Jay_

Can anyone help me out with advice on a breather mod I've been doing on my new age STI.... the attached is a photo of the PCV at the rear of the engine bay (turbo removed). I have vented pipe A to my catch can but pipe B is still running through to the underside of the throttle body. Question is, can I block off pipe B, remove the T piece althogether and then connect pipe A directly to the vent on the main block? This means there will be no venting back into the manifold, but will the car still run OK?



The other 2 vents I've run to the catch can are one head vent pipe on either side of the block. Basically there appears to be two similar sized 1/2" vent pipes coming off the block on each head. I've vented only the ones nearer the front of the engine... can the ones adjacent to them also be vented to the catch can? Sorry, would have posted a pic but forgot to take one today!

Cheers

Neilo

id like to know the answer to this one too as i had thought about putting one of those little K&N filters on pipe A....

Jay_

Neil... we've got small K&N style filters housed on the top of the catch cans... there's a pic on the Hants site under Technical. Mark's just posted a thread for the breather mod stage 1

marklemac

Boing. Someone must know the answer to this question.

andy97

iTrader: (1)

I have performed the same mod and left the pcv connected. I read alot of threads re the pcv, whether to keep it or remove it.

I decided to leave it connected as opinion said that oil vapour generally leaves the block under positive pressure, (hard driving). When using hard accelleration the block has positive pressure and the pcv is blocked off, so no/or very little oil vapour enters the inlet tract reducing the octane rating of the fuel when using full throttle.

I hope that make sense

Andy

millwrx

iTrader: (1)

yep thats what i have done too,

PICKLE

I have done exactly what you suggested Jay.

Removed the PCV, and blanked with suitable bolt/plug.
Blocked 'B' off.
Vented 'A' to Catch Tank, along with the rocker vents.

p1mark

Looks rather like my engine!

You will find that if you still keep pipe B connected to the PCV, you will not collect any resdue in the tank.

As Pickle says, plug the pipe, and the PCV hole up in the manifold and it works fine. RCM do it this way as well.

I have some drawings, will post them up later.

marklemac

Pickle, which ones are the rocker vents ?

coulty

The rocker vents are the plastic black pipe on top of each head. Run them seperately along with the crank breather to either atmosphere or a catch tank.

marklemac

Thanks. Looks like we've done those already. There are two pipe on each side, we have run the ones closest to the front of the engine to the can.

What does the pipe behind it do ?

p1mark

Here you go-

BEFORE


A is the inlet manifold
B is the inlet pipe
C is the turbo
D is the PCV valve
E is cam breather spigot on inlet pipe
F is cam breather pipe
G is crankcase vent tube
H is crankcase breather spigot on inlet pipe
I is crankcase breather pipe

the scissor points are where you need to cut the pipes leaving enough room to bung the pipes with a bolt or custom bung.







AFTER


A is a 1/4" BSP bung to replace the PCV valve
B is a bung for the cam breather spigot.
C are bungs for the crankcase breather spigot and the original pipe to the PVC
D is a T piece
E is the catch tank
F is a little filter

Jay_

Thanks Pickle . When you blocked off the PCV did this affect running of the car in any way?

PICKLE

Nope. All is fine.

As Mark says, I found that leaving the PCV valve on the Inlet manifold, I didn't get anything 'caught' in the Catch Tank.

Now, with the PCV removed, the Inlet Manifold is dry as a bone, and the Catch Tank collects all the condensation, and oil mist in a nice 'mayo goo'!!

You'll be suprised how quickly it fills up too!.


***Ps......The pipe 'F' in Marks diagram is the standard single pipe, which the rocker breathers have already been 'Tee'd' into. Just remove from Inlet Hose, and route to catch tank ***

Jay_

Great, thanks for the advice Pickle & Mark .... will block off the PCV as you suggest.

Back to my earlier query, now with pics of the left hand side of the engine with induction removed ... the other 2 vents I've run to the catch can are one head vent pipe on either side of the block. Basically there appears to be two similar sized 1/2" vent pipes coming off the block on each head. I've vented only the ones nearer the front of the engine (the clear/white braided hose)... can the ones adjacent to them also be vented to the catch can (stock black hose)? What is the black hose doing anyway!!?? Thanks

Jay_

Boing, can anyone help with the last query above, cheers

marklemac

Boing, can anyone confirm that we can 'vent' the 2nd pipe on the picture above. The one next to the clear pipe we have already vented.

marklemac

up

Northern Nick

iTrader: (1)

I'm just looking into this myself Mark, AFAIK you have got the right connection for your breather mod I haven't traced the other pipe 100% but it appears to just link left bank to right bank as a balance pipe, it will allow un-equal pressure between the two sides to balance to reduce over all pressure.

