Catch Can Debate

[number1Tango]

Originally Posted by zex

Which radium catch can fits the frs/brz?

its universal i believe

[wootwoot]

Found this on another forum regarding open systems. I have to say... I may be leaning toward this route at this point.

"What I am doing, venting to atmosphere with intake manifold plugged and intake tube plugged to prevent outside air from getting in unmetered.

The breather filters might get some oil vapors because of oil vapors with the blow by gas. But you could get one of those catch cans that are not seald and have a breather on them. This would then have a place for some oil vapors to collect.

Remember the stock pcv line system is designed for emissions reasons while releiving the crank pressure. Since we all mod our cars, run no cats/hfc's, etc... We are breaking the rules anyways. So there is no point in keeping the factory routing. Also catch cans dont work 100% this is the only 100% true bone dry method of ensuring absolute Zero oil in the intake. With the assumptions everything is running properly."

http://forums.evolutionm.net/evo-eng...-breather.html

The downside of course is that it is illegal. I have even heard of a guy almost getting his car impounded due to such a modification. Know your laws and proceed with caution."

[ANTI_LAG]

Originally Posted by wootwoot

Interesting. This is why I started this thread!

Can you help me understand how your system works? I think you plug the intake outlet and the outlet going from the intake manifold so they are air tight and no longer pushing anything into the engine. You then route the hoses from the engine, which are creating vacuum, to your catch can. This means when the engine creates vacuum it sucks clean air through the filter on your catch can. Do I have it correct? Or do I have the vacuum reversed and it is the motor that is pushing the hot gas back into the intake stream? In which case are you plugging the outlets that go into the engine and connecting the PCV to the can so they suck clean air?

If this is correct, I have a few questions and concerns, but I want to make sure I understand what is going on before I ask.

The intake stream via the back of the IM and intake tube get sealed. Then the hoses from the pcv ports on the block run to the catch can, then it simply vents out of the filter up top. Air only goes out, not in. With our system , the pcv system is completely made its own, separate from the intake system of the motor, which is not the case with competitors or the oem which the systems are together. This method has always worked the best on our race and street cars and we only sell what we race.

Look on our initial thread about our system and one of the customers has his own install and review of the product starting on page 2:
http://www.ft86club.com/forums/showt...t=19462&page=2

[ANTI_LAG]

Also running our catch can will not cause any CELs to come on thus allowing full OBD2 Emission compliance.

[wootwoot]

Does oil or oil vapor ever make it out of the filter? I would hate to have oil vapor all over the engine bay.

Also, someone commented on getting an oil smell when driving. How bad is it typically?

Lastly, does the crank pressure swing back and fourth from positive to negative, both pushing out and sucking in air at different times? What about with forced induction?

I am becoming more and more intrigued by your design as I learn more.

[Sportsguy83]

Originally Posted by wootwoot

Lastly, does the crank pressure swing back and fourth from positive to negative, both pushing out and sucking in air at different times? What about with forced induction?

The way I understand it, The PCV valve is a one way valve, air will only come out not in.

[wootwoot]

I am liking this unit. You would need two to do the job. But if you got two and put some mesh/baffling in the necks they would do everything the expensive units do and be 1/3 of the price.

http://www.jegs.com/i/Moroso/710/854...oductId=750108

I REALLY like these units. But again you would need two and that would be expensive. Really nice two chamber design. I wish they made one with two inlets!

http://www.ebay.com/itm/Black-Vented...item3f0abe6936

The research continues....

[Calum]

First lets look at the purpose of the PCV system and how it operates.

The purpose of the positive crankcase ventilation system is to remove blowby gases from the crankcase. This is required to preventing contamination of the oil and preventing crankcase over pressurization. The blowby gases will turn the oil acidic, increase its viscosity and remove it's film strength, which will all cause premature wear. An over pressurization of the crankcase can cause a catastrophic failure of the engine but in order for it to get that bad the oil level would have to be over the height of the dip stick hole. I've seen this happen on a diesel generator when someone tied open the oil supply valve, but it would be very hard to duplicate in a road going engine.

The system is comprised mainly of two hoses in stock form, both start at different ends of the block. The hose closer to the nose of the car goes to the intake duct, up stream of the throttle body. The air at this part of the system is under very mild vacuum. The second hose goes to the plenum of the intake system. Under most driving conditions this area is under much more vacuum then the intake duct.

