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Routing crankcase breathers into exhaust

1941Galant

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A friend of mine gave me this idea a few weeks ago, and the more I think about it the more I want to do it. The idea is to create a vacuum in the crankcase, and it would work sort how a sandblaster shoots sand via the pickup tube. I ran into a few issues when thinking about this though.

First, I wanted to weld some AN fittings into the exhaust, after the wideband O2 sensor, and just hook the AN lines right up to that, however the AN line can only withstand 300 degrees, and I am afraid that the exhaust (by the steering rack) will get hotter than that and damage the AN line. So basically, how would I go about hooking lines that can only handle 300* up to an exhaust system that gets hotter than that? My idea was to weld some 1.5" SS pipe onto the exhaust (about 8" or so) and hook the AN lines up to that, but I'm not sure if that would be sufficient.

The second issue that I ran into was what angle would create the most vacuum? At first I wanted to go in at a 45* angle (going with the exhaust flow), but when I got around to thinking about the sandblaster the pickup is perpendicular to the compressed air, and that seems to work well. So what would be the ideal angle to go in at?

The final issue that I could think of is that the exhaust pressure would exceed the crankcase pressure, and the exhaust would move into the crankcase. I was thinking I could put a check valve between the exhaust and valve cover but that defeats the purpose since the crankcase vapors would have nowhere to go. Is this something I would need to worry about?

Here is a picture of how Magnus did it to their drag evo.

DSC00740.jpg


P.S. I did take note to the line that magnus used, but since my car isn't a dedicated race car that will be shut down after each pass I want something that will last a long time.
 

Flip4G63

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Why question would be WHY do you need this in your street driven Galant?
 

Dialcaliper

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I believe 45 degrees or thereabouts is a typical installation. It has to be very near the end of the exhaust to actually pull any kind of vacuum, about where you see it on the Magnus car. Otherwise, it will almost always be pressurizing, instead of pulling vacuum. The best vacuum is created in the mouth of the exhaust a couple inches from the end as it expands and cools into the air, combined with the venturi pickup. If you have a full exhaust, this means far back, definitely after the cat if you have one, possibly after the muffler. You will spew a lot of nasty crap out your tail pipe, if that's something that matters to you. You might be able to rig it up to pull off the tip of an exhaust cut-out that only opens under throttle, so that you're always guaranteed either ambient or vacuum pressure under throttle. You can also use a copper heatsink or some copper tubing right at the junction just like for a wideband.
 

1941Galant

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Thank you so much for your reply Dialcaliper. Running a line to the back of the car (the muffler will be at the end of the exhaust) seems impractical, so I will look into plumbing the lines into an exhaust cutout in the downpipe.

Chris (boostin91awd), that hose looks like the Starlite Racing Hose by aeroquip, but I'm not sure.
 

cOmpressor

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I figured out an answer to all your problems

 

Ted Andkilde

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The detroit iron guys have been doing this for ages, Moroso makes a kit which has backfire "safety" valves which prevent backpressure from popping valve covers and other weak points.

click

t
 

Dialcaliper

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If you have a dump pipe, you could also route it to the tip of that.

The a double catch-can/check valve setup works just as well if not better, as you will have vacuum at all times (PCV to the manifold off-boost, and though the catch can into the intake when the turbo is sucking vacuum. With a proper catch can or air/oil separator, the blowby will condense in the can, and not pass into the turbo. Honestly, except for lacking catch cans, the stock system is a better design to maintain slight crankcase vacuum under boost and pull fresh air in off boost, where other approaches only really get you one of those two.
 

atc250r

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Backpressure is my "problem" with it. If you run a full exhaust (or any kind of muffler after the vent) then you'll just end up pushing back pressure into the crankcase if the the exhaust pressure is greater than the pressure in the crankcase. Even if that never happens and even with the Moroso check valves, you're going to be working against whatever pressure there is between the exhaust if you put it pre-muffler which is less efficient than letting it vent to atmosphere. At the same time, making the hose long enough to go all the way to the back bumper is counter productive since due to the the length of the hose it will possibly become a restriction in and of itself. Some things that work well on race cars just don't translate well onto the street, this is one of them. I simply threaded 1/8" NPT to 3/8" barbed brass fittings into both my PCV hole and my vent hole in my valve cover and ran two pieces of 3/8" fuel line from them down to the area that my A/C drain was. It saves the mess that you get from an oil catch can's breather and you don't have to drain it. Until PCV valves were used in the 60's, that was how most cars were. My 1996 Dodge diesel is like that.

John
 
Last edited:

Polish

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I agree with John about the Exhaust pressure issue, fwiw...
 

