BR's dyno testing and new parts development continues...
Jun 25, 2008, 07:38 PM
#61
In stock form, under manifold vacuum, these gases are mixed with fresh air (from the breater vent) and into the IM. Your way completely reverses this, so it's taking a much longer path to be burnt and also using a very weak vacuum source, risking more contamination, such as the water vapor that you mentioned a couple posts up. It is this contamination that the PVC system is designed to remove, using the greatest vacuum source (IM) and the shortest path to the cylinders (IM).
If all you want to do is remove the oil coming out of the breater vent to turbo intake pipe under boost, then just put an inline filter, as someone mentioned on that hose. Some people use cheap fuel filters, some people use water/air separators from compressors, as well as a number of other options.
If you want to automatically drain the oil back to the pan/block or whatever from there, that would be OK, as long as you measure any potential vacuum in the breather hose first. But I think my point here is that removing the vacuum source from the IM isn't a good idea.
Last edited by l2r99gst; Jun 25, 2008 at 07:42 PM.
Jun 25, 2008, 08:00 PM
#62
Evolved Member
iTrader: (6)
Join Date: Mar 2005
Location: Harrisburg, PA
Posts: 2,427
Likes: 0
Received 0 Likes
on
0 Posts
I thought vaccum was needed to pull the vapors out and if no vaccum is supplied, there will be excessive pressure in the crankcase. Reason number 1 I never VTA'd my lines, or else I would... the PCV especially.
I'm not worried about my intake pipe side, like I am the PCV side. My fuel filter does an awesome job between the valve cover and intake pipe. I need a new set-up on the PCV side, and I'm to cheap to buy a catch can. If it is, infact true you can safley VTA, I'll do JUST that. I'm used to oil drips. My Mirage leaks a quart of oil anytime you drive it
I'm not worried about my intake pipe side, like I am the PCV side. My fuel filter does an awesome job between the valve cover and intake pipe. I need a new set-up on the PCV side, and I'm to cheap to buy a catch can. If it is, infact true you can safley VTA, I'll do JUST that. I'm used to oil drips. My Mirage leaks a quart of oil anytime you drive it
Jun 25, 2008, 11:04 PM
#65
This is one of the points that I was trying to make. The intake manifold vacuum is what is pulling the blow-by gases, water vapor, etc, into the IM. If you unhook the PCV hose coming from the backside of the valve cover and don't provide a large enough vacuum, then you risk leaving too many blow-by gases, especially water vapor, which can cause problems in the long run.
It's called positive crankcase ventilation, because it is venting postive pressure from the crankcase (blow-by gases) which work their way under the valve cover from the oiling passages. There is vacuum in the intake manifold, which is pulling the blow-by and vapors into the IM. The fresh air comes from the breather nipple that hooks into the intake pipe. The air is 'clean' air because it is being drawn through the air filter and counted by the MAF first.
It's called positive crankcase ventilation, because it is venting postive pressure from the crankcase (blow-by gases) which work their way under the valve cover from the oiling passages. There is vacuum in the intake manifold, which is pulling the blow-by and vapors into the IM. The fresh air comes from the breather nipple that hooks into the intake pipe. The air is 'clean' air because it is being drawn through the air filter and counted by the MAF first.
Hope that makes sense...
Jun 26, 2008, 06:33 AM
#67
Evolved Member
iTrader: (8)
Join Date: Dec 2004
Location: West Chester, OH
Posts: 1,347
Likes: 0
Received 0 Likes
on
0 Posts
BTW....this is starting to turn into another confusing "theory" thread.
I went through all this crap with the Subaru and ended up buying the Crawford catch can. It sounds like it is installed the same way David installed this catch can for the Evo.
On my STI, I will say at first I didn't have anything in the hose going back to the intake, but stuff eventually started building up and I got oil in my intake, turbo and intercooler.
I personally think the system works two ways.
1. under vacuum conditions, the PCV is open and air is getting sucked through the front valve cover port, around the engine and then out through the PCV into the IM.
2. under boost conditions, the PCV closes and we start creating crankcase pressure due to blow by. But we now have a larger vacuum draw on the front valve cover port because the turbo is sucking air in. So its enough to keep the crankcase from getting to pressurized.
