Oil Restrictors for DBB(35R, 40R, 42R), What Garrett says...
 

Well I spent the weekend at JGTC, and had a chance to talk to severalGarrett Reps about their GT turbos, and specifically restrictors. Here is what Brian Reigner of Garrett, and two other reps at the booth said, (it is noteworthy that I had a friend ask a different rep the same question seperately, and got the same response)
1- are the GT turbos internally restricted? answer; YES
2- Do DBB GTR turbos require an oil restrictor? answer; if the oil pressure at the inlet is over 40psi, then YES.
3- how do you recomend restricting the pressure? answer; You can use the .035 restrictor from ATP or make your own, so long as pressure at idle does not fall below 15psi at the inlet.
4- what is the recomended range in psi for the GT turbos while boosting? answer; 30-40 psi, NO MORE, or you will get oil blowing by the piston ring (for lack of a better term) seal, and YOU WILL LIKELY HAVE PREMATURE FAILURE OF THE CHRA.
5- So, if users have oil blow by, could that be considered normal, or is that ALWAY indicative of a problem? answer; IT is a problem, and must be addressed for max life of the CHRA.
6- If a CHRA fails, do you have to replace the entire cartridge? answer; Yes, but Garrett is working on an exchange/rebuild program for the BB turbos, that should be available in the near future.


So, whatever you do, I would recomend that you determine the correct restrictor for your particular application, by measuring pressure after whatever restrictor you are running. You will need to do this through the entire operating range of your motor to be sure that the oil pressure stays within these parameters, and if you blow up your turbo, you've got a name at Garrett to help you through. I let the Garrett guys know that I would post this, and they were entirely comfortable with the posting of the info.

I know that several prominent vendors have stated that an additional restrictor is a bad idea. I think that in hindsight, that is an over simplification that can cost you alot of money. I feel that actual testing is the only way to determine the correct restrictor for your car. Remember, the ATP restrictor is made with Audis, and VWs in mind, I do not know the oil flow characteristics of those cars, but I would start big, and work my way down in terms of restrictors.

See my next thread on T4 35R housings. Happy holidays, Carl

Excellent information :bigthumb: especially the maximum pressure ratio information.

Excellent information. Thanks for taking the time to ask and post it up here. When you have a turbo that cost $1,500 and up, you want to make sure you are running it under optimal conditions. This certainly concerns me with some of the earlier post I've seen on the forum and even some of the venders who sell these turbos who don't have or give this information out.

What is most troubling is that by each vendors account, the info they share came from Garrett. Since so many are having problems, I think this is a good starting point. wish I had taken photos of the cut away 40R, so I could show you the internal restrictor, and where the oil is passing in the bearing assembly...

I have yet to have any problems with any turbos installed here at the shop, no restrictor some going on over three years, ran hard. When I spoke with them I was told it was a not a good idea. When I spoke to others very recently (2 weeks ago), I was told you can restrict it and restrictor size should not allow less than 12psi@ idle and no more than 35psi max. When I asked would the internal restriction make up the difference it was "only to a point and if pressure was excessive it should recieve additional restriction inline and to start with a .040 and go from there, and that it should be measured throughout engine operating range."
With that said how critical is it? I'm not sure as I've said I have dozens of these things running no issues, no failures. So I would say some restriction might not hurt but I would worry more about too small more than too big.

what is the oil pressure of the stock oil pump and regulator on fc's?

I was told 12 psi(min) too, I padded it to 15psi to allow for different gauges. I promise that is the only number I did that with. The 40psi was the number at which blowby was likely per Garrett. At least we now have a range to work with. I certainly concur as to testing operating range, and starting big, as suggested above. The main thing that concerned me was the statement that if you had enough oil pressure to blow by the seal, that the seal was being damaged/compromised, and would likely cause a failure.

I get a different answer every time I talk to someone different. So I just take it as opinon almost. I was told the turbo will smoke slightly for awhile due to the seal endgap but once that becomes built up with gunk it will stop. This is almost always what we see, no restriction. It wouldn't hurt to restrict it some, I just wouldn't go smaller than .040.

We had a GT40R at a dyno session here that was smoking REAL bad. We redid the crank case (oil pan) vent and the smoking totally stopped on the next run. If the oil cant drain fast enough its going to build pressure in the chra and oil inlet.

I would suggest anyone with these problems to look at thier crank case vent before doing anything drastic like oil restrictors. Its very simply to run all the crank case vent to atmosphere or to the intake. One take 5 minutes.

I've got a race oil reg from mazdatrix, who informed me it was better to run high oil pressure than stock. Since this makes no sense to me, someone please point me in the right direction. I have a GT40 turbo. Running 115psi of oil pressure seems awfully high, but I wonder what it would be at the turbo inlet. I suppose I could always measure it?

I belive that kind of oil pressure is fine for the motor.But not the turbo that is way to much.