1941Galant

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For now I have abandoned the idea of routing the breathers into the exhaust because of the possibility of the exhaust pressure exceeding the crankcase pressure, or the fact that I would need to run 12ft of line to the back of the car. I like the idea of using an exhaust cutout in the downpipe and plumbing the breathers into that, however the more I think of it I don't really need a cutout since my exhaust is pretty free flowing already. The idea of plumbing the breathers into the dump tube did cross my mind, but I don't really want to do that. I do like the catch can hooked up to the intake manifold and turbo inlet with check valves. I am going to see about having someone make me one. After all of this discussion I may end up modifying the catch can I already have to use the -10 AN lines coming off of my valve cover just due to the fact that I am pretty broke, and I want to get this car running in a relatively short period of time. If I do go that route, I will pick this up as a winter project though.
 

turbowop

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I still don't understand why some people have this fear of just running a catch can? Theories abound about the crankcase needing fresh vacuum air, etc, but running both lines to a breather/catch can works fine and I certainly haven't seen any negatives after running both cars like this, one for many thousand miles. Drain it once or twice between oil changes...good to go. /ubbthreads/images/graemlins/dunno.gif
 

1941Galant

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I'm not afraid of running a normal catch can, I have just been reading about how creating a vacuum in the crankcase can actually increase power. My thought was that if I could pull a little more power out of this thing for relatively cheap (not using a vacuum pump), why not?


Here are some of the articles that I was reading.

click

"Dean Nickerson of Nickerson Performance in Bristol Pennsylvania did a dyno test where he compared several vacuum pumps. He used the GZ Motorsports smaller Sportsman Pump which is actually a modified version of the Saginaw OEM style pump used by GM and Ford. The Sportsman pump was worth a 30hp gain on a 555ci BBC as compared to just breathers in the valve covers. He also reported better results with the GZ Motorsports pump over two other popular vacuum pumps."

I do realize that this is on a big chebby engine, and the guy is using an actual vacuum pump instead of exhaust or intake, but the same idea of creating a vacuum in the crankcase is still there.


click

"Better ring seal, less oil windage, less oil leaking, and less parasitic losses if I am not mistaken."

There are more sites out there that list actual hp gains by creating a vacuum in the crankcase, the majority of those are using a vacuum pump though.
 

atc250r

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I don't think its a "fear" of running the catch can. Mine had a breather and it misted the engine bay around it. Just plumbing the vent(s) down to the ground will eliminate you having to drain a catch can, cost nothing, and will not make a mess underhood.

John
 

turbowop

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You guys should know how anal I am about keeping my car clean by now. /ubbthreads/images/graemlins/tongue.gif That said...if my catch can/breather were misting oil everywhere, I wouldn't be running one. Mine puts off some steam, but that's about it. /ubbthreads/images/graemlins/dunno.gif
 

bazeng

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I've tried using the vac-u-pan stuff a while back.

It didn't work simply due to the backpressure in the exhaust system.
Like said about, it has to be a free flowing exhaust. So it works great on race cars, but any vehicle with a full exhaust / a cat or a muffler will suffer backpressure which means the one way valve will stay closed and you will not be venting anything from the crank case. I was blowing smoke galore with this valve so I scrapped it.

It should work if you ran lines all the way back to the tips of you muffler apart from that, maybe a vac pump?
Or just go back into your intake pipe but you will get oil into your intake / cooler / turbo.

I am currently running a catch can with 2 long hoses running down to the bottom of the car (the vent the gas).

So I'm still catching the liquid / fumes etc, but not allowing the nasty smell to leak into the cabin.

My next attempt will probably be using a pipe which sits under the car, so when moving, the air will be pulling vac out of the pipe and working like the exhaust gas. It'll only work when moving though.
 

Dialcaliper

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This is the right way to do it. You can make your own catch cans if you have fabrication equipment, but you need to make sure they're set up properly, kind of like this Saikoumitchi Can

The important features are the straw on the inlet, the mesh (stainless steel or brass wool will also work, but not plain steel or copper, as they will corrode) and the release holes, which prevent the liquid from frothing up.

The only improvement I would suggest is a bypass check valve on the VC/intake side that lets fresh air pass directly into the VC instead of going through the can.

Quoting chrisb33:
dual catch can set-up.




 

Jazzyjay

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Charleston, SC
To make a catch can go to your local salvage yard get a air condition dryer off any car that is close to the size you want. after look at it you will see what you will have to do this is what you see on most sportman racers. The exhaust way works great also but you will need to run open exhaust or a cutout
 
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