Oil drain tube sizes..what r u using?
#1
Slowest Progress Ever
![](/mt2011/images_td/ranks/supporter1.gif)
Thread Starter
iTrader: (26)
Join Date: Oct 2007
Location: The coal ridden hills of Pennsylvania
Posts: 6,028
Total Cats: 304
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
Just wondering what size lines you guys are using for your oil drain lines. I assume nothing is too big, just overkill, but what size is too small? My oil feed line to my SR20 turbo is -4 and I am using a 1/8" I think pop rivet for my restrictor, so what size I.D. drain hose should I be using?
#5
Boost Czar
![](/mt2011/images_td/ranks/supporter1.gif)
![](/mt2011/images_td/ranks/admin.png)
iTrader: (62)
Join Date: May 2005
Location: Chantilly, VA
Posts: 79,607
Total Cats: 4,102
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
With no restrictor and a -4an line I don't see how it wouldn't see over +90psi of oil pressure when you near 7000RPM.
I personally have to run a .040" restrictor with my -4an line; even a .065" orifice is too large.
#12
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
I'm using some of that water pump tubing that runs to the heater core (5/8" I think). Here's some oil flow using a -3 feed line (no restrictor) t3 center and a shimmed oil pump at ~1000 rpm idle. I've run about 500 miles since the install and haven't had any issues w/o a restrictor. YMMV
I've been looking for this video forever.
Anyway, -8 = 3/8", right?
#15
I identify as a bear.
![](/mt2011/images_td/ranks/supporter1.gif)
![](/mt2011/images_td/ranks/smod.png)
iTrader: (8)
Join Date: Sep 2005
Location: Chicago. (The less-murder part.)
Posts: 33,207
Total Cats: 6,708
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
Nominally, the AN sizes go in increments of 1/16". So -8AN should, in theory, be 1/2" ID.
That said, these is tremendous variance in actual sizing from one hose to the next, which is one reason why, when assembling AN lines, you have to be sure that the hose ends you have selected are rated as being compatible with the particular hose you are using. (variances in OD, even for a common ID, are another)
As an example, Earl's Auto-Flex has an actual ID of .438, whereas Earl's SuperStock had an ID of .5, and Earl's Speed-Flex has an ID of .563.
That said, +1 on -10. (that's looks weird to write)
That said, these is tremendous variance in actual sizing from one hose to the next, which is one reason why, when assembling AN lines, you have to be sure that the hose ends you have selected are rated as being compatible with the particular hose you are using. (variances in OD, even for a common ID, are another)
As an example, Earl's Auto-Flex has an actual ID of .438, whereas Earl's SuperStock had an ID of .5, and Earl's Speed-Flex has an ID of .563.
That said, +1 on -10. (that's looks weird to write)
#18
Slowest Progress Ever
![](/mt2011/images_td/ranks/supporter1.gif)
Thread Starter
iTrader: (26)
Join Date: Oct 2007
Location: The coal ridden hills of Pennsylvania
Posts: 6,028
Total Cats: 304
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
So my feed line is a -4 and I am running a 1/8" pop rivet for restrictor. My drain line is 3/8". My question is, will this drain line in time be insufficient and cause my seals in the turbo to blow and leak oil?
#19
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
So if 3/8
-8, am I looking at this chart wrong?
![Name: earls.jpg
Views: 794
Size: 24.5 KB](https://www.miataturbo.net/attachments/diy-turbo-discussion-14/210510d1501261221-oil-drain-tube-sizes-what-r-u-using-earls.jpg)
http://www.anplumbing.com/thread_npt.html
NPT 3/8 closest AN Ftg. Size is 8?
![Does Not Equal](https://www.miataturbo.net/images/smilies/notequal.gif)
![Name: earls.jpg
Views: 794
Size: 24.5 KB](https://www.miataturbo.net/attachments/diy-turbo-discussion-14/210510d1501261221-oil-drain-tube-sizes-what-r-u-using-earls.jpg)
http://www.anplumbing.com/thread_npt.html
NPT 3/8 closest AN Ftg. Size is 8?