Oil Inlet Restictors... research and opinions
 

It must have been doing this from the start, only the cat was burning it all up. Now that the cat is gone, it's smoking ever so slightly and I've got oil residue at the exhaust tips. I didn't check the IC pipes... a little afraid to. However, based on my research, I've bought into the oil inlet restrictor thing and am getting one.

First, my research. Here's a few posts that got me started:
https://www.miataturbo.net/forums/sh...ght=restrictor
https://www.miataturbo.net/forums/sh...ght=restrictor
https://www.miataturbo.net/forums/sh...ght=restrictor
Then I just google'd the shit out of everything I could think of... mostly looked at posts in other import forums.

These next statements are generalized.
Your average Ball Bearing turbo doesn't need as much oil as a Journal Bearing (non-BB) turbo. Most guys with BB turbos (do or should) run a .035 restrictor and -3an line. Most guys with JB turbos (do or should) run a .060 restrictor and a -4an line. Of course this all depends on how much oil pressure your particular car makes. Jap cars don't seem to vary that much in the amount of oil pressure they can provide... say about 20psi at idle all the way up to 100psi maybe at WOT. I took a drive today and at WOT I saw as much as 80psi. At that pressure, an unrestricted -4an line should ensure that my entire intake and exhaust system has a good coat of Mobil 1. Not to mention severely limiting the life of the seals in the turbo.

It seems to be a given on other forums that a restrictor be an automatically included piece in any turbo system. No kidding, DSM, Honda, Subie, SR20, etc... all the posts I read just take it as a matter of course that you run one. They say even if you're not leaking now, you will be. Some guys get away with it of course, but it looks like I'm not one of them. So... I'm in!

QUESTION: Should this be something we as a forum start to mention to NEWBs that they invest in (like motor mounts that nobody ever thought of until a few weeks ago). Brain points it out in his FAQ, but I never hear anyone talk about it unless someone brings up that they're smokin'.

Anyways, I'm pretty sure that the ATP restrictor for the GT series turbos are also 1/4 inverted flare, but it comes with a .035 restrictor... just need to drill it out to .060 (where the hell do I get that bit?.. a 1/16" is .065... guess that will work). Here's the restrictor: http://www.atpturbo.com/Merchant2/me...gory_Code=GTBB

Anybody know where I can get a .060 1/4"IF to 4an for a T25???

I dunno much about restrictors. However, just so it is written to not spread misinformation I know for a fact that ALL GT series BALL BEARING turbos have an oil restrictor built into them. The restrictor that ATP sells is most likely for the GT series with a standard journal.

On another note, you might want to just go ahead and shoot an email to ATP tonight so you can get a reply sometime tomorrow. They should be able to answer you incase no one here can.

wouldnt a restrictor also help with oil pressure?

That restrictor is for GT Ball Bearing Turbos. R=Ball Bearing.

www.jgsturbo.com has the restrictor you need.

I use one in my JB turbo, and blew the seals immediately in my first turbo because of the lack of an oil restrictor. I'm not real saavy on the BB stuff, but for a JB I wouldn't even attempt it without one.
-Michael-

I think it really depends on the turbo; I'd take it on a case-by-case basis. I, too, have heard that many of the GT BB turbos are self-restricted, but I wouldn't trust that every one will be this way.

When I built my turbo kit, I checked the Volvo 940 that it came off of, and saw basically a 1/4" feed line with no restrictors, so that's how I feed it on my car. I've been running it over a year, and it's never even hinted at producing smoke.

while my T3 JB would smoke at idle without a restrictor.

Would seem that a restrictor that we could add between the 4AN line and whatever 4AN fitting we have in the turbo (or better, at the block) would be the simplest solution, instead of dealing with all the fittings to adapters to restrictor to adapter to line issue.

Anybody find a source for something like that? I haven't been able to.

Yup, about halfway down this page: http://www.jgsturbo.com/index2.html
It says that a T25 is 7/16", but I know the 2G DSM CHRA I'm using is 1/4"... WTF with these things... WHY CAN'T THEY ALL BE THE SAME??? Wouldn't it be easier to just make the threads on all turbos universal. SHIT!

I thought that GT turbo's were all BB's... that's what makes them "G".

You'll still get that same pressure of oil at the restrictor, but it will let less oil through. I think the idea is not to let the CHRA fill up with oil and become pressurized... A bigger drain is not an option, so less oil in is the key.

mine is a Male/Female that screws right into the turbo, my regular 90* fitting then screws into it.

http://www.rev2red.com/images/cars/turborebuild002.jpg

Sam I'd suggest using the one you linked to in your first post and drilling it out a bit. Nothing wrong with that. Some people go crazy lengths do make them: http://www.dsmtuners.com/forums/showthread.php?t=171317 The one you found would take 3secs to drill out.

What makes them GT's are the new compressor and turbine wheels that an improvement over the standard T stuff. What makes a GT a "GTxxR" is the ball bearing center section.

I'd be all over that if my 1g dsm turbo with it's stupied 12 x 1.5mm oil feed port!

It's still a -4an fitting though? You could do a -4AN M to FM fitting for like $3 and try the NOS nozzle trick.

