engine and drivetrain Valve Cover Breather

[sirius815]

I thought long and hard about running an exhaust venturi system, but am thinking now to just run a line to the intake manifold itself where the smog used to go.  (Including a small PVC valve as well to "limit" the amount of vacuum in the sump).

[lilcphoto]

I'll definitely be paying more attention to this in the future, but with everybody thats running a DCOE setup, what is the goto for the valve cover breather? With the people that have installed one of those nifty catch cans, how often do you find you need to drain them?

 

I am holding off on my DCOE install until I have most of the variables figured out. This is one that I didn't register until I realized I'm going to have to tackle it at some point, and the trumpets don't really have an intake port for the vent (though I might consider making an air cleaner box with separate port for the valve breather). 

 

$40-$50 doesn't seem too bad for a fancy catch can, but it is one extra thing to consider with the DCOE swap.

[jimk]

Maybe not but given that the intake is a plentiful source of vacuum why would other manufacturers put a PCV valve in the exhaust in order to draw a vacuum?

Of course the original BMW breather includes a small source of direct vacuum but this is only small and is supposed to 'assist' the blow by into the carb.

To be fair the blow by produced by the engine is not really 'air' but the oily gas can definitely dilute the intake charge

Mfrs also provide an air intake to the crankcase for when the PCV is pulling more vapors than what the engine is producing and "Ventillates" the crankcase.  Mfrs selet a PCV flow rate that is more than what a new engine has in blow-by volume but as the engine wears, there is more blow-by than what the PCV draws.  So look in the air cleaner of well used engine with a PCV system and the oil in the housing is from when the PCV can't draw all that is produced.  It also happens on WOT when there is little or no manifold vacuum.

There is also water vapor in the vented gases as well, it is a product of combustion and the ring blow-by of those gases.  So if a catch can can be kept hot there wil be very little to dump.  Most of the sludge is water/oil mixture.

[ALW62]

Recently plumbed the breather hose back into the Weber carb (38) base plate prior to this it was an atmospheric discharge style.  Reason for this was due to the amount of noxious vapor I was getting in the cars cabin I thought this might solve this.  This work was done during the early rainy (Seattle) winter so when going for test drives after the work I had all the windows closed tight.  I didn't get any of the odor in the cabin so I thought problem solved....lately as the weather is getting nicer I'll crack a wing window or even roll a window down partial or completely.  When I crack the windows whether partially or full open I am once again getting the noxious vapors back into the car.  Any ideas or remedies you folks can lay on me most appreciated.

['76mintgrün'02]

Engine bay air can get sucked into the cabin, if you do not have all of the seals installed.

 

Do you have the rubber seal across the back of the hood and the two on the sides, that fit over the hood clamping bar?  

The rubber drainage 'tubes' at the bottom of the heater's intake trough are important as well.

Elephant trunks, they are sometimes called.

 

Exhaust can also get sucked in through the trunk, if the seal is not fitting tightly. 

The metal that the seal is on is thin and leaning on it will bend it down and the seal will not make good contact with the trunk lid.  You can slip a dollar bill in and close the lid, while moving it around to check for tightness.  Bend the metal under the seal back up, if needed.

 

I saw sootiness on the underside of my trunk lid, where the seal was not tight.

[ALW62]

The seals make good sense especially as this seems to only occur when the windows are cracked and or rolled down.  Perhaps a vacuum effect of sorts as doesn’t occur when the windows are all closed and the cabin is closed up tight.  Thank you will look into this today ??

[Hodgepodge]

Question.  Earlier on, somebody posted a link to eBay showing several of these oil catch cans.  Most don't seem to have lids or drains.  How the hell do you empty them?  

 

 

[Hodgepodge]

Tony, the seals on the hood and on the sides of the space that houses the wiper motor keep the engine air from the cabin BUT, there are other ways for engine fumes to get into the cabin.    It is important to have good hood seals, but you also want to check for air coming into the cabin from bad grommets, the pedal box, around the A/C hoses if you have them, etc.   If you cabin vent is closed and  1) you think the seals on the cabin vent flappers are OK, and 2) you are still getting smells with an open window, it is probably not just the hood seals.  

