sevenracer Reader
12/26/21 3:24 p.m.

Trying to sort out something on my rx7 TII swap.

I need to connect up the turbo oil drain. The original stock oil drain line was cut and I need to connect that to a modified 12A front cover that has a 5/8" barb fitting.

So, I planned to just use a length of hose, but though the original pipe has a flex section, the angle is still poor and the hose is kinked a bit.

My question is, based on how small the supply feed is to the turbo, it seems link the drain hose, even if it is moderately kinked, should still be plenty to drain. Am I missing something?

Other options are to find an anti kink coil to slide over the hose or I have a brass elbow that I could JB weld into the end end of the stock line (pic below). I couldn't find a steel part to weld in, plus I don't think I could weld it or braze it oil tight myself.

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
12/26/21 3:37 p.m.

I'd prefer to see 3/4".  It does make a difference.  5/8" is probably okay if it is all downhill and there are no kinks.

Turbos do not have "seals", they have labyrinth things that rely on centrifugal force from allowing oil in the center housing to escape into the outside world.  The flip side of this is they will happily allow air IN under pressure if it wants to.  The two-part upshot of this is that the oil that comes out of the turbo gets whipped up into froth and is much larger in volume than the oil that went in, and because there is no positive sealing, if the oil backs up into the bearing housing it will get past the seals and smoke a lot, because the labyrinth seals do nothing if they are "submerged".


edited because I thought I was looking at something else.  T2 swap, durr, not an old BAE or Cartech setup for the 12A

Streetwiseguy MegaDork
12/26/21 3:39 p.m.

You want to make sure it drains well.  It's pressurized in, not out, and it's pretty easy to overwhelm the seals, at least on older turbos.  That may not still be true, but the oe's still make a nice straight large drain tube.

wae UberDork
12/26/21 4:49 p.m.

I had all sorts of oil-blowing-everywhere-under-boost problems that went away when I took the slightest bit of a low spot out of my turbo's oil return line.  I would opt for as little resistance as possible for your return.

1SlowVW HalfDork
12/26/21 6:41 p.m.

Why not just put a bung in the oil pan? Then you could have more drop and less angle. 
Seems like an easy fix while the motor is on the stand. 

preach (dudeist priest)
preach (dudeist priest) GRM+ Memberand Dork
12/26/21 6:49 p.m.

In reply to 1SlowVW :

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
12/26/21 6:51 p.m.

In reply to 1SlowVW :

One rule of turbo drain club is that they should not drain below oil level if at all possible.

sevenracer Reader
12/26/21 6:56 p.m.

Ok, frothy oil, makes sense. Thanks all.


1Slow - I agree adding a bung to the oil pan would be easier now than it will ever be, but I really was not wanting to pull the oil pan and definitely not the front cover if I could help it.


1SlowVW HalfDork
12/26/21 7:04 p.m.
Pete. (l33t FS) said:

In reply to 1SlowVW :

One rule of turbo drain club is that they should not drain below oil level if at all possible.

The oil level is going to be the same wether you dump it above or below. I've dumped into the pan on 3-4 set ups without issue and I'm sure one was under the resting level of oil in the pan...but I still had 4" of drain line above where the level would be to the turbo. 
I realize for a track car that may be adding another point of failure...but if it's all welded and braced well I wouldn't loose sleep over it. 
I can't say I'm familiar with rotaries and there oil pans so take my advice for what free advice is worth. 



sevenracer Reader
12/26/21 7:31 p.m.

Well ok, so Summit Racing has a wide selection oil drain flanges with AN, or barb fittings. Surely, one could fit a stock TII turbo.


And an outfit called B1speed offers a turbo oil line kit for an FB swap. This may be the easy(ish) button, though a little spendy since I don't need the supply line.

Terrible picture from their site, but it looks like the bung gets added to the 12A front cover on the angled surface below the metering oil pump:


Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
12/26/21 7:44 p.m.

In reply to 1SlowVW :

That was per MacInnes' book, and he is one of the people who engineered journal bearing turbochargers like the old Hitachi sitting there.

Yes I know VW drains to the bottom of the pan on the 1.8t.  They do a lot of weird things smiley

The theory is sound though... trying to drain foam into an outlet blocked by solid oil is not the best policy.  Maybe the K03 turbos had really good seals, or maybe VWAG heavily restricted oil flow, or maybe they figured that the drain was long enough that it would sort itself out when it got there.  They WERE adamant about not having the oil even one mm higher than the full line.


It should be noted that on a 12A type pan the oil level is almost at the pan rail.  Anywhere you can add a bung is going to be under the fluid level.  The additional fun is that the inner tie rods come extremely close to the pan at full lock, so there is not much actual room to put anything on the side anyway.  

1SlowVW HalfDork
12/26/21 8:12 p.m.

In reply to Pete. (l33t FS) :

Ill have to dig up a copy of that book . You're right vw does some weird stuff and so do the people who modify them :p 
Sounds like it going to be a right fit either way. I wonder if you could get a nice smooth bend with tubing and use a piece of hose just at one side for a flex. 


That kit could easily be reproduced by a fitting shop if you bring them your old turbo fitting and the one on the block. That's probably where I would start. 

ShinnyGroove (Forum Supporter)
ShinnyGroove (Forum Supporter) HalfDork
12/26/21 10:34 p.m.

Straightest line possible, all downhill with no obstructions.  I wouldn't feel good about anything with a kink or a low spot before the sump.  It's possible to drill the oil pan in place and put a -AN drain in, if you're careful.  Miata turbo guys do it all the time.  Basics:

- smear the drill bit with grease to pick up any metal shavings

- mark the drill bit so that it only goes through the wall of the oil pan; you don't want to run it in too far and hit the oil pickup

- after drilling, reach into the hole with your finger and fish out any metal flakes you can find

- clean all oil and dirt away from the drilled hole and use JB Weld to seal the -AN fitting in place.  I've done several this way and never had one leak

RXBeetle Reader
12/26/21 11:09 p.m.

I'm running a very similar setup, 13B with a 12A front cover. I welded a 1/2NPT bung in the cover but it's not far off your location. I have a real sharp miter cut kink off the cover bung and a short hose back to the turbo drain elbow. The tubing is "beverage" thin wall stainless and the hose is high temp aeroquip and hasn't been an issue. It is all 3/4" and I don't think I would go smaller though.

sevenracer Reader
1/1/22 10:32 a.m.

So, I ended up cutting off the flex portion of the stock drain tube and using 5/8" hose. The stock piece has a nice 90 off the flange and a little heat shield facing the turbo. I bought a vibrant adapter flange but the diameter was way smaller than stock, so I didn't use it. I'm pretty confident this will do the job. 

This is the vibrant adapter VS stock:

codrus (Forum Supporter)
codrus (Forum Supporter) GRM+ Memberand PowerDork
1/1/22 10:53 a.m.
ShinnyGroove (Forum Supporter) said:

Straightest line possible, all downhill with no obstructions.  I wouldn't feel good about anything with a kink or a low spot before the sump.  It's possible to drill the oil pan in place and put a -AN drain in, if you're careful.  Miata turbo guys do it all the time.

Miata oil pans are quite a bit different from rotary oil pans.  Cast aluminum rather than steel sheet metal, and there's several inches oil pan wall above the sump level in which to mount the bung.


93gsxturbo UltraDork
1/1/22 11:46 a.m.

Make sure that hose is temp and oil rated, I used some air line once on a build because it was color matched (what can I say I was 19) and it blew out at a very inopportune time.  Long story short I went into someones yard in the middle of the night, cut a section out of their garden hose, patched it up, drove it 800 miles home.  

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