Oil Drain/Pipe fittings question - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


DIY Turbo Discussion greddy on a 1.8? homebrew kit?

Reply
 
 
 
LinkBack Thread Tools
Old 05-27-2015, 12:43 AM   #1
Newb
Thread Starter
 
Join Date: Oct 2014
Posts: 6
Total Cats: 0
Default Oil Drain/Pipe fittings question

I took a brass fitting out of my oil pan and it fits into a 3/8" brass female at the hardware store. I ordered a 3/8" NPT to -10AN aluminum adapter with which to replace it, and it doesn't fit the hole. Threads are the same, but it looks like it's about 0.5mm too thick?? I tried the Al one at the hardware store and it fit into a 1/2" compression female. Did they send me the wrong damn thing or am I missing something here? Educate me about some-a those there pipe fittin's.

Thanks!
blargh is offline   Reply With Quote
Old 05-27-2015, 12:51 AM   #2
Elite Member
 
Join Date: Apr 2010
Location: Newcastle, Australia
Posts: 2,640
Total Cats: 25
Default

Its a tapered thread so the size of the hole and the brass part depends on how far the tap was wound in and the die was would on. I'd file a slightly steeper taper on your brass and persevere or grab a tap, check that it won't hit your oil pickup inside your pan and tap a bit deeper.
nitrodann is offline   Reply With Quote
Old 05-27-2015, 12:57 AM   #3
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,797
Total Cats: 248
Default

3/8 NPT is small for an oil return. I'd do 1/2" NPT minimum. I personally ran 3/4 NPT to -12AN for a drain. IE both are 3/4" ID. What you are doing is going from 10 AN (~5/8", which is fine) to 3/8" which is tiny.

I do run 3/8" fuel line though.

If it won't thread in, threads probably need to be cut deeper with a 3/8 NPT tap to answer your question though.
patsmx5 is offline   Reply With Quote
Old 05-27-2015, 12:16 PM   #4
Newb
Thread Starter
 
Join Date: Oct 2014
Posts: 6
Total Cats: 0
Default

Thanks everyone. Woohoo, an excuse to get a new tool! I hope I can tap a larger hole (1/2" NPT as per the suggestion, then get a new fitting) while the pan is on? I've never used a tap & die set before. I'll do some reading - I know there are lots of resources floating around about oil pan tapping.
blargh is offline   Reply With Quote
Old 05-27-2015, 02:15 PM   #5
Elite Member
 
codrus's Avatar
 
Join Date: Mar 2007
Location: Santa Clara, CA
Posts: 3,878
Total Cats: 344
Default

Quote:
Originally Posted by patsmx5 View Post
3/8 NPT is small for an oil return. I'd do 1/2" NPT minimum. I personally ran 3/4 NPT to -12AN for a drain. IE both are 3/4" ID. What you are doing is going from 10 AN (~5/8", which is fine) to 3/8" which is tiny.
FWIW, 3/8 NPT isn't actually 3/8" in any dimension. The 3/8" NPT hose barbs commonly used in FM/etc kits are 1/2" inner diameter.

Blargh, if you want to read about NPT, here's a couple links:
http://en.wikipedia.org/wiki/National_pipe_thread
http://www.engineeringtoolbox.com/np...ads-d_750.html

--Ian
codrus is offline   Reply With Quote
Old 05-27-2015, 02:17 PM   #6
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,797
Total Cats: 248
Default

Well most pipe fittings, the size is the ID, that's how pipe fittings are spec'd. It's a minimum ID. Perhaps some are larger, but not all 3/8 NPT whatevers are going to measure 1/2".
patsmx5 is offline   Reply With Quote
Old 05-27-2015, 05:58 PM   #7
Elite Member
 
codrus's Avatar
 
Join Date: Mar 2007
Location: Santa Clara, CA
Posts: 3,878
Total Cats: 344
Default

Quote:
Originally Posted by patsmx5 View Post
Well most pipe fittings, the size is the ID, that's how pipe fittings are spec'd. It's a minimum ID. Perhaps some are larger, but not all 3/8 NPT whatevers are going to measure 1/2".
NPT is not "most pipe fittings", the spec is for OD because that's where the threads are. 3/8" NPT is spec'd as 0.675" OD pipe. Wall thickness varies with the material and requisite strength, but pretty much any 3/8" NPT fitting you find is going to have an ID that's much closer to 1/2 inch than 3/8. Schedule 40 steel pipe, for example, specs 3/8 pipe has having a 0.49 ID.

Regardless, 5/8" hose with a barb using 3/8" NPT threads is what most of the turbo kits out there use and it works fine.

--Ian
codrus is offline   Reply With Quote
Old 05-27-2015, 07:17 PM   #8
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,797
Total Cats: 248
Default

Quote:
Originally Posted by codrus View Post
NPT is not "most pipe fittings", the spec is for OD because that's where the threads are. 3/8" NPT is spec'd as 0.675" OD pipe. Wall thickness varies with the material and requisite strength, but pretty much any 3/8" NPT fitting you find is going to have an ID that's much closer to 1/2 inch than 3/8. Schedule 40 steel pipe, for example, specs 3/8 pipe has having a 0.49 ID.

Regardless, 5/8" hose with a barb using 3/8" NPT threads is what most of the turbo kits out there use and it works fine.

--Ian
If 3/8" pipe were spec'd for OD, and all OD's are the same, why would you call 5/8" OD pipe 3/8 NPT? That doesn't make much sense, does it?