Also, keep in mind that the oil pressure on a gauge could be totally different from what it is at the turbo. The oil pressure can change in different parts of the system, I've never measured it but the oil pressure going into the turbo is probably significantly lower than what you see on your pressure gauge. Someone should try setting up a gauge just before the turbo's oil inlet and see what they get.

Either way, the pressure can be lowered by helping the oil to move faster. I've found crank case pressure to be a problem with dynamic and bb turbos (not just Garrett) and they were all fixed by venting all of the crank case nipples to atmosphere or the intake. If this works you should probably put a catch can on the lines.

Carl your a F8cking legend mate ;)

I asked a local turbo retailer here who supplied me my turbo's and liek the majority of monkeys in the industry in Australia they could not give specific numbers to answer very simple questions.

Glad you got it direct from the horses mouth !

I will mount a gauge direct via short bleed near entry of my twins and make sure of min and max pressure levels as per factory Garrett specs. My engien runs 120- 130psi oil pressure so very likley that it will be too high even after amking journey along the line tot he CHRA :)

Great stuff ;)

I am not sure I would call an inline restrictor "drastic" Stephen, any possible downsides to your fix? Sean, have you ever measured the pressure at the inlet? FWIW, the internal restrictor on the turbo is a simple ~1/10th" hole in an insert that sits inside the oil inlet before the oil reaches the bearings. Carl

According to the actual drawings It says.

"Minimum 31psi at peak torque speed and above and no lower than 10 psi at low idle. Oil outlet should be +/-35* when installed in vehicle on level ground . Recommended minimum id of oil drain tube is .50"

This is the same thing I posted numerous times.

Actual oil inlet size is .071" +/- per Drawings also.

Now when you look at the actual part and take measurements here is what you'll find.
The restrictor, on the ID measures @1.024"- this is measuring on the
internal threads, inside those threads there is a small hole in the side of
the restrictor feeding the turbo with oil. This side hole measures .032".
Then after the restrictor in the bearing housing going to the bearing
journal areas there are 2 holes that measure .076".
The threaded insert deadheads at the bottom and squirts out the small side
hole into the bearing housing, then feeds to the journal areas through the
two larger holes.

Again with all this said, I have yet to have any problems running no restrictor. The actual drawings give no maximum only 31psi minimum peak torque and 10psi at low idle. It also shows that internally it is restricted to .032

This is a good thread. What size oil feed lines are most of yall running? If you run a properly sized feed line you should not need additional restrictors.

-4 is what I was planning. Unless I can find something simple to make it into a -3. I can't find a fitting for the banjo bolt oil feed that exits as a -3.

parker does not make any -3AN hoses or fittings

a Aeroquip hydro shop
can fab any style -3AN hose you want
but be prepared for the price
cuase the -3AN swivel fittings are expensive
$30+ each

I consider restrictors pretty drastic unless you have a pressure gauge hooked up at the feed inlet and you know exactly how the restrictors are effecting things. If you dont then your playing Russian Roulette with your turbos. I've known of many people that thrashed a good turbo by restricting the hell out of the oil lines to get rid of smoking. They kept going smaller and smaller untill thier smoke went away because they were using that as a "gauge" that they were supplying the correct amount of oil. Not to make Howard an example but it just happened to him https://www.rx7club.com/single-turbo-rx-7s-23/size-matters-turbo-oil-restrictor-sizing-377032/ Most people that I've seen this happen to just had excess crank case pressure from blow by and thats what was causing it to smoke.

It may be about two weeks from now, but I'll see what I can do to measure the pressure at the turbo inlet.

It should be as simple as putting a tee at the inlet hose and connect the oil pressure gauge to the tee.

I can pick up a mechanical oil pressure gauge for the test. It's a Sun, but should get us close?

For the FD, from FSM, oil pressure relief settings are:

156 psi at the oil pump outlet
110 psi at the oil fliter inlet (after the cooler(s)).

FSM imples oil pressure gauge is after the filter, but I see over 100 psi when oil is cool.

Measurements at the turbo will be interesting.

If the restricter is already in the housing, how can you measure the oil pressure behind it?

:withstupi

actually, I take my stupid thingy back. The specs are for the oil pressure at the inlet, not at the bearings. Garret has already conluded that 40 psi max is what is needed at the inlet so as that their internal restrictor will function propperly. All we have to do is make sure we get the correct oil pressure values at the inlet. This can be done with a gauge placed at the inlet and an extra restrictor just before the gauge.

I would like to mention that even with all the problems I am having. With an empty catch can and clear vent lines(propperly functioning crankcase setup), I have no smoke. People who are smoking while boosting in a straight line or on a dyno should look hard at their drain and vent size/setup. Mine only smokes if my vents get clogged and I build case pressure which will stop up the drain. That being said, it has been noted that excessive oil pressure at the bearings can damage the chra as well as too little oil. We should be very careful here.

Mike

Why would you install an extra restrictor before the gauge for the intial test? Don't we want to see what the pressure is without it first? Then go from there.