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Anatomy of a bulletproof S52?

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    Anatomy of a bulletproof S52?

    I put this in the Track section, then realized it probably belongs here.

    I think I am going to rebuild the S52 in my E30 track car over the winter.

    More power, while I wouldn't say no to it, is not the primary goal here; what I am trying to do is add reliability.
    I want to know that I can hammer on the car now and forever, and she'll keep coming back for more. She is an HPDE toy, not an all-out racecar, although she has a welded in half cage, gutted interior, etc. She's pretty hardcore, but as I am not racing her, I don't need every last bit of power.

    I understand that using the car in this manner will cause more wear and tear on the motor, and I know that lack of maintenance, 'money-shifting' and time will still cause damage to motor, no matter how you build it. But, what I want to do is build the strongest S52 'endurance' engine that I can.

    So, what areas should I be considering? Eagle rods? Solid lifters? Dual Valve Springs? Forged Pistons? Coated bearings? ARP head studs & crank studs?

    Some history that may be relevant:
    This is a normally aspirated S52, converted to OBD1. Stock cams. M50 intake manifold, OBD2 exhaust manifolds with the secondary O2 injection ports welded up. 413 red label DME running a TRM chip for 91 octane, M50 manifold, standard weight flywheel 21.5# injectors - all the things my car has.

    Metric Mechanic did some minor work on the head a couple of years ago (skimmed it very slightly, added stronger valve retainers, new valve guides & seals, and replaced a couple of valves, as the motor had been left sitting and there was some corrosion/pitting on 2 of them).

    The motor has standard pistons with oversize rings. A hone was done at a machine shop to clean up some minor pitting & corrosion on the cylinder walls.

    I'm handy with a wrench, and know how to time VANOS, etc. I will not necessarily be building this motor myself. I figure at least getting the rotating assembly balanced is a good start.

    Please give me your thoughts on this build! Thanks guys!
    Kingston
    Originally posted by LJ851
    kingston is the play by play announcer for this thread.
    ‘Tis by the grace of God that my cars run!

    Originally posted by unloadedak
    #teamross
    Siobhan's Build Thread - UPDATED!


    #2
    new stock pistons, new stock rods. new stock everything including hardware.

    as minimal aftermarket parts as possible

    BMW makes the best enduro spec BMW engines; run it 100% stock
    OBD1 M54/M52TU swap as a M50b25

    Z4 non powered steering rack fits e30



    Euro e46 2005/6 320d 6mt gearbox into E30 with M20 hardy and beck 1985 327s engine

    Comment


      #3
      Originally posted by Wanganstyle View Post
      new stock pistons, new stock rods. new stock everything including hardware.

      as minimal aftermarket parts as possible

      BMW makes the best enduro spec BMW engines; run it 100% stock
      I second this also. But his block is junk already had to hone it.

      Comment


        #4
        Originally posted by DesertBMW View Post
        I second this also. But his block is junk already had to hone it.
        Buy NEW oversize single or double oversize pistons; BORE the block.

        BMW blocks should NOT be honed ever; if the cylinder looks no good it needs to be bored upsize and the old piston tossed.
        OBD1 M54/M52TU swap as a M50b25

        Z4 non powered steering rack fits e30



        Euro e46 2005/6 320d 6mt gearbox into E30 with M20 hardy and beck 1985 327s engine

        Comment


          #5
          If you want bulletproof, backdate to a 3.0. It's a much more durable motor. The S52 crank has some nasty harmonics. (This is shared with the M54B30.)
          2006 GMC Sierra 2500HD 4WD LBZ/Allison
          2002 BMW M3 Alpinweiß/Black
          1999 323i GTS2 Alpinweiß
          1995 M3 Dakargelb/Black
          - S50B32/S6S420G/3.91
          1990 325is Brilliantrot/Tan
          1989 M3 Alpinweiß/Black

          Hers: 1996 Porsche 911 Turbo Black/Black
          Hers: 1988 325iX Coupe Diamantschwartz/Black 5spd

          sigpic

          Comment


            #6
            Originally posted by nrubenstein View Post
            If you want bulletproof, backdate to a 3.0. It's a much more durable motor. The S52 crank has some nasty harmonics. (This is shared with the M54B30.)
            then the argument can be made for going down to 2800cc.

