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Old 07-23-2011, 06:47 AM   #1
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Crankcase Pressure....Bypass Valve Question

So this year my PCV Oil Sep is collecting far less oil than in the past years and I have a theory..?

My setup is PCV run through Oil Sep and a breather on each valve cover..(I know that setup can cause a debate about vaccuum leaks etc-but that is not the point of my question)

Pic of setup..oil sep can be seen in top left corner




Only difference is this year I switched from the 6 inch K&N air filter that came with my Vortech kit years ago to a Widemouth UPR 9 inch filter..see pic





Is it possible the larger air filter is allowing the bypass valve to work more efficiently and decrease crankcase pressure...? which has decreased the amount of oil collected in the Sep..?
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Old 07-23-2011, 10:15 AM   #2
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If it effected it at all(I don't think it does)I'd think it would do the opposite since the larger filter would more than likely let it breather easier!!! Just coincidental IMO!!
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Old 07-23-2011, 01:56 PM   #3
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Unless my logic is incorrect....the larger filter allows the engine to breathe easier; therefore there is less crankcase pressure and less oil being pushed through the PCV/oil sep..?
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Old 07-23-2011, 03:40 PM   #4
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What you are saying could be happening, but I would think that you are allowing the engine to breath easier on the wrong side of breathing if that makes any sense? It would seem that it would allow more air into the motor, inturn causing more crankcase pressure. That is just the way I would imagine it working, but I could be wrong. If it is working the way you say, that is pretty neat! I am about to purchase a new filter for my setup and planned on going as big as I can, but I was going to do that to allow the supercharger to breath as easily as possible. If it works out your way, it is just another reason to go big! Either way it is interesting that took place.
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Old 07-23-2011, 04:05 PM   #5
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For some reason i don't think so. Pretty much i think the blow by air is just getting circulating back into the supercahrger not really going out the air filter. If it is doing that something would be going on with the stock ecm, that is why u don't vent the bypass valve to atmosphere. I see nothing wrong with your set up with the pcv.

If it working the way u said i would just vent the bypass to atmospher instead of going back to the supercharger and that should let it run cooler.
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Old 07-23-2011, 09:16 PM   #6
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But If hes running a draw through style meter doesnt he have to recirculate the air back and not vent to atmosphere? I was always told if you vent to atmosphere you have to run a blow through style air meter.
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Old 07-23-2011, 11:20 PM   #7
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^^^Yeah, I was told the same thing. The car won't run right if you vent air that has already been metered by the MAF.
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Old 07-24-2011, 11:46 AM   #8
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The air intake filter has nothing to do with the PCV system. The same amount of air is in the crankcase regardless what size filter you have as it is metered.

If you add breathers to the valve covers, this will give the crankcase a way to relieve the pressure. But then when it's running N/A you create a vacuum leak... The upper intake will suck air from the crankcase via the PCV valve. As the air gets sucked from the crankcase, it needs to be replaced. It will take that air from the breather caps, suck it into the crankcase, through the PCV, and into the upper intake... Thus introducing unmetered air into the engine...and that is bad.

A solution... remove the PCV system and convert it to a Breather type setup. To do this, remove the tube that connects the oil filler tube to the TB and cap it off on the TB side. Take the oil filler tube side and vent it to the atmosphere (or replace the entire valve cover and just pop on a breather instead.) Take the tube that connects the PCV to the upper intake and disconnect it from the upper intake. Plug the nipple on the upper intake side and let the tube (which is still connected to the PCV valve) vent into the atmosphere as well. Now add a breather to the opposite valve cover. A lot of times, people will place this tube right next to the filter on the inlet side of the supercharger. That helps reduce the smell of fumes in the engine bay and passenger compartment.

There is another method that some people seem to use successfully. It involves leaving the PCV system connected but actually running an open breather. Like I said above, that creates a vacuum leak. But some argue that it is a very small vacuum leak and you can tune around it by slightly enrichening the mxture to compensate for the vacuum leak.

To do this, you need to make a few changes. First, get a nice fresh PCV valve. Look for one off an old 4 cylinder turbo Mustang because that one is designed for boost. If you can't find that, then you can get one for a 1995 Toyota Supra which was also boosted. Just be sure to get the grommet for it too. You will also need a check valve. The cheapest way is to just get a brake booster valve.

Once you have those parts, install the new PCV in place of the old one. Then, take the check valve / brake booster check valve and place it in the middle of the vacuum line that goes from the PCV valve to teh upper intake. When in place, it should allow air to flow from the crankcase. But when pressure is applied from the other side it will prevent any air at all from getting by and into the crankcase. Now get a single open-element breather and drop it on the passenger side valve cover. By doing this, you let the PCV still suck gasses out of the crankcase during normal operation. And when you hit WOT, the check valve and new PCV slam shut to protect the crankcase while any blowby will easily be blown out the breather cap.

Looking at a standard PCV diagram usually helps to see what it is designed to do.

Update for me: I have went to baffled valve covers with AN fitting, moroso vented/baffled catch cans, and a T-Bird SuperCoupe PCV valve (no other check valve needed then). TB is plugged.
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Old 07-24-2011, 12:29 PM   #9
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Quote:
Originally Posted by JP_Stang View Post
^^^Yeah, I was told the same thing. The car won't run right if you vent air that has already been metered by the MAF.
I am just saying u will get reversion of air (flowing back through your meter) and not sure what the mass air flow meter will do with the signal it generates from that. I am running speed density and got mine bypass vented to atmospher.

Pretty much not sure why u have less oil collected in the seperater. From a bigger air filter??? Did u see more BOOST???
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Old 08-23-2011, 08:30 AM   #10
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My Theory was all wrong-forgot to post this up .....!!!!

Turns out the drain to my Oil Sep was slightly open and creating a vaccuum leak so it was not working properly....

-----------------------------------

To the ? about more boost...Yes I saw 2 more psi with the big mouth filter...I am seeing 12 psi with a 3.33 blower pulley and 6.87 crank.
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