Pipe fittings sizes are close to the ID for schedule 40 pipe. That's how the naming convention was created for pipe. It does vary depending on wall thickness, but the convention is related to ID, not OD.

Pipe = ID, tubing = OD.
patsmx5 is offline   Reply With Quote
Old 05-27-2015, 07:22 PM   #9
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,797
Total Cats: 248
Default

Quote:
Originally Posted by codrus View Post
FWIW, 3/8 NPT isn't actually 3/8" in any dimension. The 3/8" NPT hose barbs commonly used in FM/etc kits are 1/2" inner diameter.

Blargh, if you want to read about NPT, here's a couple links:
National pipe thread - Wikipedia, the free encyclopedia
NPT- National Pipe Thread Taper- ANSI B1.20.1

--Ian
From your link 2,

Quote:
Nominal Pipe Size (NPS) is loosely related to the inside diameter of Schedule 40 pipe
patsmx5 is offline   Reply With Quote
Old 05-27-2015, 07:42 PM   #10
Sadfab Union President
iTrader: (3)
 
Join Date: May 2014
Location: Kansas
Posts: 2,690
Total Cats: 113
Default

3/8 npt drain is fine. 3/8 npt shed 80 is .49 Id. You are misreading wiki again pat.
deezums is offline   Reply With Quote
Old 05-27-2015, 07:44 PM   #11
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,797
Total Cats: 248
Default

I was taught Pipe is ID, Tubing is OD a looonnnnnggggg time ago. Did it change?
patsmx5 is offline   Reply With Quote
Old 05-27-2015, 07:46 PM   #12
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,797
Total Cats: 248
Default

From here: Nominal Pipe Size - Wikipedia, the free encyclopedia


Quote:
Based on the NPS and schedule of a pipe,[5] the pipe outside diameter (OD) and wall thickness can be obtained from reference tables such as those below, which are based on ASME standards B36.10M and B36.19M. For example, NPS 14 Sch 40 has an OD of 14 inches and a wall thickness of 0.437 inches. However the NPS and OD values are not always equal, which can create confusion.

For NPS ⅛ to 12, the NPS and OD values are different. For example, the OD of an NPS 12 pipe is actually 12.75 inches. To find the actual OD for each NPS value, refer to the tables below. (Note that for tubing, the size indicates actual dimensions, not nominal.)
For NPS 14 and up, the NPS and OD values are equal. In other words, an NPS 14 pipe is actually 14 inches OD.
The reason for the discrepancy for NPS ⅛ to 12 inches is that these NPS values were originally set to give the same inside diameter (ID) based on wall thicknesses standard at the time. However, as the set of available wall thicknesses evolved, the ID changed and NPS became only indirectly related to ID and OD.
Or maybe I'm misreading something.
patsmx5 is offline   Reply With Quote
Old 05-27-2015, 07:51 PM   #13
Sadfab Union President
iTrader: (3)
 
Join Date: May 2014
Location: Kansas
Posts: 2,690
Total Cats: 113
Default

I think you've got it bolded on the end there, the discrepancy is a lot larger on smaller pipe fittings. Fittings themselves are not set to a standard either, like the I'd of hose barbs and the like.
deezums is offline   Reply With Quote
Old 05-27-2015, 07:51 PM   #14
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,797
Total Cats: 248
Default

To stay on topic, I never ran a 3/8 Drain but if everyone does that and it works, go for it. I would recommend a larger one myself as more won't hurt. I ran my GT3271 unrestricted with a 12AN drain and it didn't smoke, though I did in fact put a restrictor in down the road.
patsmx5 is offline   Reply With Quote
Old 05-27-2015, 07:53 PM   #15
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,797
Total Cats: 248
Default

Quote:
Originally Posted by deezums View Post
I think you've got it bolded on the end there, the discrepancy is a lot larger on smaller pipe fittings. Fittings themselves are not set to a standard either, like the I'd of hose barbs and the like.
True. In my experience, I've never bought a pipe fitting that I've used on my miata that had an ID smaller than what was advertised.

I run 1/4 NPT fittings on my WI and they are all .25-.3" ID brass, but a steel fitting I bought was larger ID for 1/4". Wall thickness diff. But none of the fittings are smaller than advertised in my experience. Maybe Schedule 120 would be but I've never used that on a miata.
patsmx5 is offline   Reply With Quote
Old 05-27-2015, 08:22 PM   #16
Elite Member
 
codrus's Avatar
 
Join Date: Mar 2007
Location: Santa Clara, CA
Posts: 3,878
Total Cats: 344
Default

Quote:
Originally Posted by patsmx5 View Post
From your link 2,
Emphasis is on "loosely" related.

I think what's going on here is that this is an old standard that was based on a previously-existing even older standard that's gone through major revisions over the years. Yes, at one time those numbers corresponded to physical dimensions, but at this point they really don't any more.

--Ian
codrus is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Garrett Turbo, 1.8 Oil Pan, & Misc. Stuff nbdooey Miata parts for sale/trade 9 08-30-2017 10:50 PM
OTS Bilstein to motorsports ASN conversion stoves Suspension, Brakes, Drivetrain 5 04-21-2016 04:00 PM
My solution for Oiltemp and Oilpressure input into Megasuirt (MS3) Zaphod MEGAsquirt 41 01-24-2016 01:25 PM
Moroso Air Oil Separator Catch Can Aroundcorner Miata parts for sale/trade 2 10-01-2015 04:20 PM
Low oil pressure after 1.8 swap and new turbo setup JesseTheNoob DIY Turbo Discussion 15 09-30-2015 03:44 PM


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 01:03 PM.