            84 bore will blow even less head gaskets and the shorter stroke will take higher rev's

            its also much cheaper and takes BOOST much better than 3,000 or 3200
            OBD1 M54/M52TU swap as a M50b25

            Z4 non powered steering rack fits e30



            Euro e46 2005/6 320d 6mt gearbox into E30 with M20 hardy and beck 1985 327s engine

            Comment


              #7
              There are two major things you have to guard against to make an engine durable on track:
              Extended time at high temps - this requires adjustment of certain clearances like piston to bore, piston ring end gaps, etc. as well as a SAFE tune.
              Extended time at high RPM - this is the primary way things break; you'll need to blueprint bearing clearances, and fix specific weaknesses like the oil pump drive.

              As Wanganstyle said, BMW does the best job building BMW engines for endurance. There's a HUGE amount of validation testing that you get to take advantage of when using stock parts. Use that engineering and testing background wisely whenever you can.

              These are the things I'd look at immediately:

              #1: Ring gap. Extended time at high output will put a LOT of heat through the tops of the pistons, which will cause the rings to expand. If the gap isn't sufficient, then the ring ends will but and either scuff the bores, pop the tops off the pistons or both.
              Since the block has been honed and rings swapped out, your ring gaps are a MAJOR RISK.

              #2: Oil pump. As mentioned, the S52 shares a crank with the M54B30, which is known for shearing the oil pump drive from extended time at high RPM. Spend money on a race oil pump drive shaft/sprocket.

              Other parts: As Wanganstyle said, stick with stock parts except to correct previously identified deficiencies, like the oil pump.

              The block isn't "junk" because it's been honed. If it wasn't honed with a torque plate, the roundness of the bores is questionable. The extra piston to bore clearance may actually be beneficial for an engine that sees significant track duty, as it helps guard against bore scuffing due to overheating of the piston crowns from extended time at high load.
              However, stock replacement standard overbore pistons (and rings) are obviously not available for non-standard overbores.

              Comment


                #8
                Kingston, long time no talk.

                Since you had to hone to clean up cylinder pitting, then reused stock sized pistons, you likely have excessive cylinder to piston clearance. This will cause oil consumption, piston slap and low power. I tried the same thing on an M20 once (actually twice) and the engines ran terrible; I ended up re-building both engines again with .020" over pistons. At this point, you have no choice but to go with oversized pistons. This is a good thing, because piston choice will be critical in designing your build. I just built an S52 with Metric Mechanic Sport pistons, stock rods, stock cams, but completely rebuilt from top to bottom. I haven't finished the swap into my MTech I street car, but should have it up and running in a few months (hopefully less). I expect this to be a fun and reliable setup, but didn't design my engine build with track time in mind because that's what my Spec E30 is for.

                There are a lot of options, but no matter what you should do the following things.
                1)Install the new bimmerworld 4 bolt oil pump shaft (http://store.bimmerworld.com/gsr-m52...aft-p2210.aspx). This is a newer piece and better than the wire tied nut as the stock shaft tends to break even when the nut is tied.
                2) Use Clevite coated rod bearings. Don't use coated main bearings (I prefer Kolbenshcmidt) as un-coated bearings have the ability to embed contaminants should they make it through the oil filter and pump.
                3) Use a hard anodized forged piston as they should last a really long time.
                4) Invest effort into the cylinder head with higher performance lifters and the proper valve spring for your cam and desired RPM. You'll need to consult Metric Mechanic/VAC/BW for recommendations but the valve train is what is limiting your high RPM capability (short bursts).

