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I don't believe you want to use both VTA and the PCV. Perhaps it is fine if you are using manifold air pressure to control the fuel supply.
But if using vane air flow or mass air flow metering then you are sucking in unmetered air, sending you very lean.
In other words, the VTA becomes a vacuum leak when the PCV is open.
Picture form first post as described, with the separator between the manifold and pcv. When under vacuum, wouldn't the pcv just be open to atmosphere anyhow with the exhaust side vented to atmosphere? It wouldn't be able to pull enough vacuum do do its intended job.
As stated that would only work with map based fueling which i'll be running, I'm just curious as to the setup in the picture as on my reading I have seen that setup but question i's effectiveness.
Indeed, if MAP is what you will use then this VTA with PCV will work.
Your first plan is the most sensible if this is a primarily track car.
The second one offers some pollution control advantages for a street car, although the VTA nullifies a lot of that.
The second option will not clear exhaust gases out of the crankcase as well as running the exhaust side to the intake line would, since it has that continuous leak to atmosphere and will pull from that more than from the crankcase. But it will clear them out of the valve train area just as well.
But Savington and others have stated that the PCV pathway leaks a fair amount of oil during time on track, so it is best to cap it on a track car. So, back to your first option.
What's pictured there is 3/4 of a correct PCV system, only when running anything other than MAF. For what it's worth, that's what I use.
Under heavy load the PCV will close and the VTA exhaust side is just a vent. If it were plumbed back to the intake pre-turbo, it would be able to apply a little teeny bit of vac to the block. 100% PCV, or what OEMs use. You could put a second separator on the exhaust side if you wanted. Kinda pointless if you aren't running back to the intake.
I put a check valve on my intake side separator that opens at ~1psi. Theory being when the PCV is closed by boost I should be able to double the flow through the block. Any other time the slight vac in the separator closes the check valve.
My setup on my car (which is just a street car running 13psi) is just like the one from the original post SuperTuner12010 is referencing:
I used to have a check valve before the PCV valve as deezums said he does. I started getting some oil out of the breather on the drivers side that I could smell burning on the turbo manifold and the filter got pretty wet. I pulled the check valve and it seemed like it had failed and was overall pretty restrictive when I blew through it. I hypothesized that the check valve (in my case at least) was restricting the flow of air out of the crankcase when the PCV valve was open and pressure was being pulled from the valve cover. A majority of the pressure was coming out of the exhaust side and taking oil with it possibly..?
Before pulling the check valve, I had added the small air/oil separator you see by the radiator. I just left that in place since I removed the check valve and the small air/oil separator doesn't get any oily blowby in it. Just a very tiny amount of clearish fluids.
I am guessing running the setup I have now is fine for a street car. You just really don't need the air/oil separator on the drivers side.
EDIT: I just remembered that I had the baffling on the bottom of my valve cover off at one point (rock got in somehow when pressure washing the valve cover off the the car on the driveway.... don't ask.....) and maybe the valve cover didn't seal up properly? I did use RTV but maybe I will try and re seal it.
Last edited by c.buffm; 03-25-2021 at 10:45 PM.
Reason: Additional Information
My car will be a street car for the time being, but I do plan to build a motor while I enjoy the car. Aiming for a 350+whp, I am trying to do things the correct way once and not have to redo them later.
It seems the way you have it is the most common way for a daily driver. My biggest concern is the efficiency of the AOS and the amount of blow-by going back into the intake, I only have access to 91 octane so trying to do everything to minimize detonation. The benefit of complete vta can is no possibility for the blow-by to gi back into the intake. From my understanding the tradeoff is more contamination to the oil so regular 3k oil changes would probably be required.
Also looked into the slash cut on the exhaust but the only documented instances someone did it on this forum it didn't work out in the end. Would be relatively cheap though to just run -12 line from driver side vc port straight to a catch can and then to the slash cut. Then you get some vacum in theory but none of it goes back to the intake which is win-win.
I have been running a catch can between the PCV valve and the intake manifold for the past few years. The vent on the hot side goes directly into the compressor inlet. The car is an NB with an FM2, built engine running about 15psi. This is a street car, but I use boost often in the mountains. I get a ozs of oil in the can every 6 months or so. I opened up my Skunk2 intake manifold this week and found small oil pools of oil in the low point of each runner. Also, found oil film in the compressor inlet.
My single catch can is an e-Bay brand bought for $100. It intake dry for a few years, but I guess need a catch can between the hot side port and the compressor inlet. I'm considering the Dave Fab oil catch can with its two input ports and single outlet port. https://davefab.com/d062-a002-mx5-mk...oil-catch-can/ as a higher quality option that will filter both sides of the cam cover. Does anyone have any experience with this part and its effectiveness? Since it fits in place of the charcoal canister, I'm also concerned about removing the charcoal canister. Not for emissions reasons, but for the gasoline odor in the garage when parked.
