Subaru Legacy 2001 non-turbo PCV vent to atmosphere

[bradlington]

Anyone done a PCV delete vent to air on an ej25 .

thanks in advance.

[19bonestock88]

I haven’t got an EJ25(or any Subaru) but I have vented my PCV to atmosphere... I feel the main benefit is that there is less oil gunk in the TB...

However, the lack of oil vapors in the intake charge could slightly lessen knock (it’s been said that oil in the fuel lessens its octane rating)

[Daox]

Venting PCV to the atmosphere probably hurts mileage and power. Its likely not noticeable, but it is advantageous for your crankcase to run in vacuum. Those pistons are moving pretty quick, and they'll have to push even more air around if its not in a vacuum.

[19bonestock88]

So using a catch can would be a good compromise between the two?

[Daox]

I would imagine so.

[19bonestock88]

To eBay!

Seriously though, it hadn’t dawned on me that having a vacuum in then crankcase would reduce engine load...

Just a thought, but what about using the exhaust to pull a vacuum on the crankcase? Considered tapping a tube (venturi) into the exhaust after the sensors... it likely wouldn’t pass emissions though...

[me and my metro]

And it would probably smoke or just let unburnt oil run out the tailpipe.

[bradlington]

Racing guys use this principle of exhaust removing crank case gas and shoot it out the exhaust .

I need space in the engine so the only way I can get this space is to remove the current cone filter placed between the ABS break unit and firewall - place this directly onto throttle body .

The two pipes from either side of the boxer motor that go into the airbox-place these onto breather filters.
Not delete the pcv but rather take atmospheric air into pcv .
Whetehr the intake to the either side of the motor being a boxer motor is taken from airbox or via filter to atmosphere - I do not see any issue with this .

The pcv always sucks into towards the engine side and never the other way around- this is why it has a vacuum one direction valve.

Many delete the pcv due to the spent blow-by and parts of oil are recirculated into the engine for exhaust emissions.

If they designed engines to burn clean in the first place there would be no need to have a pcv except for venting crank pressure ,which in the old days was just vented to atmosphere and the road .

The only issue I have is the third connection to the airbox that from my study of the pcv circulation would be a failure backup in the event of the pcv valve failure .
To explain - this pipe has three connections- one from top of engine - one to pcv valve and the last has a smaller diameter to the air intake .
Seeing the reduced diameter and the skewed angle- my deduction is that under normal circumstances the vacuum from the manifold has a significantly higher vacuum than this path .
If anyone else has insight to this I would be interested in your interpretation .

regards
Bradley Glen

[cRiPpLe_rOoStEr]

Originally Posted by 19bonestock88

So using a catch can would be a good compromise between the two?

As long as it don't allow the crankcase vapors to go wide-open through the engine compartment, it's better. A friend who now lives in Portugal told me he has seen poorly-mantained cars catching fire because of that very same reason.

[me and my metro]

I understand your question better now.
Pcv systems under ideal conditions pull a slight vacuum on the crankcase. This is for many reasons, one is contain oil vapor emissions. Another and equally important is to remove moisture that can accumulate from normal combustion. Engines that do not vent properly crud up and sludge just ask Chrysler with their 3.5 v6. The solution was to increase pcv flow rates and the engines seem to be better now.
At full throttle or under boost conditions the engine has no vacuum. The engine also has high blowby rates during these conditions. This is when airflow reverses in the hoses in question. If your engine is in poor shape oil vapor or oil blows into the intake and the engine “oil farts”.
The newest cars include all airfow in the mass air calculations for fuel pulse width. Idle quality will change if you open the oil fill cap or just pull out the dipstick. Ford ecoboost vehicles can set a crankcase vent code if the o-ring seal on the dip stick is bad.

For your older Sube you can install small filters on each valve cover and eliminate all the other tubing. Leave the pcv where it is, it pulls off the center of the case.