ok, so if I leave the PCV connected to the extension manifold is it ok to use the bottom nipple on the filler neck to go to the catch tank and then exit the catch tank and return it to the pan via tapping in to the oil cooler line going back to the block?

 

No, I don't think you want to do that. The oil lines are pressurized. You'll get oil being pushed into the oil can from the pressured line. The idea is just to put a catch tank BEFORE the venting line goes to its vacuum or atmospheric source.

You should block off the line going the UIM. Then take the lower nupple on the oil filler neck and go to your catch tank, and then the other end from the catch tank to your turbo inlet for a vacuum source. If you don't have the stock twins, you could use the UIM but it's not exactly the same as the turbo inlet will always be in vacuum and the UIM line will not.

 

What he ^ said. Teeing into that oil line will give a bypass around the engine's lubrication system and starve your bearings. This qualifies as VERY BAD.

 

Nevermind, I was thinking that would loop it back to the pan by sucking the oil from the can but didn't think of what would happen when the can was empty.

Ok, but you could tap in to the same line as the PVC for the return and the lower nipple of the filler neck would be the other hose to the catch tank. It may not return the oil but it should work that way, no?

Well, I just received my Custco catch tank. I ordered it because it was FD specific with a bracket but just found it it's intended for RHD is it mounts on passenger side next to brake master cylinder and won't fit with ABS.

 

Back to life... I've read multiple threads on this but can't find a definitive answer... neither for the plumbing, nor for the theory!

This quoted solution seems to me to make the most sense (and be the simplest) -- adding a baffled oil catch tank ("oil separator"?) between the filler neck and the pre-turbo intake. But I assume the tank would have to be vented with a filter, so as... not to... create... too... much vacuum in the oil pan (via filler neck)... ???

But, what would one do with the existing (oem) hose that goes to the filler neck? Keep that there? I understand that to go via the pcv valve to the UIM.

So could one theoretically just tap another line into the oem filler neck and run it to the catch can? (or tee off the existing hose)

I'm looking into this as I have what seems to be a lot of oil in my entire intake system... everything from air filter piping to BOV piping to intercooler. There's always a little pool and coating of oil when I take off the hoses on my intake system, and even though I know it's fairly harmless, I don't like always having to clean it up!

(alternatively, is there another possible explanation for this??)

Thanks!!

 

There's 2 ways to do a catch can.

You can have a can in-line with the factory hose. This will catch the oil and keep it out of the intake. It's also the emissions compliant way to do it - any vapors that the car emits, per emissions regulations, have to be burnt by the engine and scrubbed by the cat. So, vapors from oil fill neck to catch can to primary turbo inlet duct.

The second option is to do a vented catch can. I have a Jaz mini catch can that has a small filter on the top of it. You have the line from the oil fill neck run to the can, oil and vapors collect in the can and it can breathe due to the filter up top. Not emissions compliant since you're letting potential emissions out of the system.

On my setup the catch can has 2 inlet nipples, I have a line from each of the 2 oil fill neck nipples going to the 2 on the can. I clean it out at every oil change, been really happy with it.

If you are doing hardcore track work the catch can setup gets weird. That's an entire other topic. For a street car, one of the 2 options above will do the trick to keep the oil mess out of the intake plumbing.

Dale

 

The FD has two methods for relieving crankcase pressure. If you are operating at vacuum, crankcase vapor is sucked into the throttle body from the oil filler neck via the PCV ("Passage 1" below). If you are under boost, the crankcase pressure is "pulled" into the primary turbo ("Passage 2"). The problem with the second is getting oil in your intercooler, hence the catch can between the filler neck and the primary turbo.


I followed Rob Robinette's instructions and capped the PCV.

https://robrobinette.com/pcv.htm

I also did not vent the can. I found at the track i was emptying the catch can after every session. It was a smaller can, but still???

I since upgraded to a baffled oil fill neck and larger (1 qt catch can).




I also installed a blingy oil cap. Problem was the cap had a plug in it. This ended up blowing out and spraying oil all over my engine bay.



So, it appears the crankcase pressure is more than the "system" can handle (pulling the vapor into the primary turbo). I now have the catch can vented to the atmosphere (the can came with a filtered cap), but still in-line between the filler neck and the primary turbo. Now i can go a full weekend without having to empty the can.

 

Mazda removed the PCV valve on the 95 cars FYI. I don't think it's necessary to have.

For a street car getting a catch can working so you don't have oil mess in the IC is pretty straight forward. For track cars it's a WHOLE different thing.

Dale

 

So long story short, I just run the catch can in-line on the hose that comes out of the filler neck -- which won't be as effective as an oil separator with a filter, but should still catch a bunch of oil?

 

You are correct.

Dale

 

Updated if you are interested:
Triple-R: Catch Can Part Deux

In short, much bigger can and bigger vent line from the oil filler neck only. Run oil level 1/2 qt low when on the track.

regards,
crispy

 

Dude you should try to make a few of these oil catch can, there is none in the market now that can compare to youe setup. If u do have an extra one to sell lmk I would buy it.

 

What about tapping the front cover and let the catch can drain in there with a check valve so it doesn't flow up?

 

Sorry to bump this, but ive read few threads about what to do or where to route both or single nipples from neck, but nothing about what to do or use the big nipple left on the UIM? Does that just gets capped? or what can it be used for?


Asking because i have a single turbo one that ive had for a long time and it has a little hose with a check valve to the uim from the top nipple, then the bottom nipple is routed to the vapor line to the canister..... Im guessing that is being used as catch can? ive thought about adding a catch can, but have never really looked into it till now , specially wondering when the check valve could fail or if it already has and idk lol.

 

Cap the nipple. You don't need it.

Use a proper cap of some kind, EPDM rubber nipples from McMaster-Carr work. Stuff from the parts store will probably fail in a week. You want to clamp it on tightly too, since it's such a large cap it's very easy for that to be a leak point.

Dale

 

the catch can is mounted next to the alternator, it has a small filter on the vent

This was custom made by Adam Griffith, whose handle on this forum I cannot recall at the moment.

Recently I modified it to add another hose from the oil filler to the can. Space is tight, and the hoses are small.

I also changed the drain to the block from a relatively small hose to -10. It drains into the stock turbo oil return, with heat shield near the turbo down pipe.

 

Did you find you need a check valve to the drain to TT oil drain? I'd heard of other using that like in attempt to add a second pressure release point in the pan, only to find it filled the catch can MORE.

I was looking at setting up an air/oil separator tank, with check-valved line to the TT drain, and then an overflow to a vented catch can.

 

I found a huger amount of oil in intercooler, air box and the hoses. I cleaned everything and decided to install a non-vented (sealed) catch can with two connectors. It's a 1999 model, so no PCV and stock twin turbo. As I understand The catch can has to be connected before the primary turbo and the blind spot at the oil filler.
I think of installing the can somewhere near the break booster, but have no final decision yet. What do you guys think of this idea?

 

theres no reason to install a catch can in your all stock car.

the routing of the lines for a non vented can will be one from the turbo inlet to the can and from the can to the oil neck.

 

Whatever location you can fit the can is a good location
Not much room