Lets Talk About Crankcase Pressure and Catch Cans!
 

Lets talk about some ways to get rid of excess crankcase pressure and ways to set up catch cans etc. Whos currently running a catch can system? How is your PCV system set up? Where do you vent the extra pressure and gases to? Do you use breather filters, a breather on the oil cap, anyone using a Venturi Style setup to the exhaust, check valves... etc etc etc.

My eventual setup will consist of:

PCV valve on valve cover to Catch Can (CC)to Throttle Body (this is how the factory system is set up minus the CC) and then the drivers side valve cover port will be linked up to a catch can and then either be routed to atmosphere with a filter or port to CC to exhaust using the venturi method. The idea of this is to be able to pull an appropriate amount of vaccum from the crankcase to remove any excess gas/oil etc from the crankcase and allow it to be replaced with good clean fresh air while at the same time filtering out any oil or blowby. My car requires a constant vaccum to perform at it's best.

Discuss. I'm particular interested in turbocharged/supercharged applications.

I'm hoping to get some gurus in here that are experienced in these sort of things and may be interested in doing some experimentation for this. I'd happily donate my car and dp to play with the exhaust style venturi method for this. It'll require some welding, some testing using a vaccum gauge to determine how much vaccum this method is pulling... too much and it'll start to pull oil away from where it's most needed. If it turns out to be an appropriate level of vaccum then I'll be hooking it up with a 1 way check valve and a catch can and dumping extra gases out the exhaust. I understand this may not be actually legal, but my stock exhaust isn't legal anyway so w(who)tf cares anymore. this will be on my catless dp setup that i will eventually be adding a cat to.

My friend has a catch can in between valve cover and the vacuum port in the throttle body which is the stock setup in the Yamaha V6 SHO motor. He has installed a Vortech in his motor. I have seen vacuum pumps installed on SBC and SBF used to create a vacuum in the crankcase and vented into the air.

Bob

^^^this is how step 1 of my setup will be

If you have excessive crankcase pressure, in my experience it has always been the result of a leaky intake on a boosted motor. Boost blowing into the crankcase.

Otherwise you have a ring seal problem. Which your motor doesn't have.



I would run a hose from your air intake, to a catch can, and then to the valve cover.

I agree with Enkie. I've seen Supras with wiggin's clamps on the Radiator hoses because they are pressurizing the block. Is the car burning oil? They make oil catch cans that have moisture (oil) separators that can work well for for this. By the way the supra with the wiggins clamp was totaled when that thing let loose and leaked radiator fluid on the rears.

^^^ no issues with my car currently that aren't already figured out (I am burning oil but it's soon to be fixed, figured out the issue a bit ago but haven't had the time to fix it yet... busy week for me.) :) just a topic that i'd like to keep open for discussion. (there is a large and busy thread on my other forum about this and i'd like to hear your theories and ideas on it)

Like I said, I'll be running a catch can between the pcv valve and the throttle body vacuum nipple, and then an additional system between the valve cover and either the intake or the exhaust.

I'm familiar with catching oil and different ways to do it... just want to look mostly at ways to help get rid of the extra gases and oil specifically using the venturi method with the exhaust system mentioned above.

Enkei, can you clarify your leaking intake comment above? I'm not sure I'm quite following you. Are you referring to the intake valves in the head, or the intake manifold, or the intake piping to the turbo... lets be specific :) I'm imagining your referring to the intake valves but I could be wrong.

I may have a problem with my piston rings as well as a matter of fact, I've got low compression right now, and I'm going to need to do another compression test to confirm if solved or not.

Well here are my $0.02.

1) I like the addition of before the TB. It is always best to keep oil and fluids out of the intake track. LS motors have this problem and we use CC with oil separators. THey go for ~$70.

