Crank Case Pressure, Catch Cans and Breathers
https://ls1tech.com/forums/showthrea...ight=catch+can
i had a idea like that..... of course everyone shot it down.
i had a idea like that..... of course everyone shot it down.
Mell, if you are beating on your car 24-7 you might need to add oil regardless. When I went to the track, no matter what motor was in my car, I might end up adding 1/2 qt after making 20 passes.
Old skool Mopars had breathers that were like 4 inches high. That way oil would not slosh right out of the breather.
Old skool Mopars had breathers that were like 4 inches high. That way oil would not slosh right out of the breather.
I've been tempted to try number 2, but I don't plan on running an inlet pipe now so I'm just going to vent with a catch can. Theoretically, it should pull a vacuum similar to how a vacuum pump would, just probably not as strong. If you do like number one, it'll force good circulation of air in there, and likely relieve the pressure, but many people have said that having the crankcase under a slight vacuum (like with a pump) will improve ring seal and can often find a couple horsepower. I've heard 20 hp sometimes on a hi-po setup with a pump.
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From: Norn Iron
No 2 would pose more restrictions.
It has only one opening to atmos from which to breathe. A very small one at that if it uses the stock 10mm hose on the valve cover.
No 1 would be better, offering 2 openings to atmos. But whats the point in running the rear 2, to a catch can, when the other simply ahsa filter stuck on it. It doesnt matter what you think will let air in or out, the one on the valve cover, with just the filter will be the easiest path for oil to escape.
If you want an engine to breathe easily, have as many take-offs as you can, from various points.
If you can do both valve covers, and the valley cover, then all good and well. If that takes one catch can, or more than one, so be it.
If you feel one of those holes needs to let air into the engine, it will anyway, via the catch can.
It has only one opening to atmos from which to breathe. A very small one at that if it uses the stock 10mm hose on the valve cover.
No 1 would be better, offering 2 openings to atmos. But whats the point in running the rear 2, to a catch can, when the other simply ahsa filter stuck on it. It doesnt matter what you think will let air in or out, the one on the valve cover, with just the filter will be the easiest path for oil to escape.
If you want an engine to breathe easily, have as many take-offs as you can, from various points.
If you can do both valve covers, and the valley cover, then all good and well. If that takes one catch can, or more than one, so be it.
If you feel one of those holes needs to let air into the engine, it will anyway, via the catch can.
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From: Norn Iron
The only way it will suck air out, is if there is something to suck it with. ie a pump, or similar.
But creating a vacuum is a better solution. Allowing it to breathe as easily as possible is the next best thing.
But creating a vacuum is a better solution. Allowing it to breathe as easily as possible is the next best thing.
I was always under the impression that the blower inlet tube would draw a little bit of suction from the line, afterall the blower'd sucking 1000+cfm through it.
Sorry if I'm coming off as argumentative, just really want to understand all this as thoroughly as possible.
Sorry if I'm coming off as argumentative, just really want to understand all this as thoroughly as possible.
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From: Norn Iron
If you attached it to the blower inlet, then yes, Im sure it would draw air in. Not sure it would create a vacuum though.
But a lot of people dont want to route the cranckase vent, into the intake, for fear of oil contamination, which is why they vent it seperately to atmos.
An emissions friendly setup would route back into the inlet for sure.
But a lot of people dont want to route the cranckase vent, into the intake, for fear of oil contamination, which is why they vent it seperately to atmos.
An emissions friendly setup would route back into the inlet for sure.
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From: Centrifugal City
Agree, fear of oil into intake.
I haven't seen anyone try an exhaust system evacuation setup yet. Not sure how messy that is out the back of the car, but would be kinda cool.
I haven't seen anyone try an exhaust system evacuation setup yet. Not sure how messy that is out the back of the car, but would be kinda cool.
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From: Bakersfield, Ca.
Originally Posted by MelloYellow
Agree, fear of oil into intake.
I haven't seen anyone try an exhaust system evacuation setup yet. Not sure how messy that is out the back of the car, but would be kinda cool.
