looking for ghetto-fab comments. What do you guys think?

Pete
 

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The Sub kit guy
2005 Forester X & XT VF39
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13,008 Posts
Height might be an issue. I believe there isn't much clearance above the cap. Other than that I'd love to see a "budget" option!
 

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2007 FXT Sport M5
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78 Posts
Discussion Starter #4
There are no check valves other than the PCV valve in place, I do not believe the Grimmspeed or similar products have any check valves included in their system. The oil condensates and the clean air moves through the intake system. Are you concerned the engine will run lean?
 

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2004 Forester XT
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78 Posts
I might be completely wrong, but I thought that the oil system was pressurized, so where is the crank vent gas going to go while the engine is running? I have not ran my Subie with the oil cap off, yet, but when it happened to my beemer it made a huge mess. I do not know the subie engine as well as a diesel engine but we plumb the oil catches to the sump side through a check valve... and the gasses pass through into the turbo inlet... I don't know, but thats why I read up on these forums... enlighten me Obie Wan.
 

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Official sf.org decal guy
2006 FXT
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12,367 Posts
I might be completely wrong, but I thought that the oil system was pressurized, so where is the crank vent gas going to go while the engine is running? I have not ran my Subie with the oil cap off, yet, but when it happened to my beemer it made a huge mess. I do not know the subie engine as well as a diesel engine but we plumb the oil catches to the sump side through a check valve... and the gasses pass through into the turbo inlet... I don't know, but thats why I read up on these forums... enlighten me Obie Wan.
If that were true than wouldn't you have issues with the Grimmspeed AOS?

Looks like a sweet idea. I'm interested to see how it turns out.
 

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2004 Forester XT '06 STi 6MT
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707 Posts
i wonder if this could be done with maybe an aftermarket oil cap and some -AN weld ons?
 

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2007 FXT Sport M5
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78 Posts
Discussion Starter #8
The filler neck is not pressurized or you would have to fill it to the top. The oil system after the pump is pressurized, your BMW likely had the cap on the valve cover, and there is oil spray there to keep the camshafts and mechanicals lubricated. I think the key is to have enough space and some kind of screen to collect oil vapours and allow them to condensate and drop back down the filler neck. I don’t have much of a concern with water and other similar contaminants as they originate from the crankcase regardless. There’s more than one road that leads to Rome, I guess you could make a lot of different configurations. From looking at the drawings for the Grimm speed unit the vapours appears to just drop into the filler neck and over pressure gets released through the opening next to it and through a second groove located in the AOS. I do not think this unit would be much taller than the Grimspeed or similar units when installed as they get installed under and raise the oil cap. This fabrication just has a brass 90 degree elbow.

Pete
 

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2004 Forester XT '06 STi 6MT
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707 Posts
so from the pics it looks like the screen mounts flush to the long nipple? have you thought of maybe filling the space in between the screen and the cap with some sort of stainless mesh? to me that would make more sense in allowing only air to escape.

my only other concern is how well it will all be sealed after modifying the plastic cap. but it looks like you epoxied the fittings in so it should be good.

interested in how this works out for you.

edit: you are installing this like the prova kit correct?
 

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2007 FXT Sport M5
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78 Posts
Discussion Starter #12
^^^^

Love your products, if you want to trade let me know. :D I know a lot of R&D goes into your products and it is not cheap to produce machine items. The Dutch in me just squeeks when I see the price tag + shipping + duty + tax +UP(S) the donkey fees. I had an extra oilcap and just had to try something as I wanted an AOS to keep the intake clean. For 1 hour of time and $25 and a first try I don't think it's half bad.

Pete
 

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04 Forester X, MT
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1,039 Posts
Nice DIY Air/Oil Separator! :cool:

I have a Prova Air/Oil Separator on my '03 X, but I just can't seem to part with $400+ (todays going price!) to install one in my '07 FSXT! :icon_eek:

Bobby...

My MODding Journal
Surely there is something out there cheaper than this that doesn't look as nice?!

Does it really keep intake cleaner enough to be worth it?
 

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2007 FXT Sport M5
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78 Posts
Discussion Starter #15
^^^^^^^^
Grimmspeed has one and I think SUBTLE is in the process of making something similar. Those units would cost less than the PROVA but still too much for my cheap Dutch ***. I do love the look of the machined pieces, but at the same time I enjoy Frankensteining something together that as far as I can make out (correct me if I'm wrong) does the same thing, not saying that these quality machined pieces made by reputable companies are not worth every $$$$$.
 

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Ah crap.. I'm back with my 05 XS
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8,294 Posts
Only thing left to do now is slap on some clear tubing and put that baby through some trials. Where Grimmspeed and Prova differ is that the Prova unit doesn't deal with the PCV system.
 

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Administrator
2007 Forester Sports XT 4EAT
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39,823 Posts
^^^^^^^^
Grimmspeed has one and I think SUBTLE is in the process of making something similar. Those units would cost less than the PROVA but still too much for my cheap Dutch ***. I do love the look of the machined pieces, but at the same time I enjoy Frankensteining something together that as far as I can make out (correct me if I'm wrong) does the same thing, not saying that these quality machined pieces made by reputable companies are not worth every $$$$$.
IMO The PROVA piece has a nice design, where the OEM/factory cap is retained. It is way over priced! If it were half the price, I'd get one for my '07. I love the one in my '03 X! :cool:

Only thing left to do now is slap on some clear tubing and put that baby through some trials. Where Grimmspeed and Prova differ is that the Prova unit doesn't deal with the PCV system.
As an option, you can also route the PVC gases thru the PROVA... like how it's done when you add some aftermarket turbo inlet hoses. :wink:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 

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2004 XT
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58 Posts
Sorry to bring an old thread to the top, but I got a question.
I think I'm missing something with those AOS on stock oil cap. How it can work? Cause the stock pcv line contain oil vapor(that crap the inside of the intake), so how putting it on the top of the oil cap can change something. From what I saw on this diagram, the baffle are on the 'in' section, not the 'out' section. So their will be vapor coming out of the cap? No? And if their still oil vapor from the oil neck, why condense the oil coming from other part of the motor?

Someone can light me? :confused:
 
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