2) Venturi setup: These are use a lot of ship's to draw a vacuum on our main condensers (steam) We run steam through the Venturi and draw a strong vacuum that removes non-condensable gasses from the condenser. I would say if you are going to experiment with this install a differential pressure gage to measure the delta between across the venturi and a pressure gage upstream of the venturi to measure the pressure build up between it and the turbo. The DP cell will indicate the motive force for the venturi. The upstream pressure gage will indicate the cost you are paying for having the venturi in since you will have least potential across the turbine wheel. Finally I would find something prevent it from sucking up oil. Like weld in a baffle close to the suction. Every ejection pump (it's the laymans term for what you want to install) has a strong suction it would be possible (with a good venturi) to suck the oil pan dry VERY quickly. SUrface ships actually use them for dewatering flooded spaces.

NOW we're talking!!!

CC = Ebay, 30 bucks shipped 750ml whoot!!!

Ok onto the important stuff... I happen to know that there are at least 1 or 2 srts and multiple other race cars (race not street cars) that are running a venturi setup to the exhaust. Don't have a way to contact them though.

here you mentioned: can you clarify this for me? are you suggesting a power loss by using this system? I'm really wanting to try this, maybe hook up a vacuum gauge to my DP (have an extra bung I can use actually) and see how much it's pulling. If its in a good range i'd like to give it a shot and see whats up. it'll be valve cover to CC to check Valve to exhaust.

A turbine (exhaust side) is a machine designed to convert the fluid and thermal energy in the exhaust into mechanical energy in the form of the rotating shaft. In order to do this it needs a pressure differential across the turbine wheel. That means you want the turbo to be as close to the exhaust ports with no restrictions (i.e. wrx cat). and have as free flowing exhaust afterwards as possible. This means the pressure and heat before the turbo are as high as possible and the pressure after the tubro as low as possible. This will make the turbo spool up as fast as possible.

A venturi works by reducing the cross section in a pipe band. Mass flow rate is constant and there there is no work in to compress the gas so volumetric flow rate is also constant. This means that the fluid (exhaust gasses) must accelerate through the restriction. The high speed of the fluid will "molecularly entrain" the gasses in the cavity you are trying to draw a vacuum in thus removing the unwanted fluids. The problem is that you can't get anything for free. So you need a differential pressure in order to get the exhaust to accelerate across the venturi. Well you final pressure is atmosphere so it can't go down. That means that the differential pressure is generated by a pressure increase before the venturi. Essentially you are increasing the system head losses.

Now the venturis that I have seen are all medium to small diameter convergent divergent nozzles. They draw almost perfect vacuums of 14.7 psiv. Since you don't need that kind of vacuum then you can run a much larger I.D. on the venturi and not cause as much of a restriction.

How about trying to just tap the pipe and seeing if the exhaust has enough velocity to draw a suction without a venturi. Also if you do this make sure to put the tap behind any restrictions like the turbo or the cat because if the pipe is under pressure then you could end up pumping gasses into the crank case.

^^^ gettin my head around this. Thanks BADDASSC6, I'm on my phone so I'll respond later in full.

Chrysler motors burn oil. My friends Turbo 420A burns oil and my Neon consumes more oil than my Vette motor does. How much oil does your motor consume? Are we talking rotary consumption? Or like only a quart every other month?

I don't like the idea of modifying your exhaust to scavenge crankcase pressure. First of all, I doubt you'll pass smog like that, especially with your luck. Second of all, you don't need it. If you're that concerned with it and you're too poor or lazy to find the real problem, go with a vacuum pump. If you can't suck enough air with the intake.

BADDASS, btw, when my HG/ intake was leaking boost, my heater hose popped off at about 100mph WOT. Sprayed directly on my header. I've never seen that much steam before in my life. And I've been to Yellow Stone.

I have a simpler explanation for a turbine, and it's more fun, but probably less accurate (btw I don't know why you guys are talking about turbines because I didn't read most of this post).

Turbine = Turbocharged rocket engine.

