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    M50b29 oil pressure a bit strange?

    Recently built an m50 stroker, s50 crank, nonvanos 135mm rods, m54b30 pistons with new rings gapped over for turbo, new crank bearings, new rod bearing, Athena cutring headgasket, I use an m52 oil pump, use a vanos oil filter housing (used the vanos feed to feed the turbo), rebuilt hx40 with 3/4” oil return and 4AN oil feed w no restricter. The oil return is at the correct angle, and it is above the oil pan. All parts were cleaned and inspected prior to assembly.

    My issue right now is my oil pressure. When the engine is at cold idle the gauge would read 40-45psi. When the engine warms up and reaching operating temp, the gauge is reading 60-65psi. Isn’t it suppose to be the other way around? I am using 20w-50, is this oil not appropriate for this application?

    Yesterday, I decided to take the car around my block. I didn’t push the engine, no hard acceleration. When I got back into my garage, smoke was coming my turbine; there was oil coming out on the bottom of where the bearing housing and the turbine meets. Seal blown from too much oil pressure? Has anyone experienced this? Obstruction in my oil passages somewhere? I am getting oil pressure but it is just high at operating room temp and low at cold.

    thanks.

    #2
    Originally posted by mini612 View Post
    The oil return is at the correct angle.
    Vertically off the turbo you mean?

    How is your crank case vented?

    Originally posted by priapism
    My girl don't know shit, but she bakes a mean cupcake.
    Originally posted by shameson
    Usually it's best not to know how much money you have into your e30

    Comment


      #3
      Originally posted by Northern View Post

      Vertically off the turbo you mean?

      How is your crank case vented?
      I thought of this last night as I was eliminating what could cause this! Realized I have a closed catch can with no vent! Not good! I am going to try another catch can. Feeling so dumb and was focused on other things except this! Will update when I can. Thanks!!!
      Last edited by mini612; 06-20-2021, 03:39 PM.

      Comment


        #4
        Something is definitely not right. I took off the crank case vent tube and vented to atmosphere and made sure my intake pipings are all leak free. Started the engine, the pressure gauge went straight to 45 psi. Then as the engine warms up, I can see the gauge climbing up to 65 when the engine is at operating temp. No engine over heating according to 3 different gauges, oem cluster temp gauge, tunerstudio temp gauge, and a temp gauge I installed w a sensor at the lower radiator hose (coolant entry). What else could it be? Could it be the oil housing I used, that spring valve that allows oil to flow?

        Any leads will be appreciated, thanks

        Comment


          #5
          What's your oil pressure gauge/sensor setup (and is it logging through TS or is it just for a gauge)? Any chance it's not reading right - wrong sensor calibration in TS, counterfeit/knockoff sensor, etc?

          Your pressures may be a little higher just from running a heavier oil, but I don't think there's any issue with 20W50 unless temps drop below something like -10C

          Are those pressure readings both at idle? The cold start psi seems a little low, but some other threads have people saying cold start is that RPM as well.
          I don't think it would be the oil pressure relief in the block, it can't really make oil pressure go higher at idle.

          If the gauge isn't wrong, I think it could be the filter (clogged? wrong filter?) or a restriction/blockage in an oil passage somewhere because I don't see how it could make 65psi at warm idle without something restricting flow.


          For the turbine housing oil leak, it shouldn't matter what the oil pressure is as long as the drain is way bigger than the feed.
          No way should it be able to feed more into the turbo than a -12 drain line can remove.
          Issue could be drain angle, kink in the hose, crank case pressure
          Originally posted by priapism
          My girl don't know shit, but she bakes a mean cupcake.
          Originally posted by shameson
          Usually it's best not to know how much money you have into your e30

          Comment


            #6
            Originally posted by Northern View Post
            What's your oil pressure gauge/sensor setup (and is it logging through TS or is it just for a gauge)? Any chance it's not reading right - wrong sensor calibration in TS, counterfeit/knockoff sensor, etc?