I recieved my Hyperflow catch can today and planning to do the job this weekend. Going to link striaght off the IC breather pipe so I have both cam cover breather on one pipe and then connect straight to the crank breather bypassing the PCV and the return to intake, blocking both off. Then for breating, I'm just going to run the return pipe out of the catch can through the plastice under tray to the floor.

I'd just like to add that the hyperflow catch can has 9mm fittings so I guess that 9mm must be capable of flowing enough air to cope with the engine breather system

Would also just like to add that you need to bend the lower A/C pipe with the valve on to allow the can to sit in its location and the upper A/C pipe to allow fitting of the breather pipes. The can needs to mounted on the second whole by only using one bolt so I slight modification required to allow it to miss the rear of the headlight. And isn't it just typical that the battery I have doesn't suit the clamp that comes with the catch can kit.

I'm fitting it to a 2002 STi but it does say on the instructions, 01+ WRX.

Still, modding cars is never straight forward is it....................... ever

fitsandy

Not being rude.

Well, Is it really that important to install a catch can to the already crowded engine bay ?

Why can we just attacha long hose to PCV and run it to the deep under chassis and vent the blowby fumes out like a mini exhaust.

Just add a paper filter to the breathing inlet of the engine cover. Thats it. Simple.

Why get into collecting the messy oil ... what for ?? You may reply directly to fitsandy at g mail dot com

Thanks.

Badbird

Does anyone vent engines to the exhaust system?? we do this a lot with big v8 drag race engines basicaly a slash cut tube inserted into the ehaust at an angle of about 45 degrees so the passage of the exhaust gasses creates a low presure area at the end of the tube which is connected too the crankcase vent and this positively draws the vapor ect from the motor into the ehaust, is there a reason not to do this?? bennifits i can see are no catch can no filters and positive purging of the crankcase??
when we got a bit more technical we fitted a small vacuum pump and pumped the cases clean this had a real good effect as there is a vacuum inside the cases, So no oil leaks, improved ring seal.and a neat instalation as it just needs one outlet from the motor all the others being blocked off

peter zippy reid

iTrader: (25)

Need to bump this see the breather t-piece my mate has ran pipe b to my catch can as crankcase breather is that wrong

FMJ

iTrader: (2)

Ideally don't bother with changing any of it. The PCV system is there for a reason and won't work properly with pipes removed.

But to answer your question if you just want to connect a catch can then just get rid of the two way connector and put one pipe straight to the catch can. It will then work as a catch can should. If he has put B to the can and not blocked the PCV valve you would have a vacuum leak. By just using B and leaving A connected to the intake pipe you will get oily air going both ways and it's not worth bothering with as your catch can will get some dirty air and some will go into the engine.

However if you do vent the crank case to a can you will loose the PCV system which IMO (many will argue otherwise) is a bad idea.

peter zippy reid

iTrader: (25)

I mean he has connected my can to b t-piece and took original b hose off and blocked A

peter zippy reid

iTrader: (25)

If he has done it wrong can anyone tell me where the breather is he should have ran from crankcase cheers

peter zippy reid

iTrader: (25)

Can some one tell me where pipe B used to be connected to as my mate used that connector for my can instead of pipe A

FMJ

iTrader: (2)

Has he blocked the PVC valve below the throttle and the hole in the intake pipe just before the turbo? If so then yes that will allow pressure to go to the can... Not a setup I would recommend because I don't agree with the PCV delete but it's in line with what other people do.

peter zippy reid

iTrader: (25)

He has left the connector attached to block but blocked hose A and the hole in the intake hose and connected my catch can breather port to connector B

peter zippy reid

iTrader: (25)

Where is the pcv is it the pic in the op first post

FMJ

iTrader: (2)

Ok the pic we are looking at may be confusing things. That pic is not how the pipes go as standard. Pipe A would usually go right and attach to the exposed silver coloured nipple on the red silicone intake hose. But in that pic it's been rerouted left.

Pipe B in that pic looks as it does standard and heads left and connects to the PCV which is a metal valve beneath the throttle.

This pic shows which way the hoses go as standard

As long as both the PCV and the nipple on the inlet are plugged so they don't leak then that will be fine. Then the crank vent to the can. Then the can vented to atmosphere is what most people do.

This pic shows a PCV valve directly below the throttle

However IMO PCV is a good thing and should be kept. It should not be ditched and rerouted to fit a can. But that's just my opinion.