Just like a rocket engine, a turbine ignites fuel mixed with oxidizer in a chamber. It blows out of the chamber through a fan at the back of the turbine, (like an exhaust wheel in a turbo) which spins a shaft which spins the fan in front of the turbine (like a compressor wheel in a turbo) that sucks the air into the rocket chamber. (Technical term, hahaha).

Oh you guys are just talking about turbos, nevermind. Thought you were talking about turbine engines.

I don't understand this but a catch can on an existing line is actually illegal. Just run one inline of your vacuum line and call it a day. Or even cap off the nipple on the t/b and vent it after the catch can.

I run a catch can on my Eclipse and it's just a air filter from Lowes and works great.

You can't use manifold vacuum to vent the crankcase on a boosted motor. You're supposed to move it to the air intake. There is always suction there.

Crank case pressure.
 

I had a variation of this problem, crankcase pressure, I was James Bond putting out as much smoke as the 7th fleet. I'm running a 3.7-TT mounted below the exhaust manifolds. I used a scavenge pump set up with 3/4" return lines and a "T" link between both .86 Turbos, works like a charm. The pump is sold local (RB Racing-Long Beach) for about $275, the fittings and hose parts run about $80.00. The upgrade gives out a slight hum like a fan set up, the RB Racing site is attached with the write up. Good luck.

http://www.rbracing-rsr.com/oilsystems.htm

Right, it has to go to the suction side of the turbo. At least that is what I'm going to do mine when i finally get my turbo in.

One thing I never understood is why does my v6 have a pcv on the front bank and not the rear bank.

Most cars have one vacuum side at the pcv valve, another "breather" line to let clean air in. Both banks are open to the same pressure through the block.

after closer consideration and a little better of an understanding of this system I believe you are right sir. I may just try that inside of an actual venturi system.

Enkei, not worried about passing smog with this setup cause I wont even be able to pass with a catch can. That means anytime I have to smog my car I'll have to put it to stock anyway. Might as well run this setup. Besides, the catless setup is illegal anyway... actually even if I added a cat it'd STILL be illegal thanks to wonderful california. And it only costs 25 to fix. So EFF it.

The idea of this is to prevent ANY fumes or oil blowby to possibly make it into the turbo, thats why Im looking into it this way. All else fails and I opt for the typical setup it'll instead by valve cover to catch can to intake.

Damian,

You're correct and it's absolutely retarded. Any modification to the PCV system (including the wrong kind of hose) is illegal. A line to the exhaust to the untrained eye of a non car car enthusiast will easily mistake the exhaust routed line for a stock setup. If I ever make the mistake of letting someone pop my hood again. :surrender: I'm also using a filter from Home Depot (it's a husky air compressor filter at the moment) but it's volume is too small and its gettin to be a pain in the ass.

Enkei, thats ridiculous because thats the way these cars are set up. Go check your moms. PCV on the passenger side of valve cover is routed directly to the vacuum nipple on the throttle body. thats the main reason for my catch can between those two points. oil condenses and settles in the lower coldside pipe which is the dumbest idea ever.

Kdracer73, ding ding ding!!! My PCV is routed to the intake (throttle body actually), and the "breather" is routed to the intake on the turbo side. blow by will still be expelled through either location.

Makes sense.

Blackboost, did you remove all the guts on that filter? If not, do it. Works much better that way.

^^^gonna do that asap, haven't had time :(

Dude, that is fing retarded. But I have a solution for you, try this before you get crazy with welding ports on your exhaust for suction: cut the blue arrow hose, install a vacuum T; remove the red arrow hose, and install it into the T on the blue arrow hose; cap off the throttle body vacuum port with a rubber cap.

This is such an easy mod I'm going to be mad if you don't at least try it. Those hoses are so close it's begging for it.

this. lol for real.

and thats an interesting idea.. my hoses are not that close together tho, cold air intake kinda moves that one a bit. I'm trying to avoid cutting lines at first if possible lol. If I throw a catch can between those two I may definitely try it, but as long as i'm going to throw a catch can in I might as well leave it hooked up the way it is from the dealer just without the excess oil sitting in my cold piping working it's way up to the throttle body and IM under 16 PSI.