            Your pressures may be a little higher just from running a heavier oil, but I don't think there's any issue with 20W50 unless temps drop below something like -10C

            Are those pressure readings both at idle? The cold start psi seems a little low, but some other threads have people saying cold start is that RPM as well.
            I don't think it would be the oil pressure relief in the block, it can't really make oil pressure go higher at idle.

            If the gauge isn't wrong, I think it could be the filter (clogged? wrong filter?) or a restriction/blockage in an oil passage somewhere because I don't see how it could make 65psi at warm idle without something restricting flow.


            For the turbine housing oil leak, it shouldn't matter what the oil pressure is as long as the drain is way bigger than the feed.
            No way should it be able to feed more into the turbo than a -12 drain line can remove.
            Issue could be drain angle, kink in the hose, crank case pressure

            Hi Northern, thanks for the questions and ideas! The temperature here is averaging 70 - 80 degrees outside.

            Are those pressure readings both at idle?
            When I first start the engine, the oil pressure gauge reads 40-45 psi. Then as the engine warms up getting to operating temp, the oil pressure gauge reads 60-65 and appears to be climbing if I don't turn off the engine. Both are at idle. While at 60-65, if I raise/increase the rpm, the 60-65 psi decrease to 50psi but as soon as my foot leaves the pedal and it goes back to idle, the it goes back to 60-65psi. I recently tuned my idle in tunerstudio, so it is idling at 800-1000 rpm.

            If the gauge isn't wrong, I think it could be the filter (clogged? wrong filter?) or a restriction/blockage in an oil passage somewhere because I don't see how it could make 65psi at warm idle without something restricting flow.
            I totally agree with you here. If this is what it is, I am just not sure where it could be clogged up (head was resurfaced and cleaned, block was inspected and cleaned, prior to assembly). The gauge is new, the sensor is new, and I changed the filter over the weekend. Yes, 65psi is a lot at idle! The only thing I did not check yet because I would need to take off the oil pan is the relief valve in the oil pump. Is there a way to check this without taking off the oil pan?

            For the turbine housing oil leak, it shouldn't matter what the oil pressure is as long as the drain is way bigger than the feed.
            No way should it be able to feed more into the turbo than a -12 drain line can remove.
            Issue could be drain angle, kink in the hose, crank case pressure

            I am using an HX40, along with the flexible steel oil return hose (3/4 inch diameter) that connects to the highest point of my oil pan (no leaks).
            I used a vanos oil housing so I can use the vanos feed hole to feed my turbo. I have the oil pressure sensor connected to a "T".
            As for crank case pressure, I removed crankcase vent on the valve cover and dumped to atmosphere, oil pressure is still the same.

            After thinking about it, I am leaning more towards the relief valve thats in my oil pump. I installed a used m52 oil pump, and this was the only part that I didn't open up, inspect, and clean; i assumed it was in good working condition since it rotate freely/nicely and no noise coming from it.

            Comment


              #7
              I just don't see how the oil pressure relief on the pump could make the pressure increase, when the pump is only making enough pressure for 10~20 psi at idle on a warm engine.
              The relief valve should only be able to bleed off excess pressure above whatever it is set to.
              Originally posted by priapism
              My girl don't know shit, but she bakes a mean cupcake.
              Originally posted by shameson
              Usually it's best not to know how much money you have into your e30

              Comment


                #8
                Originally posted by Northern View Post
                I just don't see how the oil pressure relief on the pump could make the pressure increase, when the pump is only making enough pressure for 10~20 psi at idle on a warm engine.
                The relief valve should only be able to bleed off excess pressure above whatever it is set to.
                I read about the relief valve in the pump, but don't know much about it. If that is what it does, then I definitely have to relook at my oil system.

                What else could cause this high oil pressure? Leaking headgasket? cracked head? Crank/rod bearings installed incorrectly?

                Thanks!!!
                Last edited by mini612; 06-22-2021, 10:49 AM.

