crankcase vent system with no can

dsmcurse · Oct 7, 2012

hey guys just wanted to get opinions on my crank case ventalation system and share what ive figured out. well, after constantly forgetting to drain my oil catch can i gave up on it and just run my vent hoses to the bottom of my engine bay and have K&N breather filters on the end of each hose.

im just ventin the crap to the atmosphere, but im doin it down low in the engine bay where any oil residue crap would just fling off to the undercaridge of the car and not in the engine bay. i had a nice catch can and experimented with hooking it up to the air filter pipe and what not. i never really like havin the air filter pipe tied into the crankcase pressure system because my turbo was pullin in dirty oil residue air.

i always see the "dipstick spring" mod to hold the dipstick in. it obvious that theres alot of block pressure under high boost. this is why are dipsticks pop out two or three inches after a 30psi power pull. well i figured that dipstick tube would be a great place to vent off some pressure.

i took two dipstick tubes, cut them so they would form a "Y" when welded back together. i cut them in a way that when the stick is in the tube the rubber groment of the top wouldnt poke down inside far enough to block my freeflowin Y shape. i then just hose clamped on a peice of hose that could survive the hottness of being next to the turbo header.

i used to run the block pressure releif off the dipstick tube into the catch can with the two valve cover vents. but like i said the can in my opinion is more trouble than its worth. at the bottom of the dipstick breather hose is a K&N breather filter. the two vents off the top of the valve cover are 5/8" and the dipstick tube thats "y'd" has a 5/8" hose also. this system seems to work the best for me out of all the other combinations ive tried in the past. and my dipstick never ever pops out either and it requires no spring

Kapok6 · Oct 7, 2012

Why not run it to your exhaust/downpipe like the V8 guys? At least that way you get some vacuum in your crankcase? Seen a supra guy that has done it too. Claims 50hp gain.

dsmcurse · Oct 7, 2012

to feed the exhaust the wasted crankcase dirty air it requires a special lil valve thing. the jetboat guys around here where i live use this system on they're race boats that have over transum headers and 5-600 horse all motor V8's. as far as a claimed 50HP gain, i detect a hint of sarcasim from ya...

Kapok6 · Oct 7, 2012

dsmcurse said:
to feed the exhaust the wasted crankcase dirty air it requires a special lil valve thing. the jetboat guys around here where i live use this system on they're race boats that have over transum headers and 5-600 horse all motor V8's. as far as a claimed 50HP gain, i detect a hint of sarcasim from ya...

Anyone running their valve cover breathers into their downpipe?

Still searching for the 50whp reference.

dsmcurse · Oct 7, 2012

ive considered plumbing it into the down pipe. the info from those supra forums sorta makes me wanna try this set-up. thanks for posting the link

Boostdriven · Oct 7, 2012

Kapok6 said:
Why not run it to your exhaust/downpipe like the V8 guys? At least that way you get some vacuum in your crankcase? Seen a supra guy that has done it too. Claims 50hp gain.

Another thing could probably be done is to run your breather hose in to your wastegate dump tube that way there is no back pressure under normal driving conditions because the wastegate is close but when in boost and wastegate opens it woukd create that suction that your talking about.

dsmcurse · Oct 7, 2012

DUDE! thats damn good idea!

Kapok6 · Oct 7, 2012

the check valve in the system linked above prevents back pressure as well. The thing I don't like about the dump tube idea is what about if your running high boost and not full throttle...there is no exhaust traveling through the dump tube to create vacuum.

Just a thought.

habitatguy187 · Oct 7, 2012

If your ventilation is decent enough (which I'm sure yours is now that you have two valve cover bungs and that dipstick mod) you can plumb back into the intake without fear of getting oil in there....and if you're really worried about the oil, go to autozone and buy a $2 inline fuel filter for a lawn mower and put it in there to catch whatever oil may come through.

dsmcurse · Oct 7, 2012

i hate the idea of all that crap settling in a catch can. theres so much gross condinsation/oily/watery/crap sludge that sits in the oil catch can. i would always forget to drain the damn thing any how. so having the vents just have individual lil filters and just hangin the hoses in the bottom of the engine bay seemed like the next best solution. but if i can effectivley rig my crankcase pressure system to breathe into my exhaust would be awsome. all that condisation/oil blow by/ crap stuff would be totally dispossed of and burnt by the hot exhuast. id like to further investigate this idea. im liking it

Boostdriven · Oct 7, 2012

Kapok6 said:
the check valve in the system linked above prevents back pressure as well. The thing I don't like about the dump tube idea is what about if your running high boost and not full throttle...there is no exhaust traveling through the dump tube to create vacuum.

Just a thought.

True but at lease in this case the breather tube would functions just as if it was vented in to open air but with a check valve in place if there is back pressure in the exhaust the check valve is closed and that breather tube becomes useless.

dsmcurse · Oct 7, 2012

very true

Calan · Oct 25, 2012

Just saw this thread, but there usually isn't enough draw in our exhaust system to help with CC ventilation a whole lot, at least not compared to the turbo inlet. It could also possibly skew your wideband output and shorten the sensor's life, depending where you route it.

