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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 ?
03-21-2024, 12:07 PM
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