crankcase ventilation

[digger]

The blowby and vapors go up thought the bitch tube (and likely oil return holes aswell) into the valve cover, then through the baffling system back into the intake due to vacuum. Since they get routed back pre throttle im guessing there is minimal actual vacuum, just whatever is created from the crappy upstream components.
is it significant though compared to venting to atmosphere? as even a little vacuum can move things pretty quickly i guess.

i'm going to a crappy catchcan and then venting to atmosphere with a small filter. Since i'm going to tidy things up i'm thinking of routing back into the airbox via a nice oil/air separator catchcan to avoid oil getting all over the place, or should i say getting more oil all over the place.... i think my hoses are a little small at 3/8" ID in some parts given the stock ones are 14mmID

i'm trying to avoid the remote possibly that the crankcase gets pressurized even slighty.....

what are people doing with their valve cover vent pipes? stock or something else, what size hoses are being used?

silicone is not good for fuel and oil but is it ok for crankcase vent stuff?

[digger]

bump?

[ak-]

Turbo here.

Had two -10 AN fittings welded onto my M20 VC going to a can, with one -10AN line exiting to the turbo's intake elbow for vacuum.
Excellent vacuum, but shitty octane pollution.. oil vapors weren't doing me any favors entering the system again.

Took off the exiting line that went to the intake elbow to vent the catch can to atmosphere, and my octane improved drastically. Had to remove a lot of fuel from my tables and/or was able to add more boost without detonation.

Still wasn't happy with oil burning on deceleration after hard pulls, so I removed the lines that went from the dual ports on the VC to the catch can and now I have even less crank case pressure because it's smoking less on decel.


Conclusion - motor is happier with the two breathers on my VC venting to atmosphere, so I intend to add another breather to my catch can so that I can at least trap oil in my can with sufficient venting from the can (remember I only had 1 exiting line from the can).

The other best known solution that I know is working on an m20 is a vacuum pump that is hooked by a pulley and belt on the driver's side.

Here's some crappy photo's of it:

[digger]

that's in place of power steering? i've thought about a vacuum pump but seems like a big undertaking without sacrificing either power steering or a/c.

the more i think about it the more i think my lines are too small. i've seen people measure blowby on the dyno and you can get 3-5cfm blowby on a m20 sized engine and thats not considered abnormally high. with an 8-10mm hose in my ghetto system the velocity is 50 m/s. i would think that it would be causing some back pressure. im going to upgrade to 16mm

[ak-]

I believe it's in place of and am also on the same page as you, considering I want it as well, but it seems like a big venture.

Measuring 50 m/s when you say m20 sized engines are measuring 3 - 5 CFM is a huge difference :shock: from a 1 to 2inch hose. That's like mad pressure if your numbers are right.
Are you sure?!

[digger]

I believe it's in place of and am also on the same page as you, considering I want it as well, but it seems like a big venture.

Measuring 50 m/s when you say m20 sized engines are measuring 3 - 5 CFM is a huge difference :shock: from a 1 to 2inch hose. That's like mad pressure if your numbers are right.
Are you sure?!

i calculated the 50 m/s. 3-5 cfm through a that size hole means that is what the velocity would be in theory. i have no idea what my blowby cfm is though.

i pulled apart my existing hoses and replaced small diameter sections with something larger. i actually had a 1/4" ID hose joiner in there for some stupid reason, now the limiting size is the catch can itself

[digger]

now that i've made the hoses 16 mm all the way the engine feels happier at the topend best i can describe it revs out a bit cleaner....

[digger]

cleaned out the manifold a couple weeks ago with carby cleaner as there was oil in, did a top end clean with Subaru upper engine cleaner, oil change, spark plug change etc. the manifold after a couple weeks was still perfectly clean

[zaq123]

cleaned out the manifold a couple weeks ago with carby cleaner as there was oil in, did a top end clean with Subaru upper engine cleaner, oil change, spark plug change etc. the manifold after a couple weeks was still perfectly clean

Do you run this setup with ITB? Got any pictures? I'm looking for proper crankcase vent setup once I go ITB.

[ForcedFirebird]

Since they get routed back pre throttle im guessing there is minimal actual vacuum, just whatever is created from the crappy upstream components.

It also has a venturi effect.

[digger]

Do you run this setup with ITB? Got any pictures? I'm looking for proper crankcase vent setup once I go ITB.

I don't but there are plenty of pics I've seen around. It's just a hose connected to a canister with a filter on the end