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Turbo Oil Pressure/Temperature/Drainage/Feed Discussion 
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Joined: Tue Jan 15, 2008 2:31 pm
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I managed to end up on the right track with this early in my turbo career, however many do not. I'm plonking this thread here as something for those poor souls to trip over and learn from if they happen to pass this way.

1) Journal bearing turbos should NOT have a restrictor in their feeds. Some "internet wisdom" says otherwise, but that's based on worn out turbos with bad seals and/or bad drainage causing drama. Even with a high pressure against a non-stuffed journal bearing turbo, the Volume of oil passing through is self regulating via bearing clearances.

2) Good drainage is essential, the right size, the right end point, and the right angles downward (as steep as possible). In some custom turbo installations, this is done completely wrongly, and then a restrictor is added, if it was not already. Result: Decreased turbo bearing life from insufficient lubrication.

Last night the amazing Mr Piimae linked this document: ... _40_GW.pdf from which I'll repeat some items below.

Quoting the above:

Holset Service Manual wrote:
8. Normal oil temperature is 95+/-5°C (203+/-9°F). It should not exceed 120°C (248°F) under any operating condition.

11. Oil return pipes are permitted to decline at an overall angle of not less than 30 degrees below horizontal.
All turbocharger applications require a pipe of internal diameter greater than 19 mm which has integrated
connectors. To ensure oil drains into the engine under all operating conditions, the return connection
into the engine sump must not be submerged and the outlet flange of the turbocharger must be 50 mm
above the maximum oil level of the engine sump pan.

13. Oil pressure of 150 kPa (20 lbf/in2) must show at the turbocharger oil inlet within 3 - 4 seconds of engine
firing to prevent damage to turbocharger bearing system. A flexible supply pipe is recommended.

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).

19mm ID drain for a big Holset isn't unreasonable, however according to via's research last night, no one sells anything remotely like that.

I stumbled upon the Garrett FAQ here:

Quoting from that:

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.

Moving along, I never had temperature or pressure gauges on my truck when I was thrashing my poor Holset to within an inch of its life. It's lived past two engines, though, and into a third, so it's doing OK so far :-D Can someone such as m2cupcar comment on the above 90-100C standard oil temperature range, and 120C max with respect to what they've seen in service on their vehicles? I believe my truck needs a serious oil cooler on it, but I've not proved it, yet.

On the pressure side, I have some data from my bone stock non-turbo B230F engine running 6000km old Penrite HPR10 10w50 group III highly refined mineral oil (synth on the bottle, but...) The data I gathered was as follows: ... 6678509570 "Cold idle, in neutral. 55psi of happy #Volvo 240 #wagon #B230F oil pressure! :-D" ... 7530044416 "Hot idle, in neutral. 50psi of happy #Volvo 240 #wagon #B230F oil pressure! 47psi in gear, 75-80 @ shift, 88 limiter"

And the photos to match:



All input welcome! :-)


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Sat Jul 23, 2016 4:41 am
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