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Question.
Running this catch can setup on a naturally aspirated high compression (12:1) build. The ~750ml Catch can / Separator only gets an oil film covering it on the inside but no liquid worth mentioning.
Any obvious issues I'm missing ? And could this catch can setup above somehow cause excessive crank case pressure causing a leaking rear main seal ?
I've been fighting oil leaks from the rear main seal area ever since installing the rebuilt engine a year ago, transmission has been off 4 times, seals changed multiple times, crank checked and measure, rear main seal holder and half moon seal swapped a second time, .....
All OEM seals every time.
Deleted my original comment because I'm not sure it was correct.
@Stoffl If you have the outlet of your catch can forcing air back into your valve cover then I think that might cause an issue.
You might want to start another thread with pictures of your setup.
Do you have your valve cover breather hooked up to the outlet of the catch can? The arrows in your diagram make it look like the catch can is venting INTO the valve cover. That should not be the case. Both vents on the valve cover (intake and exhaust sides) allow air to flow OUT.
Your diagram should have arrows from both valve cover vents (PCV and Exhaust Side) going into the catch can, with the catch can's outlet either going to a breather (with the rest of the PCV system taken care of appropriately) or routed back into the intake manifold. I don't think I've ever heard of the charcoal cannister being involved in a catch can setup.
There are multiple ways to route this, but the diagram above doesn't look like one. FWIW, there's a video of Donut Media's Miata puking oil everywhere on track because they capped the exhaust side breather, which doesn't look too far off from what you might have setup.
I just copied the direction of "flow" from one of the the pictures in OP, also confused by it.
Yes both pcv and exhaust side vent into the catch can. Catch can is mounted in place of the oem charcoal canister, "outlet" connected to the oem purge hose leading into the subframe.
I went back and looked at some of the original posts and realized what you'd done. The explanation in some of the original posts doesn't line up exactly with my understanding, but I'm not as knowledgeable as some.
Again, you might want to just start another thread with specifics and photos for your setup.
For VVT motors, a much more complex air/oil separation system is sometimes required.
Does anyone have any insight on this, as Savington has traded cats for Miatas. I have an N/A VVT-swapped NA that sees lots of track time, and pushes lots of oil out the breather.
One reason maybe that the exhaust camber in the VVT valve cover do not have walls to slow the air flow down like the BP05 & BP4W. The early valve covers have a wall that divides the exhaust camber into two compartments with a small passage between the two. VVT valve covers are just one large camber.
For mine, I added some metal bent into a zig-zag with holes between along it to help slow the air so the oil can fall out of suspension. I still get oil mist out of my Vibrant catch can with -08 lines, but I drain the can back into the crank case.
Question.
Running this catch can setup on a naturally aspirated high compression (12:1) build. The ~750ml Catch can / Separator only gets an oil film covering it on the inside but no liquid worth mentioning.
Do you still have the PCV valve in place? Is the can vented to atmosphere? Because the way your drawing looks, the answers seem to be yes to PCV and no to vent, in which case, your system isn't really doing much. It would relieve crankcase pressure through the exhaust side/can/drain hose, but that's it.
Do you still have the PCV valve in place? Is the can vented to atmosphere? Because the way your drawing looks, the answers seem to be yes to PCV and no to vent, in which case, your system isn't really doing much. It would relieve crankcase pressure through the exhaust side/can/drain hose, but that's it.
No pcv valve. Yes the can is vented to atmosphere => "Charcoal Canister vent line going into subframe"
No pcv valve. Yes the can is vented to atmosphere => "Charcoal Canister vent line going into subframe"
Are you sure the charcoal canister vent line is big enough to vent air quick enough?
Tap a boost gauge into a spare oil cap and do some pulls. That’ll tell you if it’s excessive crankcase pressure straight away.
Are you sure the charcoal canister vent line is big enough to vent air quick enough?
Tap a boost gauge into a spare oil cap and do some pulls. That’ll tell you if it’s excessive crankcase pressure straight away.
idk but It's still a naturally aspirated engine. I doubt excessive carnk case pressure is my issue. Is was actually speculating if the venting to atmosphere could somehow cause higher oil consumption / blowby ?
Something cool I came across while researching proper air-oil separator setups. Hengst (OE supplier for a few German automotive companies) has a very cool crankcase vacuum pump with an integrated air oil separator. Best form factor I could find that can be adapted to our needs is Blue.Tron 240, part no. 181608000, intended for a (wait for it) Bugatti Chiron. Found a used one on eBay for 100ish. The main issue I could identify is that they use a LIN protocol for ECU interface/speed control, and I have no clue if anyone makes a standalone controller (or an interface module/CAN to LIN) for these. I believe someone did for the Pierburg waterpumps (also commonly found on BMWs) but have not dug deeper into this yet. Still tempted to just buy one and play with it.