My current setup is:

PCV to CC/Filter thing to intake. throttle body is capped. Once I get my CC I'll be changing it up.

ps. detail that engine bay for her.. lol looks dirty.

I wouldn't worry about the catch can, it will just decrease suction. And who cares if your TB sucks up a little oil, I don't think it will hurt anything.

P.S. Don't worry about cutting vacuum hoses. You can always slide them onto a pastic fitting from Autozone (next to the Ts) to reconnect. No one will give you crap about that.

If you pull the guts out of that filter, it will work wonders. I drive 80 miles round trip from work and I dump mine every other week because it's full.

I've pulled off many intake manifolds that are coated with nasty oil crap all over the inside. I pulled my intake manifold off last week and I've had the catch can installed for 40k now and there was no oil anywhere inside.

Also, gut that PCV. I cut mine in half with a dremel wheel and the guts fell out. If you don't the intake might not make enough suction to open the valve at idle.

Good idea. I'll do that when Im boosted.

Here's why I want a CC: VW engine who opted not to run one.



no effing thank you

Besides, introducing engine oil into the combustion chamber will cause knock. Again, something I dont particularly want to happen.

I will also be gutting my filter, just haven't had a moment. That's going to be today or tomorrow for sure thought. F gutting the PCV though. That sounds like a really dumb idea to me. The factory PCV is basically designed to be a 1 way valve that allows air to leave the crankcase but not allow it to flow the opposite direction. Gutting that would seem to be a bad idea. Albeit the stocker leaks something awful, that leads to me another discussion. 1 way check valves. if on could be found that has sufficient flow, is a big enough size so as not to cause a restriction, and the PCV was gutted/replaced with a -10 fitting or something along those lines... That might be a great alternative. The PCV valve itself is a cheap part that is a factory boost leak. The only way I'll gut it thought is if it's replaced with a check valve. Don't need those gases flowing the wrong way. I'm sure the intake manifold will pull enough pressure to open the valve, thats the way it's designed... my main concern is enough pressure that it forces blowby the wrong way: into the valve cover/head

^^^ I'm glad you caught that, do that on a boosted motor and you have yourself a front and rear main seal to change out. You'd also be introducing combustion byproduct, get enough of that stuff in your system and well you'll see...

That VW motor had far worst issues happening.

No, that's a result of an old engine and worn valve stem seals. My engine is squeaky clean and I don't run one.

Run good gas, synthetic oil, change it regularly and let the engine get hot and open it up, it won't look like that.

I built a breathing system with catch can in the early seventies for the Vette. I just took the catch can out 2 years ago.

I used a 1 gallon paint can (empty:D) for the catch can.

^^^ haha I ran a Coke can in mine for a while with a custom filter my mom gave me out the kitchen sink. ;)

^^^ none of that shit for me hahaha.

http://www.srtforums.com/forums/f180...-cover-533086/

this is a good read, several people are running this style setup. I'm thinking its a good idea.

Skimmed through it, those guys must be pushing some serious power to be worried about the PCV system. Good dedication coming from all of them, seem like a good bunch compared to the ones that I run into around here.

^^^ there are QUITE a few big turbo SRT4s that are pushing some SERIOUS horsepower in a lightass car (2950ish). Not to mention the stock PCV system sucks. The guy who did my tranny swap previously netted 564whp on a 60trim turbo using nothing other than a piggyback. he's working towards 600+ on a fully built motor now. He's just one of MANY. It seems that the number to shoot for with most of our big turbo guys is 500+ whp. I'm settling for not really more than 400whp, that'll get me into my goal ET and also be an excellent road course car with the proper suspension setup. I'm planning on setting the car up to be as reliable as possible with several precautions for the motor safety. IE, pcv, methanol etc. keep those nasty fumes outta my block.