How to fabricate a proper oil catch can setup.

[surgeon_general]

Venting your crankcase to the atmosphere is not the best thing for your engine. By design the crankcase should be under vacuum at all times. If done properly you will minimize or at best eliminate oil getting through the catch can into your intake tract. In order to do this you will end up needing a welder unless you buy a premade catch can.

I eliminated my pcv valve with the hope of the extra port helping with my problem with blow by. It is not recommended to do so because at idle and low rpms the pcv valve creates crucial vacuum that the line to your intake pipe cannot match. Alot of people get around this by tig welding on some an fittings to the valve cover. Something for you to keep in mind I guess.

So first off pick a good spot for your catch can and start to fabricate your catch can. I picked a spot underneath the wiper motor that was out of the way. Plan out your catch can. You need to designate ports for inlets and outlets. You need to pick a spot for a drain as well. Once you have this setup make sure you think about baffles to help stop the oil. If you create different pockets, make sure you have a spot for any oil to drain out of it.

Once you have it all planned out, go ahead and weld the catch can shut. Take your time welding. Remember every pin hole you leave will have to be welded or brazed shut.

After Its all welded shut. Go ahead and pressure test the can. You will be suprised. I went ahead and brazed the leaks.

Now you are on your way. Paint up your catch can and marvel at your job well done. Run your lines. Make sure you use lines that are made for oil and can take under hood temperatures. As you can see My catch can blends in well with the engine bay. And it does not take up much space at all. Yet, it is very adequate in size and able to stop any oil residue from getting into your intake.

 

[99gst_racer]

This thread has been temporarily moved to the Bolt-on Tech section for discussion.




There is one major problem I see with this set-up. Not both of those ports on the valve cover are exits. As air moved out of the PCV valve port, that exiting air must be replaced with something. That's why the other port (side port) is set-up to be an entrance for fresh air. The way it's set-up now, it's not going to circulate in new air for old air - it's just going to circulate the same old vapor that you're trying to rid of.

 

[topstreet]

I kinda like the way it is set up. I dont mean to be oppositional by any means. The only things that I would say are:

-Get rid of the PCV fitting and change it over for a straight through one.

-Also, I have never personally liked dumping oil fumes back into the intake. The idea is that it is better for the environment to burn them then to vent them.

But!... Having vacuum in the crankcase is a really good thing. So many setups have an atmospheric pressure at best. Some times even positive pressure. This is going to hurt ring sealing which will hurt everything else. (oil usage, HP, fuel mileage).

I few small revisions and your in business.

Jake Hanhardt

 

[99gst_racer]

Jake - How much vacuum is ideal? Also, have you ever messed around with using the exhaust system for a source of vacuum?

I agree about the PCV valve. It would be better to either hollow it out or replace it with a standard 1/8" NPT barb fitting.

 

[topstreet]

Jake - How much vacuum is ideal? Also, have you ever messed around with using the exhaust system for a source of vacuum?

Paul, I have not yet set mine up the way I would like to. The new build that I am doing is going to be running the vacuum fittings in the exhaust like you mentioned. This seems ideal to me. It is creating a vacuum that is directly related to exhaust flow, as apposed to engine rpm like a vacuum pump. The intake style does this as well but it would be without the oil in the intake track.

I know the guys that run the big blocks with the vacuum pumps (for example) will hook up vacuum gauges to the block, moniter vacuum and change pulley sized on the dyno to see what works best. They get much more technical about it then I ever will, but it should work much better in theory then just running the catch can that vents to the atmosphere.

Jake Hanhardt

 

[romeen]

Other than keeping oily residue out of the intake manifold I personally don't feel that this will be superior to the stock setup for a daily driver. As I understand it the majority of blow by happens during high speed deceleration when axial ring flutter is at it's maximum. During this state vacuum will approach (in a healthy 4G63) about 24-25 inHg which should provide very good blow by evacuation via the PCV valve. This setup will eliminate this evacuation precisely when it is needed the most instead relying only on the lower relative pressure of the intake pipe for evacuation which is not at it's optimum during this time since you are not under boost and air velocity in not that high. If I am misunderstanding the dynamics here someone correct me.

Also, I doubt a catch can will draw out 100% of the crap in the blow by. Since ALL of the blow by is now being directed to the intake pipe I wonder how much oily residue will ultimately make it past the catch can and into the intake.

IMO, a stock configuration with a seperate catch can for both intake pipe and PCV sides (with the addition of the check valve on PCV side as discussed in other threads) is still the best method.

 

[DSMunknown]

Paul, thanks a huge bunch for moving this for me.

Soon as I saw this "guide" I wanted to ask the OP where the filter was. So....

 

[Rob10_99]

You dont need to get rid of the vapor, its the pressure that needs to be relieved.
Bigger ports and more of them are the only solution when your running high hp with a good amount of blowby.

 

[romeen]

You dont need to get rid of the vapor, its the pressure that needs to be relieved.

Oh c'mon Rob. Too much dry air down there. Get your butt back up here so you can "rust" a bit and you can do some welding for me while you're at it.

Seriously though, I disagree. Both are very important and I think it can be easily argued that blow by vapor evacuation is the more important one. Excessive crankcase pressure will typically blow out the dipstick or may cause leaking around the oil cap. In more severe cases it can blow out more vital seals but I don't think that this is common.

The blow by vapors contain some nasty stuff including corrosive acids and water vapor. If not removed they will mix with the oil and break it down. This breakdown and loss of lubricity will lead to accelerated cylinder wall scoring/wear which in turn allows more blow by and it turns into a vicious cycle.

Of course the two do tend to go hand in hand.

 

[AndrewD5418]

Other than keeping oily residue out of the intake manifold I personally don't feel that this will be superior to the stock setup for a daily driver. As I understand it the majority of blow by happens during high speed deceleration when axial ring flutter is at it's maximum. During this state vacuum will approach (in a healthy 4G63) about 24-25 inHg which should provide very good blow by evacuation via the PCV valve. This setup will eliminate this evacuation precisely when it is needed the most instead relying only on the lower relative pressure of the intake pipe for evacuation which is not at it's optimum during this time since you are not under boost and air velocity in not that high. If I am misunderstanding the dynamics here someone correct me.

Also, I doubt a catch can will draw out 100% of the crap in the blow by. Since ALL of the blow by is now being directed to the intake pipe I wonder how much oily residue will ultimately make it past the catch can and into the intake.

IMO, a stock configuration with a seperate catch can for both intake pipe and PCV sides (with the addition of the check valve on PCV side as discussed in other threads) is still the best method.

Didn't somebody make a vacuum diagram for the separate cans and check valve?

 

[Rob10_99]

Why dont I just run a CO2 injection system into the crankcase! It will extend the life of my oil for 20,000 miles!
Cooling the oil and pushing out bad man gasses!

oh and I hate oregun. Well I might come back for a week or two, I donno...

 

[topstreet]

These more recent comments are not needed in a technical discussion.

Knock it off!

 

[Defiant]

I'm curious just how much blowby people are getting to need all these exotic catch cans. The $3 fuel filter in the breather tube really should be plenty. The car shouldn't put out that ham can's worth of oil in its lifetime.

 

[slowgsr]

I ran a catchcan setup on my dsm, similar to the one above, i see almost no oil in it ever.

My honda would fill the catchcan after a few passes, about 1 Litre. Im guessing the PCV on a honda vs a dsm is much different, as for my honda it was vented from the back of the block.