What size oil drain bung
Just want to get that taken care of while the engine is out.
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For the best possible gravity drain you should measure the drain ID on your turbo and not go any smaller than that IMO.
You get into problems with cheap china AN fittings. Here is a AN12 fitting. Using a 3/4" threaded T6 S400 drain. As you can see the ID of the fitting is no where near 3/4".
Here is a "push lock" AN12... same problem!
I use the threaded 3/4 T6 drain with copper tubing. Then solder them together. Never had one leak...yet. I use an unrestricted -4AN line as a feed on all my stuff.
Last edited by Forcefed86; Dec 10, 2014 at 01:35 PM.
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Jay
Also I hear ya on the china AN fittings. I believe the common JIC steel fittings are similar.
Jay
Jay
Not a good idea IMO for a journal bearing turbo. Especially if your just randomly picking a restricted orifice size. Personally I would never restrict a journal bearing turbo unless there were some odd over pressure/flow circumstance.
You should have "X" amount of flow per min through the turbo at idle and WOT. Unfortunately a lot of turbos these days don't have a proper service manual. If they did, you would see the required feed/drain sizes as well as the pressure requirements and flow requirements through the center section.
For example... this is straight out of a HX35 FSM.
...
11. Oil return pipes are permitted to decline at an overall angle of not less than 30 degrees below horizontal.
...
14. The minimum oil pressure when the engine is on load must be 210 kPa (30 lbf/in2). Maximum permissible operating pressure is 500 kPa (72 lbf/in2) although 600 kPa (88 lbf/in2) is permitted during cold start up. Under idling conditions pressure should not fall below 70 kPa (10 lbf/in2).
15. Recommended oil flows for the turbochargers are 2 litre/min at idle and 3 litre/min above maximum torque speed.
Installation Data
1. Mount the turbocharger on the turbine inlet flange. All other connections must be flexible and heavy pipework
should be supported. Always pre-lube with clean engine oil.
2. Always position the bearing housing so that the oil drain is at the bottom and kept within 22° of the vertical centre
line when installed on the engine.
3. Oil should be filtered below 15/20 microns. The oil quality must be as specified by the engine manufacturer.
e.g. API - CD (MIL - L - 2104C). Improvement in life can be obtained by using super high performance diesel
(SPHD) oils, particularly where extended oil drain periods are used.
4. Oil pressure must show at the turbocharger oil inlet within 3 - 4 seconds of engine firing to prevent damage to
turbocharger bearing system from lack of lubrication.
5. The minimum oil pressure, when the engine is on load must be 210 kPa [2.0 kgf/cm2, 30 lbf/in2] and pressures up
to 415 kPa [4.0 kgf/cm2, 60 lb/in2] are satisfactory. Under idling conditions the pressure should not fall below 70 kPa
[0.7 kgf/cm2. 10lbf/in2].
6. The oil inlet pipe should be 9.5 mm [0.375 in.] bore minimum and the oil drain pipe should be 19 mm [0.75 in.] bore
minimum. The oil must drain downwards by gravity from the turbocharger into the engine under all operating
conditions.
Last edited by Forcefed86; Dec 10, 2014 at 03:09 PM.
Jay
Last edited by oscs; Dec 10, 2014 at 02:42 PM.
Bottom line is force fed is right. I would match your drain line ID with the orifice size of your drain if space allows.
In the import world it’s very popular to use the Holset turbos. Members ran into smoking problems trying to use the factory 1/2” (or smaller) drain lines with Holsets. Restricting the feed was the answer for years. Many damaged turbos later someone eventually dug out a Holset manual. We were all very surprised by the minimum flow and drain requirements . One of the popular turbo re-builders in the DSM world claimed he “lost all his business” once the correct supply and drain lines were used
Last edited by Forcefed86; Dec 11, 2014 at 09:26 AM.
Last edited by oscs; Dec 10, 2014 at 11:30 PM.