Can on the firewall is run to the exhaust side VC vent, and into the air filter. The other can is off a 323 PCV to the can and to the IM.
Previously I was running a can off the PCV port with no PCV to the can, venting to atmosphere, IM plug capped. Made a huge mess at WOT on track...hopefully the 323 PCV can help with that. Also considering just blocking off the PCV port and only running the one can on the firewall.
Below is a diagram of how the catch can was set-up when I bought the car. The car is likely making around 300hp @ 22psi. I'm now using the car for spirited drives and road-trips; so a lot of highway miles and no sustained WOT. I'm considering changing the system to something more inline with the forum suggestions; at least putting the PCV back into the loop. What has me hung-up on just doing what the first post of this thread says to do is that I don't understand why the car was set-up in the way it currently is. Any thoughts? Probably appropriate for a track car, right?
I would reread this thread. What you are planning to do is putting a blockage in one of your two pathways for engine breathing when in boost. When in boost the PCV valve closes. You'll be forcing a high volume of oil vapor through one orifice instead of two and it will carry a lot of oil with it. It may also raise the pressure inside the crankcase which promotes leaks from all of the seals.
Additionally, the ingestion of oil vapor reduces the octane of the fuel air mixture in the combustion chambers and increases propensity for knock.
Track cars see a lot of WOT, so the line from the filter will create vacuum on both sides, helping with any positive crankcase pressure. That’s difficult to do if you’re not WOT all the time, so you can use the vacuum in the intake manifold during cruise or over run to do the same. Once you’re connected to the intake manifold like that, you need to keep boost from entering the crankcase with either a PCV and/or check valve. The line from the exhaust side of the valve cover to the intake pipe is still helpful when you do use WOT, so I would keep it. This essentially replicates a stock PCV system, I would just put at least the intake side through a catch can.
Thanks you two. Regarding the diagram provided, I think the piece of information I'm missing is, will the air pressure at the turbo inlet always be lower than the pressure in the crank case? My concern being with the reversal of the flow arrows. Would a check valve on the turbo inlet be sensible in that case? If it could happen.
For there to be a reversal in the compressor, the throttle plate must be closed suddenly. The intake manifold would be in a high vacuum state, minimal air would be admitted to the combustion chambers, and no fuel would be injected due to overrun fuel cut. The crankcase would be in a lower pressure state than during idle or under load and would be at no risk of overpressurization unless you had a check valve behind your air filter.
Even with a giant check valve between the air filter and the compressor inlet, it would take time to fill the crankcase through such small hoses and it would be a very brief, transient event.
In extreme applications, such as turbocharged engines operated at continuous high power on the track, it's entirely possible for the amount of blowby produced to overwhelm the capacity of the system pictured above. Remember that under boost, the PCV valve is (or should be) fully closed, so there is only one port which is effectively available to vent it. Evidence of this condition occurring is often found in the form of the oil dipstick having been pushed upwards out of its tube.
In such cases, it may be beneficial to eliminate the PCV valve (sealing the port on the intake manifold to which it connected) and instead use this the orifice for a second breather vent:
This configuration effectively* doubles the capacity of the engine to exhale blowby when operating at continuous high load. Obviously the "breathing in clean air" function at low to mid-throttle, which is made possible by the action of the PCV valve, is lost. (There is no longer a pressure differential created by the intake manifold across the valve cover.) As such, this design is inadvisable on street-driven cars with "normal" oil change intervals.
* = Actually, more than doubles. See the link below under "2:" in the valve cover notes.
I have shown two breather tanks above. If a sufficiently large breather tank with multiple inlet ports is used, then both hoses may go to a single tank.
Im confused, why would venting it cause sooner oil changes. Would it be optimal for higher power to just run 2 lines from each side to a catch can that then vents it to atmosphere. IF so why didn't mazda do that from the factory, I feel the reason is either emissions or some other reason, but wouldn't doing that be optimal for crankcase pressure?
Obviously because emissions, no civilized country allows you to simply vent crankcase gases to atmosphere. From an OEM perspective turbo builds usually have a cyclone oil separator connected to the crankcase. Pressure get's vented to the intake, oil vapors condense and get drained back into the oil pan.
figured, so would the most optimal if Im not worried about emissions be to tap both my intake and exhaust breathers to AN, and run them into a catch can that vents to atmosphere.
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