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Old 02-13-2011, 01:43 PM   #1
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Default Can I (should I) run breather can oil back to the engine?

Apologies if this has been covered, I think I've seen most of the catch-can threads here but I don't recall this being discussed. I'd have a diagram handy of what I'm thinking of but it would be MS paint and done on a laptop touchpad, so I'll spare you. Instead, I'll describe what I'm thinking of doing.

My valvecover (the spare I just picked up, for downtime's sake), with barb fittings toward the front of it, and on the top of the cover as opposed to offset like stock. Both stock holes filled.

The lines run to the car's right, off the VC and along the fuel rail, just above it. The breather is mounted to the firewall to the right of the IM, and drains down into what would be the factory turbo oil drain on the B6.


Is this a good idea, or have I been smoking the drugs?
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Old 02-13-2011, 06:19 PM   #2
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Sure you can drain caught oil back to the sump. This cuts consumption and there is no harm. It's also how the manufacturers do it, mostly the Germans.
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Old 02-18-2011, 01:52 PM   #3
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Any drain back that sees atmospheric pressure on the other end needs to return to the sump below the oil level, very bottom of the pan Or pressure pulses in the crank case gasses will blow the oil back up the drain. been there done that.

The original B6T had provisions in the block and the pan for a crankcase vent in the side of the block and a drain back at the very bottom of the pan. See attached picture the two capped off ports roughly 5/8". Those ports have nothing to do with the turbo the drain back for the turbo is on the other side of the oil pan, the upper one is a crank case vent and the lower one is a drain back. Using the upper one as a drain back made a mess when I tried it.

I have recently added these ports for my setup and rather than venting to atmosphere I will be pulling a slight vaccum with a slash tube in the exhaust.

Bob
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Old 02-18-2011, 02:21 PM   #4
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you've seen the crap that accumulates in the catch can, right? The stuff that you're planning on draining back into your oil system?
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Old 02-18-2011, 02:42 PM   #5
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I've seen what accumulates in your catch can...lol.

bbundy - Interesting.

Actually, to be on the safe side maybe I shouldn't drain back into the engine... My intent was to have a maintenance-free system but that may have been misguided.

What about pretty much the same thing, but no drainback, and tucked away in the fender?
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Old 02-18-2011, 02:46 PM   #6
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Quote:
Originally Posted by sjmarcy View Post
Sure you can drain caught oil back to the sump. This cuts consumption and there is no harm. It's also how the manufacturers do it, mostly the Germans.
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you've seen the crap that accumulates in the catch can, right? The stuff that you're planning on draining back into your oil system?
Ive seen whats in peoples catch cans before, its nasty, but is it harmful or not? With an engine with no catch can, that crud is still in there...
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Old 02-18-2011, 02:52 PM   #7
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The **** that accumulates in MY catch can, as previously seen by koto

FWIW, it was about 30% water, 30% gasoline, and about 30% some other crap I can only describe as some sort of oil/water mixup. Not sure I would want to put the water back into my oil after it has escaped as vapor (though theoretically, it should become vapor again at about 212 degrees ) and not sure I want the gasoline back in there thinning my oil out.
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Old 02-18-2011, 02:57 PM   #8
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Yeah, drainback doesnt sound like the best idea, I was just trying to get a strait answer. With water being in the system like that I think I will stick with venting crank and vc. Bob, how effectively does the slashcut work at drawing vaccum at higher rpms?
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Old 02-18-2011, 03:31 PM   #9
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Originally Posted by fooger03 View Post
The **** that accumulates in MY catch can, as previously seen by koto

FWIW, it was about 30% water, 30% gasoline, and about 30% some other crap I can only describe as some sort of oil/water mixup. Not sure I would want to put the water back into my oil after it has escaped as vapor (though theoretically, it should become vapor again at about 212 degrees ) and not sure I want the gasoline back in there thinning my oil out.
With a slash cut in the exhaust Iím hoping the water and gasoline portions being more volatile than the oil get sucked out the tailpipe. Canít stink any worse than venting them in my engine bay and I donít want them in my intake tract either.

Bob
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Old 02-18-2011, 03:40 PM   #10
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I'm not sure how the water is there in the first place. But that's another debate. I personally wouldn't worry about draining things back in. I'd do it exactly as bbundy is. Pull a vacuum on it (as it is designed, not just an atmosphere vent) to help pull that out, and let it drain back in.

I've got an Escort GT engine in my car which has the dipstick tube at the front near the crank which will probably be where I drain mine back in eventually.
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Old 02-18-2011, 05:26 PM   #11
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I'm copying Bob and setting up a slash cut system too.

For regular under 15psi boost purposes though, I think a VTA catch can with a manual drain will do the job fine.
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Old 02-22-2011, 11:30 AM   #12
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Is the **** in the can mainly down to VTA pulling in air and the moisture within it, which then condensates and mixes with the oil vapour?

So in theory a can without a fresh air feed/vent wont collect the cappuccino

Could be completely wrong mind
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Old 02-22-2011, 01:42 PM   #13
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Is the **** in the can mainly down to VTA pulling in air and the moisture within it, which then condensates and mixes with the oil vapour?

So in theory a can without a fresh air feed/vent wont collect the cappuccino

Could be completely wrong mind
It's the byproducts of combustion that condensates when cold. Think about how much water comes out your tailpipe on cold starts. Its the same thing.

Bob
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Old 02-22-2011, 01:46 PM   #14
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Quote:
Originally Posted by PGD View Post
Is the **** in the can mainly down to VTA pulling in air and the moisture within it, which then condensates and mixes with the oil vapour?

So in theory a can without a fresh air feed/vent wont collect the cappuccino

Could be completely wrong mind
That was always my theory as well.
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Old 02-22-2011, 02:23 PM   #15
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Quote:
Originally Posted by bbundy View Post
I have recently added these ports for my setup and rather than venting to atmosphere I will be pulling a slight vaccum with a slash tube in the exhaust.

Bob
Let me know how that works Ive been thinking about doing this or making a vacuum pump system.
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Old 02-22-2011, 03:03 PM   #16
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Quote:
Originally Posted by bbundy View Post
It's the byproducts of combustion that condensates when cold. Think about how much water comes out your tailpipe on cold starts. Its the same thing.

Bob
Yes…the captured oil is in an accelerated aging environment. Trapped oil returned to the engine is just fine. The OEMs have been quietly doing so for many decades on high performance long oil change interval vehicles. Normally aspirated, supercharged, turbo...
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