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Thread: ?? Do I need a oil restrictor??

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Posts: 1-10 of 12
2012-06-08 16:10:10
?? Do I need a oil restrictor??
Car put together by someone else before I bought it.........

W10 DET with GT2871R, hard lines modified to fit - Installing a SR20VE front cover - Wondering if I need a oil restrictor or not? I was advised by someone that one might be needed.

If so, do they make one to work with the hard lines? If not, where can I get the lines?

Figured I would come to the pro's here........
2012-06-08 16:31:46
I still don't think you need an additional restrictor. There is one built into that turbo, and those hard lines are the right size. You should be fine, even with the additional flow of the VE oil pump. The key is to make sure your oil drain is flowing as good as it can.

FYI I have a VE oil pump on a T28 and I'm not using a restrictor either, with -3AN lines (if I had -4AN lines like most people I would run a restrictor).
2012-06-08 18:14:02
does this apply to the disco gt2860rs? would i need a restrictor if i run -4AN lines?
2012-06-08 18:48:27
Journal bearing turbos need more oil, so they tend to have little to no restriction built into them. BB turbos all need less oil, so they have restrictors built in. What that means is, all turbos of similar frame size need similar amounts of oil flow regardless of bearing tech. Small frame turbos with stock lines or -3AN lines regardless of journal bearing or ball bearing should be okay with no additional restrictor as long as the oil drain is working properly. The oil drain is key here.

If you're running a small frame turbo with a -4AN feed line (why people do this is beyond me) then yes you'll likely want to run a restrictor. What size? I don't know off the top of my head.

If you have a medium frame turbo, the -4AN line is fine with no restrictor.

The reason for the restrictor is so that you don't overwhelm the oil drain. That is it. Once you overwhelm the drain, you'll have frothy oil blocking the drain which will cause a huge pressure gradient across the turbo bearing and you will blow oil through one seal or another. If you scavenge the oil drain or have some other extremely high flowing oil drain then you can feed the turbo as much oil as conceivably possible and it would be fine.
Last edited by BenFenner on 2012-06-08 at 18-51-48.
2012-06-08 18:57:25
Originally Posted by dorsey61
does this apply to the disco gt2860rs? would i need a restrictor if i run -4AN lines?

yes you need one. the restrictor built into the turbo is not small enough for a -4an line.
2012-06-08 19:00:39
-4 size Oil inlet fitting for GT28/30/35R with built-in restrictor : atpturbo.com

-3 size Oil inlet fitting for GT28/30/35R with built-in restrictor : atpturbo.com

Oil Inlet Restrictor - .065" hole size 1/8" NPT (for Journal bearing and larger GT BB) : atpturbo.com

2012-06-08 19:16:28
Thanks for the clear up.. ill run the -3AN line. Are there any rules for restriction with the coolant feed and drain??
2012-06-08 19:20:34
Coolant goes through a water jacket, and can be whatever size you want within reason. Just make it work.

The oil drain needs to be wide open, unrestricted, the fewer turns the better, and the angle of flow needs to be down as much as possible. It is a gravity drain situation. The oil is under no pressure when it drains and is frothy with air which makes the volume maybe 5-20x more than normal. -10AN line or similar size is common. Our stock oil drains are plenty adequate as well. Don't do anything silly.
2012-06-08 19:22:03
Originally Posted by dorsey61
Thanks for the clear up.. ill run the -3AN line. Are there any rules for restriction with the coolant feed and drain??

no issues with coolant lines. Only restriction on the oil return is that is positioned properly and line in not kinked. I usually use a 5/8 silicone hose for the oil return and 3/8 for the coolant lines.
2012-06-08 20:13:45
I run a restrictor on my turbo. After a couple years of daily driving the car I haven't seen any issues from it. Turbo spools like the day I bought it. I drive the car all over the place, including 1600 miles to this years convention. If you read the Garrett site, a restrictor is suggested for turbo spool mainly. If you are running more oil over the turbo than needed the turbo will not spool as quick. If you don't run a restrictor I don't think anything bad will happen besides a possible slightly slower spool.


Q. Does my turbo require an oil restrictor?
A. Oil requirements depend on the turbo's bearing system type. Garrett has two types of bearing systems; traditional journal bearing; and ball bearing. The journal bearing system in a turbo functions very similarly to the rod or crank bearings in an engine. These bearings require enough oil pressure to keep the components separated by a hydrodynamic film. If the oil pressure is too low, the metal components will come in contact causing premature wear and ultimately failure. If the oil pressure is too high, leakage may occur from the turbocharger seals. With that as background, an oil restrictor is generally not needed for a journal-bearing turbocharger except for those applications with oil-pressure-induced seal leakage. Remember to address all other potential causes of leakage first (e.g., inadequate/improper oil drain out of the turbocharger, excessive crankcase pressure, turbocharger past its useful service life, etc.) and use a restrictor as a last resort. Garrett distributors can tell you the recommended range of acceptable oil pressures for your particular turbo. Restrictor size will always depend on how much oil pressure your engine is generating-there is no single restrictor size suited for all engines. Ball-bearing turbochargers can benefit from the addition of an oil restrictor, as most engines deliver more pressure than a ball bearing turbo requires. The benefit is seen in improved boost response due to less windage of oil in the bearing. In addition, lower oil flow further reduces the risk of oil leakage compared to journal-bearing turbochargers. Oil pressure entering a ball-bearing turbocharger needs to be between 40 psi and 45 psi at the maximum engine operating speed. For many common passenger vehicle engines, this generally translates into a restrictor with a minimum of 0.040" diameter orifice upstream of the oil inlet on the turbocharger center section. Again, it is imperative that the restrictor be sized according to the oil pressure characteristics of the engine to which the turbo is attached. Always verify that the appropriate oil pressure is reaching the turbo. The use of an oil restrictor can (but not always) help ensure that you have the proper oil flow/pressure entering the turbocharger, as well as extract the maximum performance.

Last edited by gomba on 2012-06-08 at 20-31-44.
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