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oil supply/pressure

Posted: Thu Jun 20, 2013 11:53 am
by acer
i have a question about oil supply/pressure for the turbo on a 86 trooper. everthing is stock as it came out
but ive had a turbo fail and was checking out all possibilities and have found that engine oil pressure at sending unit fitting is around 80
psi. checked oil pressure at end of line that supplies the turbo and its 20 psi. seemed low to me so i slowly pinched off supply line to vacuum pump
and pressure rose to around 60 psi. is this normal or am i ANAL about putting on a 500 dollar turbo and having it hogged out too. thanks

Re: oil supply/pressure

Posted: Thu Jul 25, 2013 8:48 am
by Tuggnutt66
well not being a Isuzu guru..and not having a manual in front of me I would say 80 seems high for main gallery pressure. The turbo and the vacume pump are going to be both getting oils supply from the same oil passage and therefore the vacume pump will be lowering the pressure at the turbo. It would probably not hurt to contact a turbo guy and see if 20 psi is enough for the turbo....also its not JUST pressure but VOLUME that may be the key.
Hope that helps.

Re: oil supply/pressure

Posted: Thu Jul 25, 2013 8:53 pm
by joeshmoe44883
80psi is normal with cold oil. turbo bearings need pressure to float to prevent bearing wear, this happens around 30-35 psi, but its only needed when the turbo is spooled up making boost. 20psi at idle should be plenty. if your paranoid about it, you could always tap directly into the oil gallery, on the passenger side, right above where the oil pan bolts on, should be some allen screws. these plug holes that go right to the gallery.