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Old 05-31-2017, 06:24 PM   #1
pcampbell
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Default Engine breathers on supercharged EJ253

Can anyone provide any advice on how to handle breathers and PCV on my supercharged EJ253?

1) Cap the PCV. Vent rocker breathers to catch can and then to atmosphere?
2) Leave PCV alone. Vent rocker breathers to catch can and then to atmosphere? PCV will draw unmetered air in at idle or whenever else the PCV is valve open (pretty sure I'll be boosting any time above idle?)
3) Run breathers (and PCV?) to catch can and then back into the pre-Supercharger side of the intake?
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Last edited by pcampbell; 05-31-2017 at 08:10 PM.
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Old 05-31-2017, 07:54 PM   #2
vicious_fishes
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The manifold to crankcase has a one way valve so that's fine, but the vertical exit of the Y pipe coming out of the crankcase needs vacuum or VTA. The same goes for the head breathers.

It's very common to T the heads together and then have two lines running either into catch cans or into the SC's inlet if you want to keep it emissions legal.
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Old 05-31-2017, 08:17 PM   #3
pcampbell
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Quote:
Originally Posted by vicious_fishes View Post
The manifold to crankcase has a one way valve so that's fine, but the vertical exit of the Y pipe coming out of the crankcase needs vacuum or VTA. The same goes for the head breathers.

It's very common to T the heads together and then have two lines running either into catch cans or into the SC's inlet if you want to keep it emissions legal.
Would you be able to point me towards where to find this "vertical exit of the Y pipe coming out of the crankcase?" Where does that line go? I only know of 2 rocker breathers going back into my intake box (in the N/A form) and I see the PCV hose going into the intake manifold.

VTA , I am OK with it but just want to make sure it won't cause problems. I've read of concerns of condensation in the hoses freezing, then causing a blockage. Or causing a vacuum leak when the PCV is actually working (because the PCV will draw air in through those breathers). In my case I don't think the PCV would actually open much at all though - maybe a little bit at idle, otherwise it'd be under boost and closed.

My issue with going back into the intake post MAF/pre-SC is
1) Oily air into the SC and intercooler
2) Is it possible this could actually create too much vacuum at high boost/RPM?

Thanks!!

Last edited by pcampbell; 05-31-2017 at 08:25 PM.
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Old 05-31-2017, 08:31 PM   #4
vicious_fishes
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Quote:
Originally Posted by pcampbell View Post
Would you be able to point me towards where to find this "vertical exit of the Y pipe coming out of the crankcase?" Where does that line go? I only know of 2 rocker breathers going back into my intake box (in the N/A form) and I see the PCV hose going into the intake manifold.

VTA , I am OK with it but just want to make sure it won't cause problems. I've read of concerns of condensation in the hoses freezing, then causing a blockage. Or causing a vacuum leak when the PCV is actually working (because the PCV will draw air in through those breathers). In my case I don't think the PCV would actually open much at all though - maybe a little bit at idle, otherwise it'd be under boost and closed.

My issue with going back into the intake post MAF/pre-SC is
1) Oily air into the SC and intercooler
2) Is it possible this could actually create too much vacuum at high boost/RPM?

Thanks!!



Those two hoses circled Y together and then into the crankcase. The intake manifold has a one way valve but the one into the airbox does not. You need to either draw vac or vent it to atmosphere.

The more vac the better with RPM, remember the harder the engine is spinning the more pressure it's under/more blowby there will be.

I've *never* heard of blockages from freezing in PCV lines, ever. If the lines did get blocked, the worst that would happen is the pressure would just pop them off the breathers anyway.
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Old 06-01-2017, 12:15 PM   #5
pcampbell
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Sorry, is there a picture or hint on where this Y is located. I don't see it but may not be looking in the right spot. Could it be that the NA EJ253 doesn't have a crankcase breather, only a PCV and the rocker breathers?

What I've done so far is re-route the rocker breathers to a catch can. Joined together via a Y. I'm not boosted yet, just trying to get everything all laid out correctly. The intake box is replaced by an IC, so no holes to plug there.



