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Discussion Starter #1
I've been researching all morning on the difference between AN and NPT. I have found sizing charts and so forth but nothing tell me what would be a solid way to determining if your fitting is AN or NPT. I'm trying to find an oil restrictor for my Turbo but I cant determine if its AN or NPT and I have to order this over line as no parts store has this item available... Can someone tutor me on the difference between AN and NPT? How to determine if it is AN or NPT?
 

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I've been researching all morning on the difference between AN and NPT. I have found sizing charts and so forth but nothing tell me what would be a solid way to determining if your fitting is AN or NPT. I'm trying to find an oil restrictor for my Turbo but I cant determine if its AN or NPT and I have to order this over line as no parts store has this item available... Can someone tutor me on the difference between AN and NPT? How to determine if it is AN or NPT?
what turbo do you have?
 

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AN fittings have a 37* taper, the threads are straight, and generally use o-rings.
NPT fittings have a 45* taper, the threads are tapered (harder to turn as it is tightened), and you will have to teflon or industrial sealant.
 

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This is a good pic showing the difference.
This is conversion fitting, it is 1/4" NPT on the left side, and -4 AN on the right.
Note that the inner diameter is the same through the fitting.
The NPT thread is bulkier, and there is not a large taper on the end of the fitting.
The AN thread is leaner, there is room for an O-ring, and the end is tapered at 37*
 

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AN fittings have a 37* taper, the threads are straight, and generally use o-rings.
NPT fittings have a 45* taper, the threads are tapered (harder to turn as it is tightened), and you will have to teflon or industrial sealant.
hazzah! I was just going to mention that but I read your post :up:
 

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hazzah! I was just going to mention that but I read your post :up:
Yeah, fittings can get really confusing lol.
My friend is a maestro at that stuff, he can look at something from 10 yards away and tell you the size and type :silly: He makes industrial hydralic/oil/fuel lines all day though.
 

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Discussion Starter #7
Wow you all are awsome! I have a greddy td06l2-20G. I just measured the fittings that was in it and the one that fits IN the CHRA, ISNT tapered. In fact it looks like the picture noted above by signalpuke with the NPT side going into the turbo and the AN on the oil line. I used a micrometer and found the size are .384 on the NONE tapered side (the side that fits in the CHRA) and .430 on the Tapered side (the side on the oil hose).

So am I looking for a 4 AN Male to 1/4 NPT .60 reducer male??

Or what is the correct size of the fitting I'm looking for corresponding to the decimal measurment I supplied??
 

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the fittings for the oil inlet on a Mitsu turbo are machine thread I do believe. when I was trying to get the right fitting for a 14b from Stealthmode Performance they told me that there are 2 different threads on the Mitsu turbos.

That was about 3 years ago, so I may be mistaken. check on the Stealthmode website.
 

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Discussion Starter #9
yeah I got through to greddy tech support and they verified its 1/8 NPT, is 1/8 NPT slightly smaller than a 3 AN? I need to find a Male 1/8 NPT to 3 or 4AN fitting, I just need to figure out the size of the AN side now...
 

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Discussion Starter #10
I could just buy APT's 1/8 NPT .06 restrictor and intall the current 1/8 NPT to 4 AN or 3 AN straight fitting that I have. HOWEVER I'm getting ready to install an oil pressure gauge and i'm wondering if i can us a T off the oil feed like to the turbo as a port for my sending unit while I'm at it..
 
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