 

Try this.   Get some plastic and tape and close off the entire firewall-heater-valve-wiper-motor area under the windshoeld.   Go for a drive to check.  Still getting smell?  Then it is something other than or in addition to the hood seals.  Anywhere you can see light from within the cabin is a potential source of the smell.  Check all the way back to the foam ring on your shifter.  

 

Hope that helps.  

 

Scott

 

 

 

[ALW62]

Thank you, Scott.  I'll give this a go too.

 

Am I on the right track in thinking when the windows are cracked or opened this creates a vacuum or air draw into the cabin because when the windows are closed and cabin is sealed tight the odor is not present.  Lastly would missing or failed seals also be a source of a whistling noise which occurs on HWY at around 60-65 mph?  The whistle noise seems to originate from bottom L side of the windshield, the area in and around this zone.

 

 

[jrhone]

Engine/exhaust smell in the cabin when the windows are open can be the trunk. To test that theory get some of those tree air fresheners. Put two in the trunk. I put them on the shock towers. Go for a drive. Smell like air freshener?  It’s coming from the trunk. I did this and it was soooo strong it was like the air fresheners were in the steering wheel. New trunk seals helped greatly. 

[Hodgepodge]

Positive pressure in the front from the firewall and then it exits in the back 1/4 or so of the open windows.  Different cars have different flow patterns but if you think of how pressure is low on top of an aircraft wing, the same principal applies here.  There may be low pressure to create a vacuum behind the mirrors or in a sun roof if you have one.  

 

The trunk idea is an interesting one.  Never thought of that.  There are a few openings from the trunk into tha cabin for wiring but they are usually filled with foam...but the speaker openings might be letting air in.  Hmm.   

[David Layton]

My tii came with a large K&N filter on the air intake and the valve cover breather is a small K&N breather on a 90 degree piece of hose in the valve cover outlet.  At the elbow of the 90 degree bend, there is a hollow tube pierced in connecting the small air line from the throttle intake to the hose on the valve cover breather.  The valve cover is a tii unit. 

 

This looks a bit haphazard and possibly diminishing the performance.  What is the best venting strategy for the tii?  I do still have the large factory intake cannister, but I would prefer not to use it as t blocks access to the intake side of the motor.

 

 

[Conserv]

No one has come up with a better solution, from a breathing and engine-protection perspective, than the factory tii airbox. Alpina’s version simply removed the front and rear snorkels from the airbox, keeping the dual filters and large center box. Get the engine set up correctly and you shouldn’t need frequent access to the left side of the engine.

 

Regards,

 

Steve

 

Edited August 10, 2018 by Conserv

[71bmr02]

I designed and made a recovery tank for the crankcase fumes where the water laden fumes are routed to near the bottom of the tank and a shorter hose breathes the "cleaner water oil removed" fumes back thru the carb.  I didn't know just how efficient it would be till it was first emptied after running during cold weather.  One thing about running in cold weather is the engine  takes a long time to get up to normal operating temp and during that time a lot of water vapor is generated in the crankcase.  if it isn't routed thru a catch can, it is breathed straight into the engine creating potential for carbon build up on valves and pistons.

On another note, Steve's observation about factory system being good is somewhat correct because it does allow cold air to be drawn into the engine in warm weather and warm air during cold weather.  I quantified that with remote thermometers and the upshot is the air drawn into the motor from the outside(factory system modded for a k&n filter) during a hot summer day is several degrees cooler with a stock system vs the open filter type you currently have installed.

One big pool of hot liquid that definitely needs cooling and possibly more so  than incoming air is the oil.  My next cooling project will be an oil cooler. 

[Whaledriver]

Here is my Moroso catch can install. There is a drain petcock on the bottom for draining the can. Since I installed it, I no longer have oil accumulating in my carb filter.