(Turbo) Crankcase Ventilation is Important (i.e. my experience with an Amazon catch can)

garrittpwl

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Thought I'd share a discovery that I've had recently for those that don't really think about it or just don't know. Its obvious now that I've learned it but no one comes out directly and says "hey, make sure of this because of this" so lets get to it.

Why is a a catch can important specifically when using running a turbo?

If you're unfamiliar with turbo setups, they require oil (well most, some new fancy ones dont). That oil has to be pumped into the turbo via a feed line, then regulated to a pressure that the turbo can handle and then evacuated via a drain line to the oil pan.

Turbos lower than the oil pan require a scavenger pump to pull the oil from the turbo to the oil pan. Turbos higher than the oil pan can gravity feed back to the pan provided its a steep, smooth straight line.

Now lets get to the point. Since I slapped an on3 kit on my car last summer, I've always had a little smoke at the stop lights here and there. Nothing that a few blips of the throttle couldnt clean up. I equated this to a cheap chinese turbo seal. What I discovered was that in actuality my turbo was not draining efficiently. But wait?! I did everything correct, ran a nice -10 AN line from the turbo with a smooth turn right into the top of the oil pan right?

WRONG!!!! I used an amazon catch can with a vent that was only 3/8 in diameter! So my vent system from the crank case had TWO -8AN lines running to the can and then a single 3/8 vent to atmosphere.

I found that since the crank had such a small vent. I was creating a positive pressure inside the engine, very small but still positive. That pressure would slow the oil in the turbo's drain just enough that it would enventually (long cruises for example) not allow the turbo to drain properly and oil would seep around the seal on the exhaust turbine side. This in turn caused it to smoke!

I watched a video about diesel guys having the same issue, though now it seems common sense. Basically like trying to empty or fill a gas can that doesnt vent properly.

Seems silly but I thought I'd put some info out there in case someone in the future was trying to diag their turbo smoking.

Below I attached a picture of my newly acquired motion raceworks catch can vs the amazon one I was attempting to use. Now I know why they're 200 bucks instead of 30.....

1000002373.jpg
 

tvsn95

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Let me pass on my experience. I have built several turbo/supercharged, including On3.
First a -10 drain is TOO small, you can get a full 5/8" ID drain on the turbo that will then take a 3/4ID hose, I like an extended tube to get away from the high turbine heat. ( no fires), I have made my own. this stops the smoking and leaking problems.
I build my catch cans from PVC, this works well to figure out what you need . then you can build it from better materials.
I also use a GM air injection pump, used in 1990s cars to suck from the original PCV location and blow to the catch can. this is activated with a watts switch to come on at the slightest press.
I have used this for years now.
 

cobrajeff96

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Were you using a single catch can for that time period? I wonder if one can per bank would've made it a non-issue if that's the case. Then again a boosted setup will always require more ventilation than N/A. Maybe even twin 3/8 vents might not be enough but it's experimentation by the time boost comes into question.

I myself (Coyote N/A) run twin fully baffled cans, 12AN from valve covers to the cans but then 10AN on suction side to their normal places (closed system just like factory).
 

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RAU03MACH

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I put 2 on all mine left and right bank
When I pulled my supercharger off my cobra it was soaked with oil
And it would run like crap
Sice I put them on no problems
 
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garrittpwl

garrittpwl

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Were you using a single catch can for that time period? I wonder if one can per bank would've made it a non-issue if that's the case. Then again a boosted setup will always require more ventilation than N/A. Maybe even twin 3/8 vents might not be enough but it's experimentation by the time boost comes into question.

I myself (Coyote N/A) run twin fully baffled cans, 12AN from valve covers to the cans but then 10AN on suction side to their normal places (closed system just like factory).
I was using a single catch can. One per bank might have made it better. I kept the -8 lines that was running and ran them over to the new motion catch can. Drove 200 miles Saturday with no issues.
 

cobrajeff96

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Yea, 8AN can move a decent amount. Probably best to increase that to at least 10AN since boost, just my opinion. Again though it's one of those trial by error things. If 8AN over time fits the bill then it's good.
 

TTSaleen

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I run 10AN lines from each valve cover to a 12AN Adapter into my Moroso catch can.
Here's the can I use.

It helps alleviate the pressure in the engine (especially under boost), but it also serves a nice double duty of separating the water content running my E85.
I drain it after each drive and always get a small amount of water out of it.

Ryan
 

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