I haven't seen anyone try an exhaust system evacuation setup yet. Not sure how messy that is out the back of the car, but would be kinda cool.
I am considering putting a check valve between the catch can and the intake.
Would I still have valve cover pressure issues. I think I would under boost, util at least it equalized.
I don't think I would want to recirculate the catch can oil though. JMO.
Good thread.
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From: Centrifugal City
Ya, I've decided against recirculating. Seems more water and vapors evac to the catch can than pure oil. Better to dump it.
Why would an exhaust evac system affect the valves? You tap into the headers. Post-cats I assume.
If you want to risk injecting oil and need some vacuum under boost you tap the air bridge pre-blower.
Why would an exhaust evac system affect the valves? You tap into the headers. Post-cats I assume.
If you want to risk injecting oil and need some vacuum under boost you tap the air bridge pre-blower.
Originally Posted by MelloYellow
Agree, fear of oil into intake.
I haven't seen anyone try an exhaust system evacuation setup yet. Not sure how messy that is out the back of the car, but would be kinda cool.
I haven't seen anyone try an exhaust system evacuation setup yet. Not sure how messy that is out the back of the car, but would be kinda cool.
I posted pics of MY set up and thats what it is! Not too messy at all!
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From: Bakersfield, Ca.
Originally Posted by MelloYellow
Ya, I've decided against recirculating. Seems more water and vapors evac to the catch can than pure oil. Better to dump it.
Why would an exhaust evac system affect the valves? You tap into the headers. Post-cats I assume.
If you want to risk injecting oil and need some vacuum under boost you tap the air bridge pre-blower.
Why would an exhaust evac system affect the valves? You tap into the headers. Post-cats I assume.
If you want to risk injecting oil and need some vacuum under boost you tap the air bridge pre-blower.
I have a rear turbo, I do not believe I have a place on the intake to tap into that is always at vacuum. Thats why I am thinking of using a check valve. But I am still concerned about presure build up. I also want to try and keep it emmissions friendly if possible (it may not be).
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From: Centrifugal City
Originally Posted by Arkangel77
I posted pics of MY set up and thats what it is! Not too messy at all!
Teach me to skim a post I started.
I have a yellow car also.
Do you get any oil on your tail?
>> FWIW I've noticed a major difference in the amount of crank case pressure coming out of certain valve or valley nubs. Front Passenger nub has the most crankcase pressure on my car by far. I get almost nothing out of the rear driver nub. Am not sure about LS6 valley nub.
Last edited by MelloYellow; Apr 9, 2005 at 02:50 AM.
Yellow - I do get some Smoke when I punch into WOT BUT nothing on the car itself? I have a Filter/seperator in the works that I hope will stop the oil from freeley flowing out. I plan to Mount it ontop of the Valve cover itself so that anny colected oil will just drip back into the valve cover. Its gona require some welding of a Bung onto the valve cover itself BUT if it works as I hope it will its gona be sweet. If it does not I will just screw in a nipple and be back where I am right now. Good Luck, Lata, Ark
all this effort to draw a vaccum on the crankcase... remember there is no vaccum when you are wide open.. (unless you hook it to the exhaust) and i'm not entirely sure how that would work out on a turbo car.
i been through all this.. just run breathers and have a draw source from in front of the compressor so that at high intake speeds you will have a slight draw and leave it alone and change your oil like a normal person. no oil in the intake, no draining catch cans, no extra fuss under the hood.. thats my opinion.
i been through all this.. just run breathers and have a draw source from in front of the compressor so that at high intake speeds you will have a slight draw and leave it alone and change your oil like a normal person. no oil in the intake, no draining catch cans, no extra fuss under the hood.. thats my opinion.
Originally Posted by KAOS
in those pics its going from the valve covers to the can then back into what, is that the air filter or and additional air filter?
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From: Norn Iron
Strictly speaking. If your catch can system is working properly, then re-routing back into the intake would be fine.
If its working, NO oil should get through, and only fumes from the crankcase. But as I said....most people dont want any, or the risk of any.
If its working, NO oil should get through, and only fumes from the crankcase. But as I said....most people dont want any, or the risk of any.