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Help Me Choose M20 Stroker Configuration (crank, pistons, rods)

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    #16
    You are correct, I typed in reverse. :/

    Yeah I did the math a while back and figured it wasn't worth worrying about.
    john@m20guru.com
    Links:
    Transaction feedback: Here, here and here. Thanks :D

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      #17
      Spoke to Bimmerheads yesterday - I think I will go with 84mm stroke, IE Mahle “ultimate street stroker” pistons, and they recommended the heavier duty Molnar rods. And looks like they would be able to ship in about a week.

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        #18
        Originally posted by mikey.antonakakis View Post

        Did not do the math on it, but just did - maybe about 2deg? (I'm making assumptions about cam sprocket diameter). So, pretty minor.
        I trust your dyno results much more than any heuristics I've heard, but I always heard that advancing the cam moves the powerband lower, also seen in dyno tests in the video below - warning, GM content ;)
        Although for a 2deg difference in this case, probably doesn't matter much lol.

        Not a single cam motor like an M20, but garage4age has the best back to back dyno tests. https://www.youtube.com/watch?v=bnIsNwdKnCw

        Engine masters does some decent testing too but most of it is geared toward the classic domestic crowd and they haven't done any cam timing tests.

        IG @turbovarg
        '91 318is, M20 turbo
        [CoTM: 4-18]
        '94 525iT slicktop, 3L M50 + BW S366 project

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          #19
          garage4age is a great channel!

          IE 2.9L Ultimate Street Stroker pistons, 84mm crank, spacer/bolt/washer, ARP main studs, and Molnar rods ordered! Took a peek at the donor short block today, it’s oily/crusty, but should clean up really nice.

          ForcedFirebird the intermediate shaft bearings looked to be in good shape (see attached), but will definitely defer to your advice on whether they should be replaced.
          Attached Files
          Last edited by mikey.antonakakis; 09-23-2022, 06:54 PM.

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            #20
            Can't tell by eye, unless they are totally wiped. Check the clearance on the intermediate shaft, but in all honesty, why would you rebuild and NOT change them? It's a few hundred bucks that could potentially trash a couple thousand in parts.....in about .000001 seconds.
            john@m20guru.com
            Links:
            Transaction feedback: Here, here and here. Thanks :D

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              #21
              Originally posted by ForcedFirebird View Post
              Can't tell by eye, unless they are totally wiped. Check the clearance on the intermediate shaft, but in all honesty, why would you rebuild and NOT change them? It's a few hundred bucks that could potentially trash a couple thousand in parts.....in about .000001 seconds.
              PM with bearing order coming shortly!

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                #22
                Originally posted by ForcedFirebird View Post
                Can't tell by eye, unless they are totally wiped. Check the clearance on the intermediate shaft, but in all honesty, why would you rebuild and NOT change them? It's a few hundred bucks that could potentially trash a couple thousand in parts.....in about .000001 seconds.
                Please explain what happened if shaft clearance is out?

                Is there symptoms to indicate failure?

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                  #23
                  Ones I’ve seen fail have flaked / spalled and some have worn through. If clearances are too large the oil pressure will be lower as the oil “escapes” too quickly out the bearing (the oil pressure is actually the back pressure)
                  89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                  new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

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                    #24
                    Originally posted by ADEN View Post

                    Please explain what happened if shaft clearance is out?

                    Is there symptoms to indicate failure?
                    The intermediate shaft is at the front of the engine, right next to the oil pump - If the tolerance is loose, then you are going to starve the rear of the engine.

                    Originally posted by digger View Post
                    Ones I’ve seen fail have flaked / spalled and some have worn through. If clearances are too large the oil pressure will be lower as the oil “escapes” too quickly out the bearing (the oil pressure is actually the back pressure)
                    Stock bearings are a stamped steel ring with cast babbitt, there is no indicator that they have worn.

