So after reading a bunch of conflicting views it seems as though a setup similar to Aaron (mannykiller) is a decent place to start.

ie:
-6AN from UIM to oil fill neck with inline check valve.
-8AN from fill neck to catch can.
(Then lots of debate about running a line from the rear turbo drain + line from turbo inlet to catch can)

I question the ability of the -6 line with check valve to be effective under boost unless there is some sort of amazing Venturi effect.

Also wouldn't the -6 create a massive vacuum leak at idle as you are tapping the UIM after the throttle plate and venting it to atmosphere (he runs a vented catch can)?

 

- A line from the rear turbo drain will help the setup by allowing both sides of the motor to "breathe"
- The UIM line only works under vacuum, not boost. That's why you use a check/pcv valve.
- Vented or back to the turbo inlet is personal preference, during boost when the UIM line is not doing anything is when the vent or turbo inlet will work. The turbo inlet may cause all the intake system to have an oily film.
- A proper PCV valve won't create a vacuum leak.

 

You are essentially drilling a hole in the UIM and installing a valve that lets air in but not out. Then running that to a can that is vented to atmosphere. Vacuum from the motor will be sucking crankcase vapor in at idle...but it seems it will also be sucking in atmospheric air via the catch can.

 

One BIG BIG factor here is what are you doing with the car. Street driven? You just need a super basic setup, search around on my Jaz catch can setup, I've written it up many many times.

Street with some track events? Probably a basic setup, maybe just have to empty it more often at the track.

Dedicated track/drift car? That's when you need to get medieval.

Dale

 

Good point Dale. Should have clarified this is for a dedicated time attack car.

 

Mazda drysump will fix it.

Trap door baffle oil pan will get you 90% there.

 

Track day car here with BNR twins. I'm running an IRP filler with the AN-10 bung to a Moroso catch can. Works very well.

 

Can confirm, the vented UIM vacuum source will essentially be a vacuum leak if you use a just a check valve. My idle was very high, also, im not sure why but there was a ridiculous wailing noise from my setup. I used the same hole the original PCV was connected to.

I think an actual PCV valve is closed at idle and opens incrementally during vacuum.

I ended up running an identical vented can setup, with a 10 AN line from the filler to a Vibrant catch can. I am on twins and running 20w-50. It caught a crazy amount of oil, probably 1/3 of a liter each 20 min HPDE session. I spun a couple times and that dumped even more oil into the can.

 

Dry sump would be the dream. I have a Built 2 Apex baffled pan with trap doors for now.

 

Thank you for this. I was really confused how that setup wouldn't screw with idle.

Here's the exact video I was referencing.

 

The Radium PCV valves I mentioned above don't create a vacuum leak, the are closed at idle but open with higher vacuum

 

Oh nice. Thank you for that.

 

Oh that's interesting. So he's running the Radium Catch Cans in a closed loop with a PCV and that prevents as much oil being spat out of the pan vs just a vented catch can setup?
Or am I misunderstanding and he's got a PCV on the oil filler neck to the UIM, but then also a line to vented Radium Catch Cans?

If it's the later, it doesn't make sense to me since then, any type of vacuum from the UIM would be lost through the vented catch can first, negating that suction effect.
If it's the closed loop with a PCV, during boost, there would be technically NO venting of the crank. The PCV is closed and the can itself is closed, unless there is a return to either the UIM or the turbo inlet. The stock system utilizes the vacuum from the primary turbo inlet in that scenario but not sure how his setup deals with this...

 

I'm not following the whole "closed at idle but open under vacuum" thing. Idle IS vaccum... the only instances I can think where you have more vacuum than at idle is decel.

I also am surprised it matters in terms of lessening the amount of oil in a catch can, since wouldn't the big pressure buildup be under boost when whatever type of valve you had going to the UIM is closed anyway? And, didn't the 94+ cars eliminate the PCV altogether? I'm just struggling with what the dynamic is here that would actually prevent lots of oil in the catch can. Aaron's system just replaces the 2nd line to the primary turbo (which wouldn't be vaccum, just atmosphere), with a line to a catch can (presumably vented to atmosphere).

That said, it would be easy enough to try with the OEM PCV Valve run off the extra NPT fitting on most aftermarket filler necks.

 

Correct. He has a follow up IG reel that clearly shows the can is vented.

He swears he can do a full day of drifting with minimal oil in his can...

If it's true I am not understanding how/why.

Assuming the check valve doesn't create a big *** vacuum leak at idle, and it is providing PCV vacuum...it is closed under boost (Arron suggests maybe it is open under boost due to Venturi effect).

The issue isn't excessive blowby at idle.

Under boost it seems his system would be no different than running just a single line from the filler neck to vented can (which he says he tried and was having to empty his can multiple times throughout an event and only after the addition of the check valve to UIM did it resolve).

I actually ordered the check valve and fittings, was about to weld them on and thought...wait a minute ?.

 

I think it makes sense for NA engines with closed loop PCV setup. As rpm increases you would see less vacuum, but you would also have increasing positive pressure from the crankcase.

 

To be completely honest, I also don't understand how 13bs develop "crank case" pressure. Other than the oil pressure regulator and pick up tube, our oil pan (crank case) is completely isolated from combustion and the e-shaft. for me personally, I saw literally NO oil in my catch can during tuning and street driving.However, on track, i was dumping possibly 1/3 of a liter per 20 min session, and i think its more due to Gs on sustained right handers forcing oil up the fill neck. Before I had a vented catch can and baffled filler neck, on the Robinette in line PCV setup, I would end up dumping oil all over the driver side of the engine during track

 

using exhaust scavenging to pull the pcv gasses out could be considered as discussed here: https://www.rx7club.com/rotary-car-p...haust-1158978/

compression blow back from side seal clearances and oil control rings can create pressure and oil fuel dilution

 

It's really the same as piston cars - engine oil gets hot, the oil aerates, lots of things whipping up and getting hot - that means expansion. The oil pan will pressurize if it's not vented and pressure will find a way out.

Dale