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Air Oil Separator ? Worth fitting ?

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After reading quite a lot about the potential detonation caused by the oil contamination in the air/through inter cooler I'm seriously considering fitting an AOS.

Currently looking at Grimmspeed, Perrin or ITG. Best for the price I think is the Perrin.

Does anybody have a feedback or experience on these, particularly with the track use in mind.

Cheers

Darren

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I read that the grimmspeed one isn't brilliant for track wor, the perrin one looks good and has good reviews but it's pricy,

I'm in the process of adding mishimoto cans to my set up

  • Author

Cheers stants, I've seen the catch cans, but preferred not having to empty them and it being a mainly automatic process. These cars should really have them fitted as standard.

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The cheap catch vta can I bought does the job but if I had the time and money I'd have fitted one that returns to sump .

As I have to empty mine 4 time's a year and I take it off completely and rinse it out every spring .

Deleting the oil breathing system is a worth while mod imo especially if you're looking at doing track days, when it will be breathing heavy .

I'd definitely consider a baffled sump and fuel swirl pot if you do intend on doing a quite a few track days.

As this will reduce fuel "slosh" and oil surge/starvation when cornering heavy .

If it's not broke .....upgrade it 😊

Look at the missimoto kits too very good peace of kit

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  • Author

Track days will be to a minimum this year, so maybe a couple :-)

If I do start doing more next year and when the warranty expires (!!!) I will certainly get a baffled sump and probably swap the OEM pick up at the same time.

I've not seen the Missimoto ones yet so I'll look into that brand.

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I have the two port for the intake side of things, although not as cheap as others it's well made billet ally and the fit and finish are spot on

I will be considering the mishimoto kit when returning to boosted life - yes you pay a little more but they have a full kit for the hatch, brackets etc

The mishimoto one is two billet cans with built in filters. Check out there uk site all there stuff comes with a lifetime warranty too

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Only for newage though, sod all available for classics,luckily the id of the hose appears to be the same as subaru use so I just got myself 6' or oil line hose and fabricated a bracket just need the time to take the ic off and install [emoji16]

  • 1 month later...

  • Author

So have much reading of reviews, I ended up ordering the Perrin one and should be here next week. Wasn't cheap but wanted to keep PCV and after seeing the amount of oil in the inter cooler I wasn't a happy bunny [emoji848]. Doesn't look the simplest of installs but plenty of US based install videos so hopefully is similar....

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BTW anyone fitted a Perrin AOS on a 2014/2015 WRX STi ???

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  • 2 weeks later...
  • Author

Fitting day today, wish me luck [emoji53] didn't think about having to relocate it due to RHD versus LHD and the master brake cylinder.... doh.... Could be fun and not 100% confident at this point in supplied tube/pipe length. Going to do a basic fit and tube run without any real modification and if I need more stuff all I need to do is refit the TMIC then and pop to Halfords or purchase during the week.

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That the one with the coolant line feed into the bottom ?

Once I got my head round the plumbing it was fairly simple with the 2 port, hope Yours is too [emoji3]

  • Author

Well that didn't go as planned. Got intercooler taken off (took ages as I didn't realise I had to take a bracket off on right had side to slide out), got a reasonable mounting position and got crank vent and oil lines in. Routed the pipes for the coolant and although 'just' enough pipework, it was fine. Then on to the left and right vents which needed a run round the back of the intercooler for the left one and then realised that this run took up 3/4 of the tubing supplied and also that due to the AOS mount ing position, the tubing wouldn't bend tight enough to connect to the AOS.... DAMM. So had to rebuild the engine back to how I found 5 hours earlier. Now need to get some more 1/2" tubing and 2 more right angle connectors for the AOS. For anybody else doing this get some pipe cutters (made my life much easier) and some Subaru coolant to top up after your fitted the coolant hoses. I also bought 1 hose clamp, but should have bought 2 so i could clamp incoming hose and outgoing hose from throttle body (?) to save loosing coolant. First time I've tried anything his big on a car, so even though it didn't happen, quite happy I got this far and rebuilt everything without a problem.... :-)

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Tbh I probably enjoy moding more when I've got to make something fit rather than just bolting something on [emoji15]

But I do like a challenge [emoji4]

I've found autosiliconehoses or ash to be fairly cheap and good quality for ally and silicone pipework [emoji6]

If it's not broke .....upgrade it 😊

  • Author

Thanks savage, just about to order the bits now and then have ago again this weekend. Should be much quicker now I know what I'm doing with inter cooler and most of the pipe routing [emoji39]

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In preparation for next attempt, can anybody confirm where the PCV valve is on the 2014 onwards STI. Doesn't seem to be in same point as previous generation. Is it screwed into the manifold? Or somewhere else along the chain?

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Not really but from what I've seen over on us sites the my14 foz sits in a y pipe coming off the top of the crankcase sort of pokes out the side of the tube coming from it,

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  • Author

Yeah that's where I hoped it would be, didn't see it, but will double check the y pipe fitting again on next attempt :-) thanks stants.

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  • Author

So they changed it on the 2014 onwards STi and it's now screwed directly into the manifold. It's also a weird size and bigger than the rest of the tubing (1/2" or 13mm) and is 5/8" or 16mm in size. So the short version is the Perrin parts don't fit perfectly on latest STi, but I have found a company who do 5/8 to 1/2 reducer to allow me leave the PCV in place, use the standard Subaru tubing and then link it into the Perrin kit. For people's future reference the company is called Advanced Fluid Solutions. 3rd time lucky next weekend :-)

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  • Author

Forgot to say as well, I've had to go to a single valve cover vent connection on the AOS rather than have two separate lines as I can't get two right angle fittings on the Perrin AOS now it's mounted on the right hand side of the engine bay. So I'm going to do the alternative connection of single AOS vent case connection and the Y it off to the two engine vent case connections. Also worth noting that if you need Subaru coolant I couldn't find it easily to order online and ended up getting it from local dealer for approx. £16.

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  • 4 months later...
  • Author

Quick update - pulled the BOV and a few pipes last weekend to find them dry as a bone, even inside the inter cooler which had a pool of oil before. Well impressed with the improvement, so seems to be well worth doing.

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