                    Front bearing should measure <1.496" (38mm), rear <1.437" (36.5mm). The rear is kind of a pain to measure, I use a telescope bore gauge and lots of patience.
                    john@m20guru.com
                    Links:
                    Transaction feedback: Here, here and here. Thanks :D

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                      #25
                      My oil light is not on and never comes on .Is that indicate i have a good oil pressure?

                      Oil light turn off after 2-3 seconds of cranking is that ok?

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                        #26
                        Originally posted by ADEN View Post
                        My oil light is not on and never comes on .Is that indicate i have a good oil pressure?

                        Oil light turn off after 2-3 seconds of cranking is that ok?
                        The only way to check oil pressure is to measure it with a gauge.
                        The oil light (~7psi iirc) will only come on while driving in a catastrophe failure so you probably won’t notice lower than normal pressure depending how much lower ( how worn) it is. It may or may not come on at idle, it depends what viscosity oil is used and the temperature it sees but with xxw-40/50 and hit oil you would most likely see light on
                        Last edited by digger; 09-28-2022, 02:01 PM.
                        89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                        new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

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                          #27
                          To add to what digger said, my oil pressure at 900rpm idle after 60 miles of 80-90mph at ~85F ambient temperature is 20psi (i.e. about the hottest my oil would get other than lapping a race track). This is measured after my oil filter and oil cooler, which causes a lower pressure reading compared to measuring straight out of the oil pump. I'm running LiquiMoly 10W-60, I believe this is very similar to BMW Twin Power Turbo 10W60.

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                            #28
                            When i was using 10W-40 mineral oil maybe 7-8 years ago, during one heat wave 115F with A/C on idling at 950-1000rpm and stuck in traffic for an hr my oil light started to go on at idle (i have the VDO pressure sender with 8psi switch). The coolant temp was around 102C.
                            i now use 10W-40/50 penrite full synthetic depending on season and gauge at worst indicates 10-15psi. I have temp sensor in the pan (will change that) so dont pay much attention to it as i get a better indication of temp from the pressure gauge.
                            This is on an engine that has done a bit above 100k miles on 3.1L stroker reusing the intermediate shaft bearings (not sure how many km on the original block) but they were mint no visual signs of wear at all despite signs of the owner not changing oil very often, unlike another block where it has flaked apart and you can visually see wear patterns after 125k miles with regular oil changes.
                            89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                            new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

                            Comment


                              #29
                              Originally posted by digger View Post
                              When i was using 10W-40 mineral oil maybe 7-8 years ago, during one heat wave 115F with A/C on idling at 950-1000rpm and stuck in traffic for an hr my oil light started to go on at idle (i have the VDO pressure sender with 8psi switch). The coolant temp was around 102C.
                              i now use 10W-40/50 penrite full synthetic depending on season and gauge at worst indicates 10-15psi. I have temp sensor in the pan (will change that) so dont pay much attention to it as i get a better indication of temp from the pressure gauge.
                              This is on an engine that has done a bit above 100k miles on 3.1L stroker reusing the intermediate shaft bearings (not sure how many km on the original block) but they were mint no visual signs of wear at all despite signs of the owner not changing oil very often, unlike another block where it has flaked apart and you can visually see wear patterns after 125k miles with regular oil changes.
                              Thanks a lot, I will try to replicate your situation of hot engine idling long time then will take pressure readings, the problem now is that i have to find a measuring device that will fit in the stock oil switch threads or maybe fabricate an adapter to fit a Toyota sensor (as a budget solution) or any stock pressure sensor.

                              Btw, Will the m5x oil pressure sensor fit in m20 oil switch hole with no modifications?

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                                #30
                                We would see oil pan temps upwards of 300f on summer track days. We used to run Mobil 1 15w50 and would have a hot idle of about 8psi on a stock engine, changed to LiquiMoly 10w60 and we saw an ~8psi increase. That was a long time ago, we now modify the oil systems and will see 90psi cold, and ~22psi hot idle, 85psi at the rev limiter hot.
                                john@m20guru.com
                                Links:
                                Transaction feedback: Here, here and here. Thanks :D

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