PCV replacement and catch can installation

[Shakedownsavvy]

Alright guys so I'm about to change the pcv assembly on my 2005 Legacy GT and while I'm in there I'm going to throw on a catch can. Now I've done about 3 nights of searching this forum and nasioc and any other subaru forum about catch can installs and none are very clear with pictures. I'm putting it in line for the crankcase and my question is about where to plumb it. Do I go straight from the hose coming from the PCV to the intake (hose with "sensor" connector) to the intake of the catch can then the outlet of the catch can back to the hose with the connector (pre-"sensor"connector)? thanks in advance.

[quick4dr]

just do a AOS from IAG or Perrin, or Crawford... catch can is old news

[NSFW]

There's a monster thread about this at IWSTI:

 

http://www.iwsti.com/forums/2-5-liter-litre-factory-motor/146699-official-sti-engine-venting-o-separators-catch-cans-thread.html

 

Great diagrams in the first post.

[Sgt.Gator]

As with most mods "it depends". There are endless versions of catch cans and AOS installs. Some are for pure street cars that have a lot of blow by on loosely built forged motors. Some are for track day cars that never go more than 20-25 minutes on a track. And some are for full race car applications. I have my opinions, YMMV, so here's my $.02:

 

1) Street Car with oem block and typical stage 1-2 build. Stay OEM PCV. It works fine.

 

2) Track car doing HPDE events of 25 minutes on an OEM block stay oem PCV. Check your inlet tract for excessive oil. (From MAF to Turbo, and in the TMIC or FMIC piping). If you have a lot of oil check over your PCV system closely for issues, replace PCV valve, if still a lot of oil go to #3.

 

3) Track car doing HPDE on built forged block and/or you are having issues with oil in your intake tract, consider an AOS. I've looked at all of them. Today I would go with the Perrin.

 

4) Race car, as in dedicated to nothing but racing. Perrin AOS or Dry Sump.

 

In 1-3 of the above if you don't have a bunch of oil in your intake tract or tmic/fmic piping stay with oem pcv. If #4 I personally skip straight to dry sump for all my race cars now, but I recognize that's very expensive.

 

Remember an improperly configured catch can/AOS can be worse than an oem PCV! I think a Crawford AOS that had a pinched block feedback line contributed to my Spec B spun bearing, it at least caused a ton of oil in my intake tract.

 

And the consensus from numerous folks is to stay away from the Grimmspeed aos that goes in your oil fill tube if you are tracking your car. It may be ok on the street, but on a race track it's not.

[Shakedownsavvy]

As with most mods "it depends". There are endless versions of catch cans and AOS installs. Some are for pure street cars that have a lot of blow by on loosely built forged motors. Some are for track day cars that never go more than 20-25 minutes on a track. And some are for full race car applications. I have my opinions, YMMV, so here's my $.02:

 

1) Street Car with oem block and typical stage 1-2 build. Stay OEM PCV. It works fine.

 

2) Track car doing HPDE events of 25 minutes on an OEM block stay oem PCV. Check your inlet tract for excessive oil. (From MAF to Turbo, and in the TMIC or FMIC piping). If you have a lot of oil check over your PCV system closely for issues, replace PCV valve, if still a lot of oil go to #3.

 

3) Track car doing HPDE on built forged block and/or you are having issues with oil in your intake tract, consider an AOS. I've looked at all of them. Today I would go with the Perrin.

 

4) Race car, as in dedicated to nothing but racing. Perrin AOS or Dry Sump.

 

In 1-3 of the above if you don't have a bunch of oil in your intake tract or tmic/fmic piping stay with oem pcv. If #4 I personally skip straight to dry sump for all my race cars now, but I recognize that's very expensive.

 

Remember an improperly configured catch can/AOS can be worse than an oem PCV! I think a Crawford AOS that had a pinched block feedback line contributed to my Spec B spun bearing, it at least caused a ton of oil in my intake tract.

 

And the consensus from numerous folks is to stay away from the Grimmspeed aos that goes in your oil fill tube if you are tracking your car. It may be ok on the street, but on a race track it's not.

 

 

 

Thanks for the info! I actually just went ahead today and changed the pcv valve and decided not to put on the catch can. While I was in there I noticed a lot of oil around the hose going into the inlet pre turbo. It looks like the line came from the valve cover breathers maybe on a line that ran under the tmic. Not sure where it's coming from.