So, the hose at the front of the engine is the fresh & filtered air supply to the crankcase and the rear hose is removing blowby gasses from the crankcase.

The PCV valve is there to prevent suction from the crankcase to the plenum under wide open throttle so the blowby gases don't mix with the fresh air coming into the engine thus reducing engine power.

Ok, now that's out of the way, what would be the best way to modify this system. If you're leaving the car naturally aspirated and not going crazy with it, remove the tube from the intake duct cap, the duct and put a filter on end of the tube. This will separate the intake system from the PCV system, preventing the very minimal vapors that may escape here from getting into the intake system. If you just leave the tube open you run the risk of having debris enter the crankcase. Next, put some means of separating the oil & contaminates from the air entering the plenum. Something like this is easy to maintain, and works very well. http://www.jegs.com/p/JEGS-Performan...63433/10002/-1

If you're going the route of forced induction or BIG cams that wont make much vacuum, you're gonna want to either change the oil much more often or find some way, other then engine vacuum, to remove the gases. If the car is still mainly street driven the plenum will still be under vacuum most of the time and the system will still operate as it should. For the track only cars, a vacuum pump would be best but they're expensive. (mind you still less then some of the catch cans available.) I've seen plenty of track only cars run a venturi tube off the exhaust but they need the engine to be at wide open throttle or very near to operate, so this wont work on street driven cars.

As for open systems. That's no longer a positive ventilation system. That's a passive system that works mainly on the hope that the blowby gasses will leave the crankcase without contaminating the oil.

[ANTI_LAG]

That's a whole lot of bad information. The hose in the front supply's fresh air to the crankcase?? And if you have forced induction you just change the oil more often??

No the front hose pulls air out of the crankcase all the time, these are dbw vehicles, the throttle body is open at all times, that's how it regulates idle, and no, you can't just change your oil more often on a boosted car, your still going to have no release of air from the crankcase and pressure will build up and next thing you know you'll be blowing dipsticks and seals out, not to mention if the crankcase pressure can't escape you will start pushing oil from the valve stem seals and your car will smoke. And no you can't just throw a filter on the intake tube Pcv inlet nipple.. If you did that you'll have a huge leak after the maf and you will have misfires and the car will run lean. And why would you spend so much time rigging multiple cans to handle both Pcv Ports or trying weird things. Why not just run what's made for the vehicle?

[Calum]

Originally Posted by ANTI_LAG

That's a whole lot of bad information. The hose in the front supply's fresh air to the crankcase?? And if you have forced induction you just change the oil more often??

No the front hose pulls air out of the crankcase all the time, these are dbw vehicles, the throttle body is open at all times, that's how it regulates idle, and no, you can't just change your oil more often on a boosted car, your still going to have no release of air from the crankcase and pressure will build up and next thing you know you'll be blowing dipsticks and seals out, not to mention if the crankcase pressure can't escape you will start pushing oil from the valve stem seals and your car will smoke. And no you can't just throw a filter on the intake tube Pcv inlet nipple.. If you did that you'll have a huge leak after the maf and you will have misfires and the car will run lean. And why would you spend so much time rigging multiple cans to handle both Pcv Ports or trying weird things. Why not just run what's made for the vehicle?

The throttle body may be open, but that doesn't mean it's fully open. At idle and under most driving conditions there's still a large pressure difference across the butterfly of the throttle body. Drive by wire or not, it's still an otto cycle gasoline engine that requires both air and fuel to be regulated in order adjust output power. Otherwise an air leak upstream of the throttle body wouldn't matter.

I wasn't trying to say anyone should seal the block and just change the oil more often. I was trying to say the pressure in the intake plenum, or rather lack of vacuum, will prevent the PCV system from operating correctly. Thus, another means of pulling the blowby gasses from the crankcase will be required.

While I may not have stated it very well, I wasn't trying to say anyone should put a filter on intake duct. I said the intake duct should be capped and the PCV inlet tube going to the front of the block should get the filter. This way no unmetered air will enter the intake system and the crankcase will still get fresh filtered air.

There's nothing weird about what I said, and it would only require one can. What I said was, put a filter (something like this http://www.jegs.com/i/Airaid/028/770-133/10002/-1) on the crankcase inlet, put an air/oil separator in the suction hose, and plug the resultant leak in the intake duct.

