Miata Turbo Forum - Boost cars, acquire cats. - 8an too small for drain line?

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8an too small for drain line?

Hey all. I'm picking out a return line for my SR20 T25. I can get an entire 8an flange,teflon line, and 3/8-NPT fitting for the oil pan for around $30. Plus I can hopefully borrow the 3/8-NPT tap that's being loaned out in the for-sale thread.

However, I've seen a lot of people saying 8an is too small. To get a 10an setup I'm looking at at least $50 and i'd probably have to buy a tap. Is 8an really too small? My t25 isn't exactly a goliath of a turbo... I'm wondering if 8an would be sufficient.

I have always run 8AN on my restricted/ball bearing garrett turbos. I am going to run 10AN on my upcoming journal bearing turbo setup.

I currently use a rubber line, 3/8" I think? Isn't -8AN 3/8" in diameter?
I run an SR20 turbo and have never had any problems with the drain. I do use a pop rivet restrictor though...

I run -8AN bung. Because Borg Warner says so.

http://www.full-race.com/articles/efrturbotechbrief.pdf

Quote:

Oil Outlet
The oil drain flange on the bearing housing has been prepared for either a paper-type flange gasket (the bolt spread is 38mm or 1.5” and the bolts are M8x1.25) or a screw-in fitting. If the port thread is selected, a fitting with a 3/8-NPTF tapered thread should be used. We recommend the white liquid type of sealant instead of Teflon tape. The oil drain line should be at least -8AN (1/2” ID). The bearing housing oil drain should be pointed straight downward where possible, and at most 20 degrees tilted right or left. When routing the oil drain line, try to keep it running downhill all the time and avoid horizontal spots or sharp bends. The oil should drain to the block or pan in a low-pressure region above the level of the oil bath. It is not recommended to install the turbo considerably nose-up or nose-down. It was validation tested to be installed “flat” with respect to the ground.

That being said I would just run a 3/8 npt barb with silicone hose -or- a welded fitting and -8AN line. I don't like screw-in fittings with AN hose because the hose is stiff, oil pan walls are thin and there are just a few threads of engagement. The stiff line puts load on the fitting and it can leak. In my case I couldn't even get the 3/8NPT to -8AN adapter to seal while my old 3/8 barbed fitting was perfect. Silicone hose is soft and very easy on the fitting.

3/8 is 6/16 is -6. Remember an is 16ths. -8 is 1/2 or 8/16.