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Frankstein's engine (M42/M44/S50)

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    Frankstein's engine (M42/M44/S50)

    Hi there.
    here is my build and i hope i will find some people able to help me out with my issues.

    first things first, here is a non exhaustive list of the engine parts.

    - M44 block with M44 crank

    - E36 M42 head, ported, oversize valves and upgraded springs with titanium retainers and solid lifters

    -Catcams 272° intake cam with and stock exhaust one (i actually have 290°/272° but afraid i will loose to much driveability at low RPM with this setup)

    - Custom intake with 70mm throttle body

    - piston wise i currently have standard euro S50B30 pistons , 12.5CR forged S50B30 pistons ordered waiting to be received.

    - rods are M44, rebushed to 21mm

    - main and rods bearing are ACL

    -engine management is a KDATA ECU PNP on the M44 loom.


    I did some measurement on the engine but by lack of experience i have a hard time interpreting the results.
    crank main journals are all close to 59.98mm (some must be 59.978) so that should be corresponding to the Green bmw standars (between 59.977 and 59.983)

    I did a test with plastigauge and found close to 0.10 bearing play (that should be divided by 2 to spread to each side of the journal) so 0.05

    I also did measurement (becuse i wasn't sure about the plastigage thing) with what we call a "3 touchs" inner micrometer here in france with the bearings in place, torqued down to spec but without the crank obviously to be able to measure. i found close to 60.07 for 4 of the bearings and 60.09 for the one with the trust bearing.
    (did the same with an old bearing and found 60.025)

    so i get pretty close to the 0.1mm play, so oil film will be between 0.045 and 0.05mm. what do you guys think? BMW technical data say "radial cranshaft bearing play between 0.020 and 0.046"

    regarding rods i only checked one the same way and found 0.05mm bearing play (so 0.025mm on each side of the rod journal)

    also i have an issue with my compression ratio. i did volume measurement and found around 33cc for head combustion chamber and 24cc for piston and head gasket (1.8mm) volume.
    S50B30 pistons have 1.2mm higer compression height than M44 (31.6 for s50 30.4 for M44) I shaved 0.7mm and rod have an offset of 0.5mm to have the same overdeck as standard.... yeah that sound weird and it's my mistake, I listened to a guy for this and i shouldn't have i think.

    so that give me a 57cc combustion volume, and with the 485cc given by 83.5mm stroke and 86 bore it result in a CR of 9.5... aiming between 12 and 12.5 to compensated the higher duration cams that will close the intake valve later (12 static CR will give me around 10.4 / 10.5 dynamic CR)

    SO yeah, piston volume is way too big, that why i ordered 12.5CR forged S50B30 pistons that comes with a small volume hoping that i will be able to make everything work and have a decent RV.

    thats all for now. will post pictures and more stuff tomorow.

    #2
    no interest for my post in a week? i guess you guys are not interested in a low hp engine like mine

    Comment


      #3
      Originally posted by IlovM42 View Post
      thats all for now. will post pictures and more stuff tomorow.
      I was waiting for the pictures and other stuff.

      Comment


        #4
        And bearing clearance from bmw are diametric clearance not on the radius
        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


          #5
          thanks to confirm that point DIGGER. that means that clearances are 2 times bigger than the maximum clerance allowed what's weird is that the engine builder that did the head told me that 0.1mm diametral clearance is a little low for an engine that should rev close to 8Krpm. i don't have enough experience to talk about that hence my question here.


          here to give you guys some interest in the build. Btw i just remembered i've seen those smileys ​​totally true my bad.

          i had the engine for about 5 years now and it have been laying in boxes in pieces so first step have been to fully assemble it (without pistons and rods) to check if i have everything, find where every screws goes and list what i needed to buy.



          head have been sent in UK to a skillfull guy who ported it and installed bigger valves.









          and i also ordered from him this nice little intake.







          the S50B30 euro pistons skimmed 0.7mm and lowered 0.5mm with the rod bushing.


          but hey are giving me issues with my CR as i don't have what i'm expecting. ordered this that should resolve the problem.

          Comment


            #6
            0.1mm is 0.0040” which is way too loose for even main bearings. Are you sure it’s correct ?new parts proper torque sequence etc? Normally it works pretty much in spec
            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


              #7
              Subscribed. Definitely interested in an M42/4 build.

              Comment


                #8
                Originally posted by digger View Post
                0.1mm is 0.0040” which is way too loose for even main bearings. Are you sure it’s correct ?new parts proper torque sequence etc? Normally it works pretty much in spec
                well i measured in 2 different ways. first with pastiguage and it gave me beetween 0.1 and 0.13mm clearance. As i wasn't sure about doing it properly i removed the crank and measure it so i'm confident with those values (between 59.975 and 59.985mm) according to BMW TIS that should correspond with standard green bearing. maybe my mistake is that i ordered standard ACL bearing and should have ordered -0.025 ones to reduce clerance, forgot to say that i measured with an old bearing and got 0.045 clearance.

