I'm replacing my Master Power T70 with a Turbonetics T70 in my RX7. It should be a straight swap, but I got ahold of Turbonetics just to see what they recommend for an oil restrictor (if any). With the MPT70 I bought it used and it came with one so I just used that, but I think it was just an NPT-4AN fitting with no restrictor inside.

The considerations are:
T70 is journal bearing
Engine runs ~80PSI oil pressure warm
-4 feed
-10 drain, no kinks or weird angles

Turbonetics recommended Vibrant's restrictor since it comes with a few different sizes. When I told Turbonetics the specifics of my setup and asked what size they recommend, they simply replied "-3". I take it to mean if I have a -3 feed I will be in the clear and not need an actual restrictor? In that case, what would be an equivalent restrictor size to put in my -4 line? I don't have any -3 line around and I don't want to replace my feed line since it would require me to remove my intake manifold.

 

The dash system is 1/16's, so 4 is 1/4", and 3 would be 3/16". So basically 1/16 smaller than whatever your -4 measures.

 

Thanks, you learn something new every day! So basically I just need to find or make a 3/16" (0.1875") restrictor. Everything I see is significantly smaller so I'll just drill my own.

 

The hose is theoretically 3/16, but any hose barb, or crimped on end will be smaller and the point of restriction.

 

True. I'll ask around and see if I know someone with a -3 fitting I can check out.

 

I'm just guessing here, but I bet .125" will be close.

 

Why are you using restrictors? This will only limit the oil supply to your turbo bearings. Is there a problem of a leak or smoking? IMO I'd increase the size of your return line and try to fix the problem after the turbo not before it. Your -4 feed and -10 return should be more than enough. I would only use a restrictor as a last resort after you've tried everything else.

 

I feed my t-70's with -3 lines.

 

I've always said the same thing.... but with 80 psi warm, a -3 really isn't a restrictor. Its the guys running .040-.060" restrictors with journal bearings, and 40 psi hot rather than addressing the real issue that are asking for trouble imo.

 

I am using a restrictor because the manufacturer told me to use a -3 line and I have -4, so I am just getting it down to -3 size. For reference, my Master Power T70 was running restrictor-less on the -4 feed, but eventually ended up leaking out between the CHRA and hotside, and also smoking. It did last a couple years (though very few miles, the car had a lot going on in there) before it did that though so it may have been unrelated.

I could up the drain size to a -12, the -10 was just very convenient because of the commonly available -10 drain flanges that bolt directly to the factory turbo drain on the engine.

 

The larger the drain the better. -10 is what most consider a minimum, but other things factor in as well, and the larger drain can only help. I wouldn't worry at all about the -3 size if you have that kind of pressure while in boost.

 

I wouldn't use any restrictors, because restrictors limit the amount of oil that lubricates and cools the turbocharger. If you're having issues with a smoking turbo, get a bigger drain.

 

Some mfrs put restrictors on ball bearing turbos only.

Al

 

IMO, solve the high oil pressure problem. I've had leaking issues twice with fresh turbos and after researching this issue about the only people that have leaks are the ones that have high (over 60psi) oil pressure. So I'm going to fix this issue by installing a pressure relief valve and bypass the oil back to the pan with anything above 60psi and I'm removing the restrictors completely now that I can regulate the oil pressure.
I am also installing a scavenge pump to suck the oil out of the lines and back into the pan.
The -4 lines feed the two turbos and the -8 is the bypass return line.

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A restrictor should be the last resort, but if sized correctly works well. Too many guess at a size with no info to back it up.... Place the restrictor just upstream of the turbo and plumb a pressure gauge between it and the turbo. As long as you have 35+ psi while in boost the turbo is getting all the oil it needs.

 

If a turbo comes with a restrictor (which most ball bearing turbos do) I would not remove it.

Al

 

All the journal turbos I've seen have a built in restrictor in the cartridge. Running a -3 or a -8 hose to the turbo feed won't matter. Unless you restrict the passage more than the built in orifice feeding the bearing. I can't see it doing anything.

That's talking journal bearing only.

 

Here's a Garrett t3/t4 center. It has a .250 opening to the bearing which is the same as a -6 hose end. I wouldn't doubt some import turbos have a built in restrictor. #ad
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Does that go straight through? I haven’t worked on any dinosaur turbos… but most made this century will have a built in restriction of some sort to distribute and control flow.

Like these

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It intersects a channel of the same size. I have some bare centers at home, I'll take look and measure them. It is a dinosaur, but many (China and others) are still copying it...