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Old 05-31-2007, 02:21 PM   #1
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Default T25 Oil Restrictor (Need Opinions)

I'm in the process of sticking a t25 on my '92 NA and am to the point where I'm running oil and water lines from my distribution block to the turbo. Right now I have a -an to i.f. adapter in the oil supply port of my turbo. I would like to simply run ss braid line to my turbo and that be the end of it. I don't really like the idea of putting two more connections in the oil supply line just for the restrictor.
So I have an idea of simplifying the restrictor setup, but I also have two questions....

My first quesion: Should I should I not put an .060 restrictor in my supply line? I know some people get over oiling problems without the restrictor, but is under oiling a worry? I know these puppys don't require much oil flow to supply the bearing, but I just need some extra reassurance from the experienced.

2nd question: If I come to the conclusion that a restrictor is necessary, does anyone see a problem with TIG welding the end of my -an to i.f. adapter solid and just drilling an .060 hole in the end that is welded, so i don't have to connect a restrictor fitting inline? I can always drill the weld completely out if i want to remove the restrictor.

Thanks for taking the time to read my question!
Anthony
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Old 05-31-2007, 02:37 PM   #2
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just do the pop-rivet trick....search Samnavy's post about it. should get you to .125"
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Old 05-31-2007, 03:55 PM   #3
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Is the turbo a newer Garrett ball-bearing turbo or is it sleeve-bearing?

I sure as hell wouldn't just throw a restrictor in it without doing some more research than it sounds like you've done. The turbo will survive over-oiling for a short while...dunno how long it'd survive with too little oil. Besides, it'll be more difficult to tell if it's under-oiled than if it's over-oiled. Over-oiled, it'll smoke...put in a restrictor. Under-oiled, it might make some nasty noises or not spool up quickly? I don't really know.
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Old 05-31-2007, 04:17 PM   #4
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I have brought up the use of 1/8" alum rivet restrictor and did a little testing before I ran with it. I now don't even use it because my turbo doesn't smoke any without it. I would try without the restrictor first, then if it starts smoking introudce the restrictor.
The inside hole of a 1/8" alum rivet is .075 which is close the restrictors sold for turbo (.060 or .030 for BB).
Check out this link for the results of my testing. I saw a drop of 7psi at the turbo with the restrictor both at idle and high rpm.
https://www.miataturbo.net/forums/sh...5&postcount=14

EDIT: Here is the orig Samnavy thread where this was all discussed. https://www.miataturbo.net/forums/sh...ivet+1%2F8
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Old 05-31-2007, 07:39 PM   #5
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If you have a -4 or larger line you might want to use a restrictor. FM uses a -3 line with no restrictor and no problems on hundreds if not thousands of cars, even with BB turbos. That is what I have on my car.
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Old 05-31-2007, 07:46 PM   #6
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Quote:
Originally Posted by Mechazawa View Post
If you have a -4 or larger line you might want to use a restrictor. FM uses a -3 line with no restrictor and no problems on hundreds if not thousands of cars, even with BB turbos. That is what I have on my car.
Just to add. Many BB turbos have built in restrictors.
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Old 05-31-2007, 09:08 PM   #7
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Quote:
Originally Posted by Mechazawa View Post
If you have a -4 or larger line you might want to use a restrictor. FM uses a -3 line with no restrictor and no problems on hundreds if not thousands of cars.....

+1 from eveyone's experiences here as well....
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Old 06-01-2007, 12:58 AM   #8
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I recommend using them if you use a -4AN line. I have a few of the -4 fem to male .060 restrictors in which is what i use.
-Michael-
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Old 06-01-2007, 01:06 AM   #9
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Bandit, where'd you get that -4AN female to male .060 reducer? Any chance I can swipe one off of you for a few bucks?
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Old 06-01-2007, 01:19 AM   #10
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Actually, i'm running a -6an supply line because thats the only adapter size I could find out of the block. I ordered it from earls before I knew about anplumbing.com. Also, I have done some research on it and have found from brain's faq that .060 is the recomended size. My turbo is a non bb t25.
I did see the pop rivet trick, but I don't really like it. I have a tig welder and would rather just take 2 seconds and weld the tip of the fitting closed. And drill it out.