I would never use a fuel filter inline with a crankcase vent line. Those things are designed to remove particles from a stream of liquid at high pressure; not to remove oil vapor from air at very low pressures. They tend to saturate and create a restriction to airflow in no time, and cause even more CC pressure problems.

gixrman · Oct 25, 2012

You really only need CC evacuation at full throttle. You are moving a lot of air at this point and a crankcase vent after the o2 sensor should cause no problems.

dsmcurse · Oct 28, 2012

Calan, what are your opinions on venting block pressure out of a custom dipstick tube like this? From what I gather you are the catch can master, I'd really like to hear your input on this block pressure releif through the dipstick tube. Thanks

EMX5636 · Oct 28, 2012

The dipstick idea works. I have been reading a few threads on this lately, as I'm building my own setup currently, but I've seen a few people go as far as adding ports into the front balance shaft "bump" in the block below the waterpipe on the trans side. A couple have removed the balance shaft check bolt and replaced it with a fitting running to a catch can for better block pressure removal.

Pressures start in the block, so why not remove at least some of them before they have to travel into the head. I think Calan did this in his blog correct?

Calan · Oct 29, 2012

dsmcurse said:
Calan, what are your opinions on venting block pressure out of a custom dipstick tube like this? From what I gather you are the catch can master, I'd really like to hear your input on this block pressure releif through the dipstick tube. Thanks

@ "catch can master".

The problem I see with venting CC pressure at the dipstick is that you don't always have a clear air path. Depending on what's going on with the oil splashing around in the pan, the oil can block the escape of air up through the dipstick tube. If this wasn't true, you'd just have air flowing out of the dipstick tube when the dipstick pops due to excessive pressure...instead of an oil geyser which is usually what happens.

But, if there isn't a lot of oil in the tube, every little bit helps. There are two main areas that CC pressure causes problems; oil draining from the turbo, and oil draining from the head back into the pan. Removing the pressure at the VC will probably work for most street cars and helps with the turbo draining, but it doesn't solve the potential problem of oil getting from the head back into the pan. This is a real problem on road course cars, where oil starvation can be an issue. So, any place that you can tap below the oil drain passages in the head would be an improvement...as long as you aren't flowing oil out of the port and defeating the purpose of allowing the air to escape.

dsmcurse · Oct 29, 2012

ok so I read that twice and can picture what your sayin. Oil bein directly in path of the "pressure releif" dipstick when pressure pushes at it. When my dipstick used to pop out it would indeed almost always show some signs of oil come out. Since this dipstick mod I can honestly say my dip stick has nevet popped back out since. Even after 35psi power pulls

If you notice in the pictures I posted in the top of this thread u can see my old mount location for my catch can behind the pass side headlight. When I had the can there I ran the two 5/8 hoses off the valve cover into the can and also had that Y shaped dipstick mod hose extend hidden under the radiator support and go all the way into that catch can too.

I once hooked a 1/2"hose from the catchcan and into the air filter pipe. My turbo was always pullin what seemed to be dirty air that way. And like a early mentioned I would always forget to drain my can.

Now I just run hoses down to bottom of bay and put breather filters on bottom of each hose. The dipstick block pressure hose is still long as it transfers from the stick, all the way across bay and down by splash gaurd near tranny.

Here's what's kinda crazy I guess, the two breather filters from the valve cover are the most dirty and show more signs of $hit drippin out than the one block pressurw hose. Is this do to the fact that, that one block hose is twice as long as the two valvecover hoses? Have you ever expeimented with the block pressure releif method? I personally like it cause my stick don't pop out no more and it required no spring. Any thoughts on venting like this and not using the can?

Calan · Oct 29, 2012

dsmcurse said:
I once hooked a 1/2"hose from the catchcan and into the air filter pipe. My turbo was always pullin what seemed to be dirty air that way.

Yep. It takes a special filter material to be able to remove most of the suspended oil and other crap without causing much of a restriction to flow.

I run a clear 1/2" ID hose on mine, just so I can monitor it and verify my catch can is working as designed under different conditions.

dsmcurse said:
Here's what's kinda crazy I guess, the two breather filters from the valve cover are the most dirty and show more signs of $hit drippin out than the one block pressurw hose. Is this do to the fact that, that one block hose is twice as long as the two valvecover hoses?

It's due to the cross-sectional area of the lines; not the length. Hot CC gases rise to the top of the engine. If the largest cross-sectional area of escape is at the VC, less air will be tapped off through a smaller vent line mounted lower, unless there is some type of suction on it. You'll get some flow out of the lower line, but it depends a lot on how large it's diameter is compared to the lines mounted in the VC, and how easily air can get to the top of the motor.

EDIT: The length and any bends in the line do add some restriction to flow, but it's mostly determined by the cross-sectional area of the lines. Larger diameter = better airflow.

I've never personally played around with venting the block directly on a DSM. With a proper catch can/vent/baffle setup, I've never needed to. But, I don't road race my car or push it to those extremes either. If I did, I might be experimenting a bit with that if I started experiencing oil return or excessive pressure issues.

dsmcurse said:
Any thoughts on venting like this and not using the can?

In addition to not being the most popular guy at the environmentalist's parties, you won't meet race regulations at any sanctioned track.

dsmcurse · Oct 29, 2012

Yeah true. The end of that made me laugh. Thanks for the reply man.

Rst303 · Oct 29, 2012

Get 2 weld on check valves and run them to your down pipe might smoke every often once in a while but thats better then checking your breather box every little bit.

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