A previous post "Search" gave conflicting info:

I want to set oil pressure to turbo by adding a pre-turbo restrictor to the oil feed from the pump oil pressure gauge tap/top end oil passage. I have a needle valve oil restrictor and want to set oil pressure into turbo AFTER restrictor. (typical restrictors use @.065 orifice)

The Inline six build runs @ 60-80 (or more) cold and then @ 40-60 warm at the pump tap.

TBO-3 Air Research - 70/s carb'd buick v6 OEM application

thanks

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What is the question?

 

Simply , What oil pressure at turbo inlet is recommended or can be measured as typical (min./max ?) . Are oil line restrictors a good idea? (typical reducer restrictors use @.065 orifice) .

...my current turbo project, on initial engine running the turbo oil return visibly looks like a lot more oil is delivered through turbo when revved and engine oil pressure rises .

The Inline six build runs @ 60-80 (or more) cold and then @ 40-60 warm at the cam rail gauge tap and has another oil pressure gauge at turbo oil inlet, I have a needle valve oil restrictor that could set oil pressure into turbo or simply add the pre-turbo oil restrictor-orifice to the oil feed .

TBO-3 (T3) Air Research - 70/s carb'd buick v6 OEM application

info appreciated
thanks

 

Different manufactures will have different ratings for their center design and bearing design. In general 40-50psi is more than enough for journal bearing and 20-30psi is fine for ball bearing. In general no smaller than .065 for journal if pressure exceeds that rating and no smaller than .035-.040 for ball bearing if it exceeds that rating. 3an feed 8-10an drain for ball bearing. 4an feed 10-12an drain for journal.

 

Just keep in mind that when you restrict oil, you're not directly lowering the oil pressure, but you're limiting volume which in turn drops oil pressure after the restrictor as its starving the turbo for oil. This is fine for a ball bearing turbo, but very bad for a journal bearing. In my opinion a restrictor should be a last resort in oil control, and needing one is a sign of issues elsewhere. Many oem turbos have -8 feeds, and oil pressures nearing 100 psi without issue.

 

In my opinion a restrictor should be a last resort

Thanks for the discussion, i'm a newbie here and to turbo's in general.

... I'm not clear if any maximum engine oil pressure is bad for my turbo ever, and needs an amount of restriction?.

... aLso setup uses engine oil pressure sensor tap for 3/16" turbo oil feed from end of cam at the passage to cyl head - could tee be bleeding off too much volume/pressure from the engine's own oiling ? . (Eng. oil press. is normal)

have fun

 

Excessive oil pressure (within reason) isn't bad, but it will cause the turbo to pass more oil, and can cause drain, and smoke problems... which is the reason most limit oil in the first place. As long as your engines oil pump is up to the task of supplying oil to two additional bearings (turbo) and maintaining enough pressure all will be fine.

 

... I'm not clear if any maximum engine oil pressure is bad for my turbo ever, and needs an amount of restriction?.

... finally found and read this post :

https://www.theturboforums.com/thre...ze-for-journel-bearing-90-PSI-of-oil-pressure

... it's a draw , unless turbo mfg specifically specs it, consensus is it's not needed to protect the turbo itself...

Typical restrictors when advocated are @ .060 - 1/16", the popular option and if used can help smoky turbo's sometimes.

I think missing in the 1/16 - .060" restrictor discussion was how typical engine oil weights perform cold vs hot. - the oil volume when cold and higher pressure through the flow restrictor vs warm thinned oil volume at temp'. The @1/16 - .060 restrictor may provide a simple temperature/pressure adjustment - when advocated.

>Maybe using 1/16" oil feed line (typical gauge) , (AN ?) to the turbo could provide simple temp/pressure control option, the amount of returned oil at full temp and revved RPM pressure was my initial concern.

have fun

 

I totally agree... the pressure is being lowered by restricting the volume with a fixed orifice, and will have different results with different oils at different temps, and at varying input pressures. Restrictors have a place, but shouldn't be the first option, and should be taylored to each engine/turbo combo if needed. Proper setup would require monitoring post restrictor pressure, and or drain volume imo.

 

Excessive oil pressure (within reason) won't damage the turbo (unless causing drain issues for an extended period of time), but will cause it to pass more oil, and possibly cause the return oil to back up into the turbo which causes smoke, and seal leakage. Personally I run -4 feeds, the largest, straightest return I can, keep the crankcase well vented, and if there are still issues, then deal with limiting oil. Just my 2 cents.