This is from the service manual:

Quote:
3. Crankcase Emission Control System
z The positive crankcase ventilation (PCV) system prevents air pollution that will be caused by
blow-by gas being emitted from the crankcase. The system consists of a sealed oil filler cap, rocker
covers with fresh air inlet, connecting hoses, a PCV valve and an air intake duct.
z In a part-throttle condition, the blow-by gas in the crankcase flows into the intake manifold through
the connecting hose of crankcase and PCV valve by the strong vacuum created in the intake manifold. Under this condition, fresh air is introduced into the crankcase through the connecting hose of
the rocker cover.
z In a wide-open-throttle condition, a part of blow-by gas flows into the air intake duct through the
connecting hose and is drawn into the throttle chamber, because under this is condition, the intake
manifold vacuum is not strong enough to introduce through the PCV valve all blow-by gases that
increase in the amount with engine speed.

Last edited by pcampbell; 06-01-2017 at 01:00 PM.
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Old 06-03-2017, 04:16 PM   #6
pcampbell
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Quote:
Originally Posted by vicious_fishes View Post



Those two hoses circled Y together and then into the crankcase. The intake manifold has a one way valve but the one into the airbox does not. You need to either draw vac or vent it to atmosphere.

The more vac the better with RPM, remember the harder the engine is spinning the more pressure it's under/more blowby there will be.

I've *never* heard of blockages from freezing in PCV lines, ever. If the lines did get blocked, the worst that would happen is the pressure would just pop them off the breathers anyway.
Ah ok, my vehicle doesn't have that. Mine only has 2 rocker breathers going into the air box and the PCV. I think i should be ok with just venting the rocker breathers and leaving the PCV alone.
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Old 07-12-2017, 06:16 PM   #7
v2rocket_aka944
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...depends what kind of SC.

roots/positive displacement - order should be:
air filter > MAF > fresh air line to valve cover > throttle plate > PCV from crank case > blower

centrifugal type:
air filter > MAF > fresh air line to valve cover > blower > throttle plate > PCV from crank case (in manifold)
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Old 07-12-2017, 06:46 PM   #8
pcampbell
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This is what I ended up doing

air filter -> maf -> BPV return / engine breathers (come in at the same spot) -> SC -> TB

I left the stock PCV alone.
I could see some argument for disconnecting it, plugging the manifold, and hooking it up to the suction side of the supercharger. But for now I think it's fine.
The breathers should allow blowby to escape.

Last edited by pcampbell; 07-12-2017 at 07:04 PM.
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Old 07-13-2017, 03:48 PM   #9
vicious_fishes
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If your car has it you would have had to disconnect it from the airbox.

Post up a picture.
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Old 07-13-2017, 05:03 PM   #10
pcampbell
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For whatever reason my 05 is different.
There's only 2 lines going to the factory airbox, they are the rocker cover breathers 1 each head. Those will now get sucked into the impeller side of the supercharger. I got rid of the catch can.


Then there is the PCV which only goes from the crankcase directly to the intake manifold. Nothing to the airbox. I'm leaving that alone for now. If needed, can also have it join up to the intake side of supercharger and block off the port on the intake manifold.
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Old 07-18-2017, 02:41 AM   #11
vicious_fishes
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Correct. But you need to make sure that as it presently sits it has the one way valve in the manifold.
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Old 07-24-2017, 03:09 PM   #12
pcampbell
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Just the PCV itself which should close under boost.
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Old 08-05-2017, 11:31 AM   #13
pcampbell
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OK so I have this hooked up this way right now:
Rocker breathers go in before supercharger all the time (light vacuum).
PCV is stock (goes to intake manifold and is closed under boost).

I think I need to figure out how to make it so that the PCV goes to the intake manifold under high vacuum (current setup) BUT will instead go to pre-supercharger when under boost/backfire. Can anyone recommend a way to do this?

The reason I want to do this is to allow for another way for blowby to escape while under boost. Also... this is how the factory turbos are setup(I think).
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