Sam, something you could do for now is run a 1/8" aluminum poprivet inbetween your two AN fittings at the turbo for now. The inner diameter of the rivet is .075" here's a post on my oil pressure measurements on my 99 1.8 with -4 AN line.
https://www.miataturbo.net/forums/sh...5&postcount=14

I think there was a thread on M.net the other day where folks were/are using pop rivets. They apparently fit right into the -AN fitting, and there's a couple sizes that work.

Here it is: http://forum.miata.net/vb/showthread.php?t=209249

Edit: Whoops, there I go again waiting too long to compose my post :)

h**p://forum.miata.net/vb/showthread.php?p=2178338#post2178338

The thread I had posted in about using pop rivets, looks like he had great results. Can't hurt they're $1.25 for a box of 20.

That aluminum rivet thing is the deal. I'll stop by Home Depot on the way home and see what they have. As a side note, it started smoking pretty good today. I hope I haven't done any serious damage. Looks like I'll have to check the charge pipes after all when I get home today.

I'll let y'all know what I find out.

Speaking from experience, contaminants can also enter the turbo via the oil feed and block some of the oil passages. In my case, some permatex rubber somehow got in there from the previous owner thus starving my turbo of oil. Even if you were careful in the rebuild, something could have gotten in there. If the restrictor doesn't help and you're positive the drain is flowing the way it should then you might want to check the shaft play on the turbo again to see if you're having oil starvation problems which could be evident in journal bearing wear.
This has happened to me twice.

OK, here's what I got. I bought some 1/8 short aluminum rivets, popped the nail out, and put it in there.

You can see the oil inlet is no smaller than the 4an line or the brass fitting.
When I tested the rivet on a spare oil line and fitting, it flattened out considerable when I put the wrench on it (guess that's why you use aluminum). I only got to drive it for about 15 minutes and it smoked a little in the beginning once it got hot (probably burning off residual)... so hopefully that does it.

On the other hand, I decided for my "leak" test drive to hook the turbo back up... and my wastegate flapper was stuck open (caught on something- think the Begi gas separator flange- inside the DP). I unbolted the DP and moved the flapper door back to reconnect the wastegate and broke a bolt off in the turbine housing. So, now I'm running on four bolts. No audible leaking, but something to fix next time I've got the turbo off... which might be sooner than later, because on my drive, the flapper door got stuck open and I had to drive a few miles home w/no boost. POOP!

You'll notice in my vbGarage that previously I'd routed the oil line across the firewall and through the brake hard-lines and into the inlet via a 90* brass fitting. For ease and simplicity of using the rivet, I left out the 90* fitting and now just go straight up the dipstick and over the top straight down on the inlet.

I had a slightly different solution for the restrictor that I used in my setup. I found a bolt that was just slightly larger than the inside diameter of one of the oil fittings. I tapped the fitting out so that I could thread the bolt in. Then I drilled a 1/16 hole in the bolt, threaded it in tight and cut off the extra that was sticking out. Seems to work well.

If I had seen the rivet method though, I probably would have done that instead.... I suppose that you could also put JB weld into a fitting and then drill that out.

Nice pictures of the rivet method. Starsky's bolt method is easy enough and would give you the ability to use whatever hole size you wanted but not as simple as just putting in a rivet. I would never put JB Weld in a fitting and drill it out, the oil pressure is high enough that I wouldn't trust anything like that in my oil system. Let alone before the turbo where it could possible break apart and get inside the bearing housing. Nice pictures Sam hope that broken bolt comes out easy enough for you. Interested in seeing if the rivet stops your smoking or not.

Interesting with the rivet. I use an FM oil line kit, its a -3 and they told me no restrictor was needed. I use one anyway, the same .035 restrictor from ATP, I drilled it out to something, but just used a bit I had lying around, so its not that small. 1mm maybe. No problems yet.

would it be fine to put the restrictor down closer to my block????

Does a Greddy Turbo standard kit need a restrictor ?
I've had my Greddy installed for....gawd...over 2 years or so with no oil burning/smoke problems.

You wouldn't want to. It would restrict flow to the feed line, thus the line would feed slower than normal leaving your turbo without oil(possibly) upon startup. You need to do it at the turbo.


Most -3AN feed lines don't need require a restrictor.

The stock greddy shouldn't need one. I wouldn't use a restrictor on a turbo unless it smoked.

ok so how can i install the poprivet restrictor if i have a banjo fitting at the turbo? would it be fine to drop it in with the bolt?????

You shouldn't use a restrictor on the Greddy kit. The turbo is oil cooled/lubricated. The oil is the primary coolant of the CHRA and require significantly more oil than an Oil/Water turbo.
I'm not sure how you'd do it with a banjo bolt. There shouldn't be any problem using the restrictor at the block though. Also, it's just as easy to spend $10 for the parts to get a 90* fitting instead of the banjo.

ok so what should i do then??? my greddy has been rebuilt twice and has lasted about a month has verry little shaft play and has oil in the exhaust now.....

How are your PCV ports routed?

https://www.miataturbo.net/forums/at...4&d=1165887655

This is very similar to what I use, but I use Nitrous jets. They come in all sorts of sizes, I used a .032 I think on my GT28R.

I use nothing on my journal bearing turbos, been lucky with no problems.

I've always used 4AN lines cause they are easier to find fittings for.

pcv is routed norm and i have the 1.6turbo one in there from the capri/323 turbo