As suggested, I'm going to try first without the restrictor and see how bad it smokes, but since I'm running -6an supply line I'm anticipating that I will have to restrict it some....

Thanks for the help guys.
Anthony
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Old 06-01-2007, 06:48 AM   #11
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Is FM still selling the -3 size line kit?? I didn't see it on their site....
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Old 06-01-2007, 11:52 AM   #12
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Okay...so you know your turbo is not ball-bearing.

You also know that, in general, the newer Garrett ball-bearing turbos sometimes require restrictors when using -4AN feed lines.

How are you jumping to the conclusion that your non-ball-bearing, older, T25 needs a restrictor?

Okay, I just read that you have a -6AN feed line...now that we've got that part of the puzzle, I would say you probably need to bring that down to ~ -3AN or -4AN. That's 3/16" or 1/4", but bringing it down to .060" w/o knowing for certain it requires that little oil seems really dumb to me. That's a far cry from 3/16-1/4".
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Old 06-01-2007, 01:19 PM   #13
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The non bb T25 is used on 200sx's and many other vehicles but on the 200sx the elbow from the block that supplies the turbo oil line has a 1mm/.040in restrictor!!

Just to muddy the water.

I'm running with 1/16" restrictor.

Malcolm
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Old 06-01-2007, 01:25 PM   #14
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Hey brian,
I wasn't jumping to the conclusion.....It says it plain as day in braineack's faq that a .060 restrictor is probably required, but doesn't say anything about bb vs non bb turbos. I never knew that the bb turbos were the ones requiring restrictors, while the non bb's don't crucially require one. I didn't make my original post say 'here's what i'm doing...' i posted it asking for the experienced guy's advice. Which I have gotten...but you seem to be giving it with some what of an attitude that I don't think is necessary.
Thanks to everyone that has replied to this post. I now know that bb vs non bb changes restrictor requirements. And that a restrictor is not always necessary, but most guys use it to suit their personal application. Thanks for the help!!!

Anthony
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Old 06-01-2007, 03:06 PM   #15
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Yeah, well, Scott needs to ammend his FAQ, then. You can't just say across the board that most turbos require a .060 restrictor.
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Old 06-01-2007, 03:13 PM   #16
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ill say whatever i want ***** *****...


but what it says is this:
Quote:
Also determine whether or not your turbo will require a restrictor on the line as well. Some turbo have a built in restrictor and others tend to need a .060" restrictor fitting just before the turbo.
i probably could elaborate....
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Old 06-01-2007, 05:03 PM   #17
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Yeah, that's not as misleading as...I was lead to believe
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Old 06-01-2007, 11:35 PM   #18
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Yeah.....a little more elaboration in the faq would have been nice, but there is nooo worries.

My original question:
"Should I or should I not put an .060 restrictor in my supply line?"

Was never jumping to the conclusion that I definitely should....
I was asking if i should and....if i should, i proposed a solution to putting one in on the plumbing set up that i have.

I'm not sayin brainy's faq was misleading at all...was just wondering what i had to do for my specific application. Peace my friends! and thanks for your help!

A
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Old 06-02-2007, 10:39 AM   #19
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Yeah, I was saying Scott's FAQ was a little misleading, but it's really not...it's just a bit...sparse, with regard to oil restrictors. The reason is that there are so many different applications and turbos, that it's difficult to really say with assurance whether or not you'll need one.

You're not going to instantly kill a turbo with too much oil, though, so I'd just run restrictor-less initially and see if it smokes, behaves strangely. I would not be surprised, on the other hand, if you killed a turbo fairly quickly by starving it of oil.
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