My vote goes for leaving the PCV setup in place and putting just the front valve cover port on the catch can and running it back into the intake.
I went through all this crap with the Subaru and ended up buying the Crawford catch can. It sounds like it is installed the same way David installed this catch can for the Evo.
On my STI, I will say at first I didn't have anything in the hose going back to the intake, but stuff eventually started building up and I got oil in my intake, turbo and intercooler.
I personally think the system works two ways.
1. under vacuum conditions, the PCV is open and air is getting sucked through the front valve cover port, around the engine and then out through the PCV into the IM.
2. under boost conditions, the PCV closes and we start creating crankcase pressure due to blow by. But we now have a larger vacuum draw on the front valve cover port because the turbo is sucking air in. So its enough to keep the crankcase from getting to pressurized.
My vote goes for leaving the PCV setup in place and putting just the front valve cover port on the catch can and running it back into the intake.
Jun 26, 2008, 06:41 AM
#69
BTW....this is starting to turn into another confusing "theory" thread.
I went through all this crap with the Subaru and ended up buying the Crawford catch can. It sounds like it is installed the same way David installed this catch can for the Evo.
On my STI, I will say at first I didn't have anything in the hose going back to the intake, but stuff eventually started building up and I got oil in my intake, turbo and intercooler.
I personally think the system works two ways.
1. under vacuum conditions, the PCV is open and air is getting sucked through the front valve cover port, around the engine and then out through the PCV into the IM.
2. under boost conditions, the PCV closes and we start creating crankcase pressure due to blow by. But we now have a larger vacuum draw on the front valve cover port because the turbo is sucking air in. So its enough to keep the crankcase from getting to pressurized.
My vote goes for leaving the PCV setup in place and putting just the front valve cover port on the catch can and running it back into the intake.
I went through all this crap with the Subaru and ended up buying the Crawford catch can. It sounds like it is installed the same way David installed this catch can for the Evo.
On my STI, I will say at first I didn't have anything in the hose going back to the intake, but stuff eventually started building up and I got oil in my intake, turbo and intercooler.
I personally think the system works two ways.
1. under vacuum conditions, the PCV is open and air is getting sucked through the front valve cover port, around the engine and then out through the PCV into the IM.
2. under boost conditions, the PCV closes and we start creating crankcase pressure due to blow by. But we now have a larger vacuum draw on the front valve cover port because the turbo is sucking air in. So its enough to keep the crankcase from getting to pressurized.
My vote goes for leaving the PCV setup in place and putting just the front valve cover port on the catch can and running it back into the intake.
Jun 26, 2008, 07:34 AM
#70
Can excessive crankcase pressure push oil from the crankcase through the piston rings and cause excessive oil consuption?
Is the only reason crankcase pressure exists because of blow by?
Would a relatively loose piston to wall gap create more crankcase pressure?
Is it plausible that the factory ports for venting are not large enough in situations like this?
What effect would 0 psi, 7 psi, and 15 psi crankcase pressure have on engine power?
What is the likely crankcase pressures of a stock Evo engine?
Is the only reason crankcase pressure exists because of blow by?
Would a relatively loose piston to wall gap create more crankcase pressure?
Is it plausible that the factory ports for venting are not large enough in situations like this?
What effect would 0 psi, 7 psi, and 15 psi crankcase pressure have on engine power?
What is the likely crankcase pressures of a stock Evo engine?
Jun 26, 2008, 08:27 AM
#71
This is where you see people talking about their dipsticks blowing out. It's due to the amount of blow-by into the crankcase during boost situations and not large enough venting to relieve that pressure quick enough.
I think the best solution for a situation like this would be to keep the existing PCV system in place and add another vent to the VC with a one way check valve only allowing pressure out...a weak one way check valve. But, that is an entirely new thread and not really what this thread is about.
Jun 26, 2008, 01:09 PM
#73
Short of running a pump, one can easily find "fast" people running bigger fittings/hoses, and even extra ports off of the valve covers of many different engines. I like David's idea, yet wonder if drilling and tapping the valve cover with larger pluming would not benefit you guys running the "big power" motors. Something David could offer as an option, if he so chose, for the people who were determined to actually need it.
