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Old 16th August 2014, 04:44 PM   #41 (permalink)
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hm, really confusing then.. it makes sense to me now though.. the valve is stopping the air getting out of the crank case and thus no matter how much pressure it builds up, it can't escape.

I'll have to get back to him and find out what on earth is going on; you're right border1, it can only be breathing through the catch tank on the dip stick feed.

I'm not really that sure about fixing it though as when idle, the crankcase is typically under vacuum and then on boost, positively charged, right? This would then imply that just changing the valve over would then give me a problem in vacuum
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Old 16th August 2014, 04:50 PM   #42 (permalink)
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Do you even need the PCV in this configuration?
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Old 16th August 2014, 04:50 PM   #43 (permalink)
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Originally Posted by edizio View Post
hm, really confusing then.. it makes sense to me now though.. the valve is stopping the air getting out of the crank case and thus no matter how much pressure it builds up, it can't escape.

I'll have to get back to him and find out what on earth is going on; you're right border1, it can only be breathing through the catch tank on the dip stick feed.

I'm not really that sure about fixing it though as when idle, the crankcase is typically under vacuum and then on boost, positively charged, right? This would then imply that just changing the valve over would then give me a problem in vacuum
The previous owner might have done it to save flinging loads of oil mist down the exhaust - with the breather and catch tank off the dipstick he may have run this setup to keep an eye on how heavy the crankcase is breathing (and thus how worn the rings are, for example).

Changing the valve over shouldn't give you an issue under vacuum - if the pressure differential gets to the point that exhaust gas wants to get into the engine to equalise the pressure difference then your secondary check valve will kick in and you can carry on smiling. Looks like a fairly well setup system, bar the PCV check valve on the head itself!

Any reason why the breathing is routed this way at all? A little oil mist down the inlet never really hurts a turbocharged car!
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Old 16th August 2014, 04:55 PM   #44 (permalink)
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Matt- Maybe I don't, although what about the rocker cover outlets? Could they route air when under boost into the crankcase as they're on the same pipe?

Border1- Supposedly because nasty oil mist builds up in the intercooler and intake and he wanted to keep it shiny clean. I liked that :P

Another point I guess is, if I change the PCV valve to just a standard connector, wouldn't the oil just spray out of there or is there some baffle that only brings mist out? I don't want to empty a load of oil into the exhaust that could cause an accident.

Edit: Not sure I'd like to empty all of the engine oil out through that port either!!
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Old 16th August 2014, 05:14 PM   #45 (permalink)
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Check my pic again, my CC breathes into the sump tank which is connected to the oil cap and then to the atmospheric catch can from the rocker covers.

If your PCV is effectively acting in reverse then surely you'd be 'sucking' from the rocker and CC anyway - in which case, why not draw through your catch tank and see what you're getting? You would normally be ingesting it through the engine anyway in standard config.
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Old 16th August 2014, 05:14 PM   #46 (permalink)
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I may just get another catch can and fit it just before the one way valve so that I can monitor how much oil goes out there and then get a one way valve for the dipstick and use that as a breather for intake after monitoring whether oil still shoots out there. May not even go for the one way valve as it could be, as border1 says, a good indication of compression.
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Old 16th August 2014, 05:18 PM   #47 (permalink)
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I do like your setup Matt although I can't quite see on your car what is connecting to where my PCV valve is. Have you just plugged that up?

I've never thought about going back through the oil cap, that's pretty sweet.
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Old 16th August 2014, 05:29 PM   #48 (permalink)
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I do like your setup Matt although I can't quite see on your car what is connecting to where my PCV valve is. Have you just plugged that up?

I've never thought about going back through the oil cap, that's pretty sweet.
Couldn't tell you what's been done with the PCV as I didn't do it and the car isn't here at the moment. I'll check next time I get chance.
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Old 17th August 2014, 02:04 AM   #49 (permalink)
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Nice article.I wonder (and not using dry sump) if EVEN BETTER IDEA would be doing this graphic but instead of using the air element at the end of the air/oil separator-catch can, can be connected the exhuast venturi there to create more vacuum and "sucked" by the exhaust instead?

Or I'm missing something?

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Old 17th August 2014, 11:10 AM   #50 (permalink)
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I'm not sure more vacuum is what is needed although I'm a tad bit concerned that if I remove the PCV valve from the valve cover, I'm just going to be sucking oil out of the engine like a pump.
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Old 17th August 2014, 11:24 AM   #51 (permalink)
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I'm not sure more vacuum is what is needed although I'm a tad bit concerned that if I remove the PCV valve from the valve cover, I'm just going to be sucking oil out of the engine like a pump.
Yeah, I'd avoid replacing that PCV check valve with a straight-through adapter if I were you!

Fitting the correct check-valve and an oil-mist separator between the OEM PCV port and inlet cam cover, with a gravity drain back to the sump could work nicely, but packaging might be a bit awkward.
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Old 17th August 2014, 11:26 AM   #52 (permalink)
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Agreed!
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