                Logic would be to get into BMW bearing clerance recommendations but where i'm lost is that the engine builder told me that 0.1mm clearance is tight for an engine that's going to rev.... I am too inexperienced to know what to do on this two contradictory things. engine builder is well known in UK, he build lot of BMW 4 cyl and even race one and have M44 screaming all the way up to 8000rpm so he know his stuff...

                Victell thanks. In US or UK you are luckier than us here as we are not allowed to modify a car... that's why i didn't went FI because in a E30 the turbo is too obvious under the hood... and didn't want a bigger engine to keep the spirit of the 318is lighter front end than a 325 for example.

                Comment


                  #9
                  yep something up with the ACL's would be my bet given the old one is about spot on
                  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


                    #10
                    you want the piston top flat surface to be 1.00 mm +/-0.1 from the cylinder head flat surface so if the gasket is more than 1.00 mm thick the piston needs to stick out a bit. E.g with 1.75 mm gasket the piston needs to stick out 0.75 mm

                    with the rod small end bush did you get them offset bored?
                    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


                      #11
                      i did mistake with the first setup so i'll be more carefull with the forged pistons.

                      what's your advising me is to pay more attention to the squish than the above deck value if i understand correctly. for the little I know the squish will have good effectes on the air fuel mixture for a N/A engine so i',ll learn about that and try to improve it.

                      yes the rod small end bushes have been replaced and bored with a 0.5mm offset. what have been a mistake with the stock S50B30 euro piston might be a good thing with the forged ones. logic was that by lowering the whole psiton by 0.5mm i have extra clerance on the valves pockets and needed to remove less material from the top of the piston to avoid weakening it too much. sound stupid now as i saw people removing like 3mm from those piston to fit with 88mm stroke crank.

                      so with old setup i was having a low CR and needed to raise it. possible by decking the block/head for example but refused myself to go this route
                      with new setup i'm gonna have a high CR that gonna have to be reduced. that gonna be in my opinion a lot easier and better. i'll be able to reduce the pistons height, increase the piston volume by machinng the dome in the middle, and adjust with head gasket tickness if needed.

                      i'll do my math and measurement carefully with new pistons before doing anything i can't undo. try and learn from your mistakes is the way to acquire knowledge

                      Comment


                        #12
                        You want proper squish with suitable cr. I wouldn’t go nuts with cr on pump fuel. You can also get mls head gasket in many different thicknesses and bores.

                        what is
                        - deck height
                        - rod length
                        - compression height
                        - proposed gasket thickness and bore
                        - piston cc for forged ones
                        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


                          #13
                          stock numbers for M44 are as follow:
                          block height 212mm
                          stroke 83.5mm
                          rod 140mm
                          CH 30.4mm
                          stock HG thick. 1.8mm
                          with some math that give 0.15 above block (83.5/2 + 140 + 30.4 = 212.15

                          my setup
                          block height 212mm
                          stroke 83.5mm
                          rod 139.5mm
                          CH 31.6mm (right now my pistons are 30.9mm as i removed 0.7mm)

                          with untouched S50B30 pistons that should give 0.85 above block (83.5/2 + 139.5 + 31.6 = 212.85) and with my pistons skimmed 0.7mm 0.15 above block (83.5/2 + 139.5 + 30.9 = 212.15)

                          currently head volume have been measured at 34cc (worth doing another measure later, actually will have to after i skimmed the head to remove a scratch that happened during shipping.

                          measured piston volume with 1.8mm head gasket at TDC is 22cc

                          V=485.04cc v=22+33=55cc that give CR = (V+v)/v = (485.04+55)/55 =9.81:1

                          i agree that if i hadn't skimmed the pistons 0.7mm piston + head gasket volume would be smaller as the pistons enter into the HG volume but wouldn't be enough and hard to do an estimation of the volume gained like this.

                          If i hadn't lowered the small rod bushing i would have an extra 0.5mm above deck to play with. My mistake again to do that before taking measurements

                          volume of forged pistons is 4.3CC for the 12.5CR i ordered (11.5CR was an optino with volume of 7.3cc)

                          now did i made a mistake again by ordering the 12.5 and not the 11.5 ones. well possible but again my logic was that i'll be able to increase the volume of the piston by machining it (in a better way than previously) and then lower CR

                          Comment


                            #14
                            Originally posted by IlovM42 View Post

                            with untouched S50B30 pistons that should give 0.85 above block (83.5/2 + 139.5 + 31.6 = 212.85) and with my pistons skimmed 0.7mm 0.15 above block (83.5/2 + 139.5 + 30.9 = 212.15)
                            0.85 mm above deck was/is about right with 1.8 gasket.

                            with 4.3cc pistons i get your CR to be 11.5:1 assuming the pistons CH is 31.6mm and 1.8mm HG which is the upper end of what you want IMO with baby cams. (presumably the 12.5 and 11.5 you refer to is when used on a S50)
                            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


                              #15
                              Have you cc'ed the piston? The Mahle site just gives dimensions for the 286 horse S50. S50 shows 71x3.72.dish. Assuming a 10.7cc head gasket, where are you getting the other 13.3cc? Mahle does show volume for M42 and M44. M42 is 70.2x3.5 at 7.2cc which is close to your dish dimensions before milling.

                              Comment

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