Hey everyone! New to the forums and also new to turbos. I'm currently in the process of putting a turbo kit on my Miata, and have a question about the oil feed fitting. My current kit comes with a flange system, and after researching a little bit, it seems that people prefer a straight fitting into the oil feed port of the turbo. That got me looking into one.

I'm going to purchase one with a .035 restrictor on it and compare it to what came on the flange of the kit, but had a question on them.

When looking at restrictors, I saw two different types:


1.) Restrictor on the AN side of the fitting:
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2.) Restrictor on the non-AN side of the fitting:
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Besides the price, is there a difference in the performance of the two, or does it not really matter which end the restrictor is on? My flange type has the larger opening on the AN side and then the small restrictor opening on the flat flange surface.

Thanks for any help!

 

Shouldn't matter. I do wonder why you're putting a restrictor in though. Is it a BB turbo? What kind of oil pressure do you see?

 

Thank you! The reason for the restrictor is just because the kit I got for my Miata included one, so I figure that it was included for a reason. The person who puts these kits together is pretty well known in the Turbo Miata world, so I didn't want to change anything for that reason. I'm not entirely sure if its a BB Turbo, I can reach out to him and ask. All I know is that it is a clone of a Garrett T3. I haven't been able to look at oil pressure due to the engine being out of the car currently.

 

If it isn't ball bearing no restrictor should be used.

 

Thanks! I just talked to the person who puts these kits together, and he said its a journal bearing turbo. So, should I use no restrictor even if its a Chinese journal bearing turbo? I've read the replica turbos have weaker seals than something genuine, so it can cause issues without restrictors on a journal bearing Chinese turbo.

 

Use a restrictor as a last resort. Even name brand turbos leak if the drain isn't adequate, so focus on that before bandaiding it with a restrictor.

 

Thanks! My turbo kit came with a -4an feed and -8an drain. Is it true that a bigger drain is better, no matter what feed line size you are using?

 

A larger drain never hurts. -10 is usually considered a min size.

 

Got it, thanks! Is there a certain manufacturer for feed and drain lines that is recommended?

 

Search on here. There's a couple recent threads about drains. The thing I always remember is this: nobody has ever had an issue with too big of a drain, but many have issues with too small.

 

Thanks!

 

So, I just realized something. The drain fitting in my oil pan is a 3/8 NPT to -8an. Would I be okay using a -8an female to -10an male adapter with a -10an drain line? I just realized that I just put in the -8an fitting into the oil pan a few weeks ago.

 

You may be better off to use a barbed fitting to maximize the id. The drain doesn't need to be an.

 

So I ordered an oil feed fitting to go in place rather than the flange type, not sure when it will be in. Should I use a thread sealant on the threads of the fitting, or should I use a crush washer? The parts that threads into my turbo is a M12x1.25, so not sure if I should source a 12mm crush washer, or skip the crush washer and use thread sealant.

Also, should I use a metal gasket between the wastegate housing to turbo? I noticed that my kit did not come with one, but there are 5 bolt metal gaskets for sale that look like they would work with my kit:

https://www.ebay.com/itm/1407775392...aQmdbe4lWqQ-Jmp1ym5fhOMUo4j1pLgMaAkHLEALw_wcB

I was told that I shouldn't need one by the manufacturer of the kit, but I figure I should ask you all here.

 

So I ordered an oil feed fitting to go in place rather than the flange type, not sure when it will be in. Should I use a thread sealant on the threads of the fitting, or should I use a crush washer? The parts that threads into my turbo is a M12x1.25, so not sure if I should source a 12mm crush washer, or skip the crush washer and use thread sealant.

Also, should I use a metal gasket between the wastegate housing to turbo? I noticed that my kit did not come with one, but there are 5 bolt metal gaskets for sale that look like they would work with my kit:

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I was told that I shouldn't need one by the manufacturer of the kit, but I figure I should ask you all here.

 

Take a good flat file to both the turbine housing and the outlet flange to make sure they are flat and smooth. Then just bolt them together. If you want, add a little copper RTV in there.

 

Thanks! I will make sure they are nice and flat. One last question, if you don't mind. I cut down to size some of the drain line I got with the kit, and its a pretty straight shot to the oil pan. However, I noticed that the line is a bit tight and has only a slight bit of give to it. Will that be okay, or should it have more slack in it? There doesn't look to be any bends, just a slight swooping angle toward the oil pan.