Subaru Legacy 2001 non-turbo PCV vent to atmosphere
 

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

thanks in advance.

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)

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.

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

I would imagine so.

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...

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

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

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.

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.

Current:
Engine side: Airbox Side

Crankcase left===============(XXX)==Airfilter left side


PCV Valve =====================Top Engine
. "
. "
. "--------(YYY)-Small pipe to Arfilter box near center(My assumption is PCV failover protection)


Crankcase Right=============(ZZZ)=== Airfilter Right Side
.................................................. .................................................. ....
New :
Engine side: Airbox Removed
Crankcase left===============Breather filter left


PCV Valve =====================Top Engine
."
. "
. "---------Use for injection of Water or fuel vapor or HHO


Crankcase Right=============Breather filter Right

I hope the old style of drawing line diagram represents what mu intentions are .

Once I have this I can remove the whole airbox and only use the Cargo large Cone direct onto throttle body.Previous placement of the cone filter directly on throttle body resulted in some additional noise when sudden acceleration - sucking sound - but plan to place a metal shield over it to make use of majority of air to be pulled in from hot engine .

The "failover protection " PCV connection , which has lower vacuum than the main PCV (a proportional relationship to main pcv flow) can then be used for whatever combination I want to inject be it HHO-water Fuel vapor , mist or perhaps all of the mentioned .
Once my new exhaust is on next week and the wideband AFR meter installed I would be able then have a good way of accounting for various changes being made .

One up on the Subaru design - I see many other makes of vehicles do not have this PCV failover design .

Updated: Had my old exhaust replaced with 50mm stainless steel with one small Cowley box mid way and One Cowley straight through muffler .
Sound is awesome - like my previous impreza.Only catch is the fitment center did not have the tools to remove the front CAT and re-fit the O2 sensor-- I think I scared the hell oout of the service manager when I requested the additional wideband bung to be mounted between 10 and 30 degree max from vertical.
Today I went to see a well known performance specialist, whom builds and races vehicles and I saw some of his welding work - really precision stuff.Tomorrow I have my vehicle booked in and the necessary small 50mm bend has been acquired to replace the front cat . This should end my exhaust and next phase would be wiring up the wideband cables and gauge to monitor for a few days before venturing into next phase.

I have just been re-reading over the older posts fom Aaron Murukami where he modified his Subaru PCV and he indeed blocked his actual PCV - allowed the back up - failover (my assumption )to vent from airbox. .The question would be , will have to place a vacuum guage on these three pipes to and from motor to see if there is any pos pressure inherently - if not how would the system work if there is no high pressure on one side of the system and no low pressure - this would mean gases would not flow .
Going to have to ponder over this one again .

I wouldn't expect it to become an issue. Remember the Citroën 2CV? It generated vacuum inside the crankcase while the engine was running. OK, I know it's a whole different animal, but some vacuum might not harm efficiency at all. Maybe decreasing resistence against the turns of the crankshaft would even become somewhat beneficial. Not sure on that though, but seems worth trying.

On our race engines we would just provide enough vent area, no pcv. The engine was run wide open then closed throttle into the corners then back to wide open lap after lap. If you are going to run your car this way don’t bother with a pcv they only work at cruise and idle. Boats don’t have pcv valves they just vent both valve covers.

Thank you for the information .Last night I had a brief search for Subaru EJ series being used in the aeronautical side.
I drive slower than my mother-in-law(so the reports from my boys are given as ) and certainly no speedster .
I am sure they do not use PCV or vent to air but if anyone has more ideas or references I would appreciate it .
Update - just returned from a motor rading expert and had the CAT deleted with two bungs - one for narrow band original O2 and a second one for my AFR WBO2 sensor - hopefully by weekend I will have the gauge in and can satrt taking more notes with each change.

I second the exhaust connected pcv system. For road coursing mustangs which stay in gear under decel at up to 8000 rpm on the new 2011+ 5.0 motors (modified intake and operating range) the best way to keep a vaccum on the heads for good oiling and not drink oil is to connect up a exhaust manifold connected pcv system and its really low maintenance since there is no emptying of the can. Also, another good option os the old turbo volvo catch cans. The turbo volvo catch cans are baffled and allow the engine oil to settle at the bottom and have a return line at the bottom which is connected to a return line to the oil pan. Typically venting to atmosphere is a no no unless you're not worried about engine longevity or are not worried about catch can maintenance.

So this is the "Success Stories" subforum. What have you accomplished that you're bragging about, @bradlington?