[ANTI_LAG]

Originally Posted by Calum

So, the hose at the front of the engine is the fresh & filtered air supply to the crankcase and the rear hose is removing blowby gasses from the crankcase.
Wrong as stated

The PCV valve is there to prevent suction from the crankcase to the plenum under wide open throttle so the blowby gases don't mix with the fresh air coming into the engine thus reducing engine power.
Wrong, the pcv is simply a one way check valve to prevent pressurized air from going into the engine, only air can come out, thats why on a boosted engine there is 0 pressure relief, also on a boosted engine under boost this is the point of most blowby, thus making a bad situation that much worse, this is why closed systems dont do the job on a FI engine.

Ok, now that's out of the way, what would be the best way to modify this system. If you're leaving the car naturally aspirated and not going crazy with it, remove the tube from the intake duct cap the duct and put a filter on end of the tube. This will separate the intake system from the PCV system, preventing the very minimal vapors that may escape here from getting into the intake system. If you just leave the tube open you run the risk of having debris enter the crankcase. Next, put some means of separating the oil & contaminates from the air entering the plenum. Something like this is easy to maintain, and works very well. http://www.jegs.com/p/JEGS-Performan...63433/10002/-1
so put a filter on the front pcv port but still run the rear port to the IM, with a filter inline.... you do know the front and rear ports are connected together through the crankcase.. so basically your still making a huge vacuum leak.
If you're going the route of forced induction or BIG cams that wont make much vacuum, you're gonna want to either change the oil much more often or find some way, other then engine vacuum, to remove the gases. If the car is still mainly street driven the plenum will still be under vacuum most of the time and the system will still operate as it should.

The car will only be under vacuum before boost and idle, so the point of least blowby it will work, other then that your screwed.


A vacuum pump would be best but they're expensive. I've seen plenty of track only cars run a venturi tube off the exhaust but they need the engine to be a wide open throttle or very near to operate so this wont work on street driven cars.
Actually it would pull all the time unless your having reversion issues, but that system, would be completly rediculous to run on these cars.

.

[Calum]

Originally Posted by ANTI_LAG

The car will only be under vacuum before boost and idle, so the point of least blowby it will work, other then that your screwed.

While the engine is in cruise conditions, weather the engine has any kind of forced induction or not, the intake plenum will still be in a vacuum. That's what the throttle body does. It creates the pressure differential required to meter the air going to the combustion chambers. A gasoline engine meters it's power output by adjusting the incoming air and adding fuel to match. If the plenum were pressurized the engine would be making MUCH more power. And while there is some parasitic losses and weight gain from adding a forced induction system, the car still will still require a very similar amount of power to maintain highway speed.

Originally Posted by ANTI_LAG

Actually it would pull all the time.

No, it wont. The venturi will require the exhaust header tube to be full in order to create a vacuum. Given the audience I'll use the example of a carburetor venturi. You can see the venturi tubes in the picture, they're there because if the full width of the throttle opening were used it wouldn't create sufficient vacuum under most driving conditions.

[ANTI_LAG]

If you cruise out of boost which most people on the planet do then I am correct, the rest of what you have said in the above post is a bunch of jibberish and im not going to correct all of it.

And I would like to add im not attacking you as a person but just the bad info you are posting, my reason for this is that bad info gets posted on forums all the time, usually based on opinion rather then fact. When this happens people follow it because they look toward the forums as guidance. In the case of where you posted that you run a filter on the front pcv port but run the back to the IM this might cause damage to the engine for anyone who might follow this advice.

[Calum]

Originally Posted by ANTI_LAG

If you cruise out of boost which most people on the planet do then I am correct, the rest of what you have said in the above post is a bunch of jibberish and im not going to correct all of it.

And I would like to add im not attacking you as a person but just the bad info you are posting, my reason for this is that bad info gets posted on forums all the time, usually based on opinion rather then fact. When this happens people follow it because they look toward the forums as guidance. In the case of where you posted that you run a filter on the front pcv port but run the back to the IM this might cause damage to the engine for anyone who might follow this advice.

I didn't feel attacked, but I appreciate the explanation. The reason for my posts is the same, to correct the misinformation out there.