Catch Can Debate

[Calum]

Originally Posted by King Tut

I think your plan would work, it should give the advantages of both systems all in one. Generally a filter is used to catch that last bit of oil in the air as it leaves the VTA catch can. The majority of the oil should be caught in a properly designed catch can.

Agreed.

[Model Citizen]

My 2 input vta can of nair zip tied to a bookend edition catch can works tits.

[sw20kosh]

Originally Posted by Model Citizen

My 2 input vta can of nair zip tied to a bookend edition catch can works tits.

pic?

[Model Citizen]

http://flic.kr/p/nWa5Ss



http://flic.kr/p/nDNtbi


Not at home

Had these on flickr

Mounting is bookend under the battery zip tied. Worked fine for a season of autox and track days. Had a diy pvc recirc can. Worked great till i deformed it one hot autox.

[yomny]

I've read through most of this thread but can't really answer my question as to why the need for two cans? Ive read that one's for the PCV line and the other for the crank case vent. Is it really necessary for boosted applications. If trying to do this right, whats the best way to go, two cans? i was looking at the radium can but the two can system costs about $400. Thanks for your help.

[kiichiro]

2 brz
100k cumulative miles
15-20 track days
no AOS or catch can
save your money
ran all my oil breathers right to my sc intake, no issues

[Calum]

Originally Posted by yomny

I've read through most of this thread but can't really answer my question as to why the need for two cans? Ive read that one's for the PCV line and the other for the crank case vent. Is it really necessary for boosted applications. If trying to do this right, whats the best way to go, two cans? i was looking at the radium can but the two can system costs about $400. Thanks for your help.

One can would sit between the crankcase and the intake manifold. As you don't want oil in the intake manifold a can here is a must, vented or not. There should be a check valve in this line, if it isn't vented, to prevent pressurizing the crankcase with boost.

The other line goes from crankcase to intake before the throttle plate. The only reason it goes there is allow the vapours exiting the crankcase to be burnt during combustion. These vapours are a lot less harmful burnt then not. As a side benefit the intake filter will also filter the air that will go into this tube when the crankcase is in a slight vacuum. (When the check valve in the other line is open.) You can just put a filter on that tube and not route it to the intake at all. The down side is the harm to the environment and the possible mess if oil comes out of that tube.

If you put a filter or vented can on the second line your crankcase will run vta during wot and/or when under boost. This is similar to the stock setup in that regard. If you put a non vented can there it'll still be vta, the atmosphere is just gonna be that inside the intake, which isn't really significant.

If you run a vented can on either tube, make sure you plug the hole left in the intake.

[Rosticles]

Thank you Calum, I wish you had summed it up like that for me when I started trying to figure out the problem. I am going to use a Mishimoto can on the PCV side and a MightyMouse breather can on the vent side. I am also going to use a check valve arrangement to redirect the PCV to the breather under boost, like in this picture:

[yomny]

So for boosted applications or NA whats better for the car VTA or closed system? Thanks for the detailed explanation, this helps a lot. I was thinking of running the dual Radium setup. If you had to do one only which would you run from crankcase to manifold? Thanks @Calum

[Rosticles]

For NA you only need one can and it should definitely be the PCV to manifold. For boosted applications you should add a check valve to the manifold line. A dual can setup is only needed in a boosted application, and even then maybe not. I would not suggest a pure VTA for NA because it may mess with the tune.

[yomny]

So it'll be good to run the one from the pcv to manifold? Doesn't the pcv valve have a check valve or is an extra one needed? Most of these cans that sell for boosted applications don't mention anything about a check valve, how come?

[Rosticles]

http://www.ft86club.com/forums/showthread.php?t=41592
http://www.ft86club.com/forums/showthread.php?t=79339

Both of these threads mention issues with leaking PCVs during boosted manifold situations.

[yomny]

I'll make sure to get one of these little check valves, seems they're good to have with or without a catch can.

[Calum]

Originally Posted by Rosticles

Thank you Calum, I wish you had summed it up like that for me when I started trying to figure out the problem. I am going to use a Mishimoto can on the PCV side and a MightyMouse breather can on the vent side. I am also going to use a check valve arrangement to redirect the PCV to the breather under boost, like in this picture:

I've had this debate too many times on here so I try to avoid it now. But I'm bored so I'll jump in.

Why use a setup to redirect? If you use the redirect method the crank case will vent through the Mighty Mouse Breather while the intake manifold is in boost. If you don't use the redirect method but use a check valve going into the intake manifold, then the crankcase will still vent through the Mighty Mouse Breather when the intake manifold is in boost. Either way the crankcase will be vented through the Mighty Mouse Breather to atmosphere under boost. The only thing you'd gain is flow, IF the flow from the crank case to the MMB is restricted. Somethings telling me the valves and tubes will be more restrictive than whatever baffling might exist at the outlet of the crankcase. Remember you're dealing with roughly 10 psi of pressure differential max. The restriction through all of those valves might eat up a lot of that pressure differential.

As for the benefits of maintaining a positive crank case ventilation system versus venting the crankcase to atmosphere; The VTA setup has been run by many and most reports say it makes no difference to engine life. The advantages are being absolutely sure that crankcase vapours and oil will not enter your intake manifold. Oil will lower the effective octane of the fuel, and clog intake passages. The disadvantages are doing harm to the environment.

A PCV system uses intake manifold vacuum to actively maintain a vacuum in the crankcase under as many engine operating conditions as possible. PCV's have been implemented on every factory vehicle that I know of for decades. It's original purpose was to prevent contamination of the oil from blowby gasses as simply venting the crankcase didn't do a sufficient job. Removing those gasses allows the oil to last longer before it breaks down, and helps maintain its ph balance. The side benefits of a PCV system are that it puts less harmful shit in the atmosphere and it increases sealing of the rings under light loads. The disadvantages are the possibility of putting oil in the intake manifold or intake ducting.

Using the Mishimoto setup, or any of the many alternatives, can allow the best of both worlds. There is still risk of getting oil in the intake, though. A vent to atmosphere setup avoids that possibility, but loses the other benefits.

I have zero desire to reopen the old arguments. I've tried to be as unbiased as possible here but if my bias does show through it's only this one mans opinion. Do your own research, understand the system, and come to your own opinion as to which setup is best for your application.