                Comment


                  #9
                  I don't know. It doesn't make sense that the idle pressure rises as it warms up

                  Like a compression leak that only happens once the engine is warmed up?
                  Originally posted by priapism
                  My girl don't know shit, but she bakes a mean cupcake.
                  Originally posted by shameson
                  Usually it's best not to know how much money you have into your e30

                  Comment


                    #10
                    Originally posted by Northern View Post
                    I don't know. It doesn't make sense that the idle pressure rises as it warms up

                    Like a compression leak that only happens once the engine is warmed up?
                    Yes, it doesn't makes any sense! i'll need to do a compression test on my cylinders. I have another engine that i was building as a back up, i think if things don't work out, i guess i'll be using that engine instead of this one.
                    I will be going through everything this evening. Will be looking at my pressure gauge to see if its wired correctly, taking off the VC and check the oil channels, I may drain the oil to see if theres anything, etc...
                    Last edited by mini612; 06-22-2021, 01:24 PM.

                    Comment


                      #11
                      If you think compression is leaking into the oil galleries with a cutring head gasket, do a leakdown test. I doubt that's the issue but I also doubt an incorrectly installed pressure relief valve would cause such a thing at idle unless M50s have a gross excess of pump flow capacity relative to the M20, which has just enough. Excess restriction to flow (where?), excess flow (how?), excess viscosity (no). The simplest explanation is a bad oil pressure sender or gauge with a temperature dependent failure, which is definitely possible; I've had a bad oil pressure gauge out of the box. And the turbo looks used, so it's more than slightly possible that its seals are tired. Confirm the pressure with a mechanical gauge.

                      As an aside; M54B30 pistons, the thinnest of the M5X pistons, for a turbo build? Are they aftermarket?

                      IG @turbovarg
                      '91 318is, M20B25 turbo
                      [CoTM: 4-18]
                      '94 525iT slicktop

                      Comment


                        #12
                        Originally posted by varg View Post
                        If you think compression is leaking into the oil galleries with a cutring head gasket, do a leakdown test. I doubt that's the issue but I also doubt an incorrectly installed pressure relief valve would cause such a thing at idle unless M50s have a gross excess of pump flow capacity relative to the M20, which has just enough. Excess restriction to flow (where?), excess flow (how?), excess viscosity (no). The simplest explanation is a bad oil pressure sender or gauge with a temperature dependent failure, which is definitely possible; I've had a bad oil pressure gauge out of the box. And the turbo looks used, so it's more than slightly possible that its seals are tired. Confirm the pressure with a mechanical gauge.

                        As an aside; M54B30 pistons, the thinnest of the M5X pistons, for a turbo build? Are they aftermarket?


                        Hey Varg, you are absolutely right regarding the oil sender. I replaced the oil pressure sender and the gauge is reading correctly now.
                        I am using M54b30 pistons because i have them laying around. They were from m50 stroker projects that i've completed over the years. I was also trying to bring down the compression without using aftermarket parts. So what I came up with is s50 crank with nonvanos 135mm rods with M54b30 pistons, gives me around 8:5.1 (can't remember the exact compression numbers but its very close). And yes, i had all these parts from previous projects. I am not planning on achieving high hp numbers, i'm content with 400. All the parts for this motor is what i already have and the only things I really did spend money on was the megasquirt 2 v3 kit, cutring headgasket, bearings, piston rings, clutch, the little things: oil feed line/return line etc... The HX40 is used, got it on a trade, no shaft-play but I probably should've totally rebuilt it (replaced the clip and took it apart to clean but not a true rebuilt) before slapping it on, been driving the car and no oil is leaking from it .

                        Did a cylinder compression test over the weekend. I completed this process 2x and weird how the numbers are almost exactly the same +/- .5:
                        1 - 150
                        2 - 150
                        3 - 149
                        4 - 151
                        5 - 150
                        6 - 151

                        All in all, the engine runs good. Now it just needs a tuning. Been driving it around the block a few times, other than an exhaust leak (my welding is not good!), there's no other leaks.
                        Last edited by mini612; 06-30-2021, 07:55 PM.

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