For some time now the general consensus has been that ditching the oem PCV system is the way to go to prevent oil vapours entering the intake and lowering the effective octain of mixture. This is something I'm keen to do as ,due to this, I'm suffering some transitional det at mid rev range WOT.

However, having done a lot of background searching on this mod, IMHO, there still seems to be of a grey area..!

Specifically, as the heads (and crankcase iirc) 'breath' in as well as out, what are the implications of unfiltered air (catch tank or direct VTA) entering the engine..? Some advocate the use of a K&N style crankcase filter to prevent this happening, but these quickly become clogged with oil redering them useless (as well as dripping all over your drive..!)

Also, given that the PCV system helps scavenging from crankcase, does removing it effect the oil return to the sump..?

Forgive me for posting these questions, I'm just after confirmation before doing this to my 05..

Jason

 

???

 

I think a more pertinent question for newage cars is where is the space to fit a single catch tank that can be accessed easily to empty/ inspect it.
I have a tank gathering dust in the garage as I still can't anywhere to put it yet.
From web info, I was under the impression that it was simpler to feed the catch tank outlets back to the inlet track to replicate the OEM system.
Moving to two small tanks to keep separate crank and head systems avoided any cross feeding of boosted/vacuum air flows and may allow easier space allocation.

Nick

 

Good point m8..!

I was wondering this exact thing myself as there is very little room. Did also think about using two systems, it's just finding the bloody space..!

Cheers..

 

judging by the amount of oil in my catch can it will take 4 years to fill. just got the crankcase connected. got an additional pcv valve in the rocker circuit to allow air in but not oil out.
ken

 

On my classic i have vented the block breather to a catch can but have put a one way valve into the head return pipe and left it plumbed back into the inlet which means it can still suck air into the engine under vacume situations but can't blow and oil back out under boost.

Dan.

 

^^^^^

Do you guys vent you cans to atmosphere or back into air inlet duct..?

Also, have you checked your IC/pipework since doing this mods. Has it prevented any oil mist entering intake..?

Jeese, there are so many differently opinions about plumbing this mod..!

 

Err my catch can has no lid so i guess VTA

 

Once vented there will be no oil in the inlet, turbo, i/c or TB, unless the turbo is leaking.

I vent my catch can to atmos (the road) via a pipe. The pipe will be extended to the rear of the car eventually.

F

 

I am very close to doing this mod to my Classic WRX but am also a bit confused!

As I see it from what has been said, there are still a couple of configurations...

1. Run both head breathers into a 'T' and then plumb them into one port, then plumb the crankcase breather into the other port. Once complete you can either a) vent the can to atmosphere using a small filter/breather or b) vent the can back to the inlet system as OE. (This requires a can with three ports, two inlet and one outlet)

2. Use two seperate cans, one for both head breathers and the other for the crankcase breather. Then as before either vent to atmosphere or back into the inlet.

Just to make things a bit more confusing, if venting back into the inlet you can also add a PCV valve to make certain that air can get in but no oil back out...?



Personally I can't see any of the above configurations harming anything as they are still an improvement on the original setup (for the purpose of removing blow by gasses/oil). Except maybe the need for the heads & crankcase to breath in as well as out... as mentioned by jasonius, not sure about that point??

 

Butty

I have put my catch can on the rear bulkhead where the TMIC used to be...........the perfect excuse to go the FMIC route.....LOL

Midlife.....

 

That's one (expensive) way of getting around the problem

Nick

 

looks like Danny and myself have similar set ups.
I disconected rubber elbow (by the turbo) from inlet pipe and turned it through 180 degrees and used a straight plastic connector to join pipe to catch can. then another pipe from catch can runs under the car to vent out.
I then blanked off the hole in the inlet pipe.
the rocker cover pipe goes to inlet pipe nearer the front of the car I installed a one way valve in that hose. no oil present in TB or IC since doing this.
ken

 

From what I've been told the heads need to breath in and out, so one way valves are not advisable..!

 

Butty

The FMIC was a "replacement radiator under warranty" as I told the wife !!

you dont have a rear strut brace for the bugeye in your garage by any chance ??

Shaun

 

ahh one of those bars that strenghen the boot to allow more shopping

 

Hmm, thats one for the book.

Sorry - the garage stock is a bit bare at the moment.

Nick

 

why is this Jason? did they explain it as im just about to put a PCV in mine and you have thrown a curve ball now .

Surely the pressure in the crankcase and heads will be equal?

 

was advised to put pcv valve in rocker circuit like I've mentioned by a very experienced mapper. thats good enough for me.
ken

 

Bob Rawle recently advised me against a one way valve as the heads breath in and out..

I know Bob has used an extra PCV valve in the past, but that was 3-4 years ago..! Seems that things have changed since then..?

From what I've recently found out (with many, many enquiries to some very experienced people ) it would seem that venting direct to atmos. (via a catch can to keep an eye on amount of oil) is the recommended way to go. One way valves are not needed as re-circulation of blow by gases is not a problem. Neither are filters as the unfiltered air that may enter the engine is insignificant..! Apparently

This appears to be one of those mods that's very easily over complicated/analyzed (sp?)..!

 

jason are u coming to cov meet on sunday?
ken

 

Ahh, what time & where..?

Didn't realise there was one..

 

its at the royal oak baginton 1 pm
A45 follow signs for cov airport but turn right at mini island just off A45 up to next mini island turn left. pub on the left