Thanks in advance for any experience anyone can share.
On an NB, that canister is not the charcoal canister. It is an empty tank. The charcoal canister is a huge canister just behind the fuel tank near the RR wheel.
I think the small tank in the engine compartment is for condensation of fuel vapors to collect, so as not to have liquid fuel enter the intake; but that is my conjecture.
I have my fuel tank vented to atmosphere. Except one time when a friend over-filled the tank, and raw fuel was dripping from the vent: I don't smell fuel, but I don't have an enclosed garage. It is also my belief that a charcoal canister can only hold so much fumes. After that, they are going to VTA anyway. So, having a canister is only effective for a period of time (3 days, perhaps). If your car sits for more than that between drives, I doubt the canister (the real one) is doing much anyway.
I was pondering... I did five hard 30 minute sessions and then checked the fluid in my catch can. If we assume it's hooked up correctly for sake of discussion, what does it mean if I only got about a tablespoon of thin, black fluid? It smelled of hydrocarbons, but I could not get it to ignite.
Thanks,
Was curious if their was any new consensus on the best method for a VTA can and PCV delete. I know some people say they have done both sides vented to can with no issues on filling the can from the intake side baffle and others have had issues with lots of oil out of intake side.
I had 12an bung welded to exhaust side port and was going to tap and plug the intake side, but not sure if then it would be wise to drill a hole(s) between the intake side and center baffle to allow more air to pass or possibly cause issues. Or better to just cap it and leave the intake side baffle plate off. I know this is essentially limiting the amount of pressure that can be relieved but the single 12an is still larger than both the factory exhaust side port and pcv ports combined,
The other method would be to tap the intake side and run npt to 12an fitting as well. Only downside their is the possibility of additional oil leaking into the can but possibly not an issue with the 12an fittings and hoses and enraged holes in the baffles. I already have a single port can, but maybe summit will still allow me exchange it for a dual port can.
I did t see a reference in the thread to it, but does the orientation of the PVC valve matter? I have a 1.6 that I acquired that has the intake and exhaust sides modified with threaded fittings. I’m assuming the original builder deleted the PVC, plugged the intake, and ran a vented can. As this car is primarily driven on the street I installed a PVC back into the system and through a separator and back into the intake manifold. The PVC valve is installed in a horizontal orientation as an interrupt in the line from the valve cover to the input side of the can. Assuming the check valve function depends on gravity to seat the ball, this maybe a poor application.
My car is generating too much crankcase pressure for my current setup and venting the excess through my front crank seal. I'm planning to address this. I've read threads discussing the merits of including a check valve in the intake side of the valve cover ventilation system. I'm not sure if my planned approach will work and I'd like some feedback.
The car is a 2004 MSM that's running 14psi on a MAP tune, ~240hp. It's driven mostly on the street with the occasional track day. It's not a daily driver and gets put through it's paces when it does get out.
Current setup:
Valve cover: Unmodified
Exhaust side: Hose from the original vent tube to a breather filter in the corner of the engine bay.
Intake side: OEM PCV -> baffled catch can -> intake manifold
Front crank seal: lubricating the front subframe
My current intake-side setup pressurizes the catch can under boost and I theorise likely pressurises the crankcase via pressure leaking by the OEM PCV. Not optimal.
The exhaust side is restricted by the valve cover baffling passageways and the original 90-degree fitting press-fitted to the valve cover. This could be better.
Proposed setup:
Valve cover: Drill out internal baffle holes in exhaust side. Drill out exhaust side vent tube, tap for 3/8" NPT. Install 3/8" NPT to 1/2" barb fitting.
Exhaust side: 1/2" hose from barb fitting to a breather filter. I'm considering a VTA catch can here.
Intake side: 323GTX PCV -> baffled catch can -> check valve -> intake manifold.
Front crank seal: reseated
My theory is that by adding a check valve between the intake manifold and the catch can, the catch can should not be pressurised under boost.
Under vacuum situations, such as cruising at highway speeds, the enlarged breather should draw fresh air into the crankcase and the check valve should allow the PCV to vent pressure into the intake manifold.
Under boost situations, the enlarged breather should be enough to vent crankcase pressure.
I have pretty close to what you're proposing and don't have any crankcase pressure at 20psi though I went with a 12an outlet on the exhaust side.
On the intake side, do you currently pull oil through the catch can and into the manifold at the moment? My hose is always wet. At SMSP I'll fill a mishimoto compact can in a 15 minute session so I now just unplug that hose at the manifold barb and cap it for track sessions and just let all the pressure vent out the exhaust side. On the street its very minimal but does gunk up the check valve to the point it doesn't seal so be aware of that too.
03-25-2021, 03:20 PM
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