                You should realize that the S52 89.6 mm crankshaft suffers from extremely harsh harmonics and no amount of balancing is going to help above 7K RPM or so. ATI makes a very expensive harmonic balancer that might help, but I'm not convinced this will help that much. To be honest, I wouldn't even worry about balancing the stock crank; pistons and rods should of course be hand balanced.

                My ideas:

                Option 1 "money no object" - Use Metric Mechanic Rally pistons with their custom 138mm rods (similar to Eagle). The increased rod ratio will reduce piston acceleration just a smidge and help it rev a little easier, but the S52 crankshaft harmonics will prove problematic if you rev much beyond 7K in the long term.

                Option 2 "high rev build" - Use a crankshaft from M52 (84 mm), M44 rods (140 mm), and a custom piston designed to get 11.5:1 compression. Stock S52 is really only 10:1 based of actually measurements. Racetep.com or Metric Mechanic should be able to help with pistons; again, recommend hard anodizing. You could use custom rods (several outfits can make them for you), but the M44 rods are pretty light and the increased length, combined with the better crankshaft, should make this motor rev reliably. The decrease in displacement will obviously cost in the power department.

                Option 3 "What Rich would do" - Rebuild with oversized pistons from MM or Racetep and simply don't rev the motor past 7K. This should prove reliable for years.

                Comment


                  #9
                  i'd use ACL bearings if not going with OEM KS
                  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
                    I'm a firm believer in bmw engines and the reliability internally. But why not use Arp main studs?

                    If you have them done right meaning taking it to a shop and having it line honed with the studs it insures the main bores to be true. Also you could then re-torque if need be without having to be concerned about tty bolts.

                    I'm not trying to start a huge debate, but curious why would you recommend not using them?

                    I've personally used them In every engine I've built even stock engines, I'm an apprentice engine builder so I don't have a cost of labor.

                    Comment


                      #11
                      Originally posted by richard.bratton View Post
                      Since you had to hone to clean up cylinder pitting, then reused stock sized pistons, you likely have excessive cylinder to piston clearance.
                      Excessive for what use? We don't know how much it's been honed.
                      If the stock clearance is .0015 and it's been honed .001 (admittedly unlikely) that's probably an improvement for track use as it gives extra safety margin for thermal expansion of the pistons. If it's been honed .005 (more likely) that's excessive for hypereutectic pistons.

                      Comment


                        #12
                        Originally posted by The Dark Side of Will View Post
                        Excessive for what use? We don't know how much it's been honed.
                        If the stock clearance is .0015 and it's been honed .001 (admittedly unlikely) that's probably an improvement for track use as it gives extra safety margin for thermal expansion of the pistons. If it's been honed .005 (more likely) that's excessive for hypereutectic pistons.
                        Agree with all except that a larger clearance would be a performance increase for track use. In the 15 or so Spec E30 engines I've built, I've run clearances from .0017" to .0035" with success. Some of my better dyno performing engines were on the tight side; the cast hypereutectic pistons just don't expand much. Anything above .0035" and oil consumption becomes a problem.

                        I think it's very unlikely that the machine shop only removed .001", but I could be wrong...

                        Comment


                          #13
                          Woah, hadn't checked back here in a bit. Thanks to everyone who posted in the thread. We ran compression & leakdown tests on the motor, and they numbers came back surprisingly healthy. I'm still planning to upgrade some things for the spring, and may well bore the motor (either buy or rent a toque plate from VAC) and run forged pistons.

                          I'm going to re-read all this a few times and try to get a plan together.

                          Rich, good to hear from you man. Jealous that you have an MTech 1 car! We'll have to catch up more soon.
                          Originally posted by LJ851
                          kingston is the play by play announcer for this thread.
                          ‘Tis by the grace of God that my cars run!

                          Originally posted by unloadedak
                          #teamross
                          Siobhan's Build Thread - UPDATED!

                          Comment


                            #14
                            Originally posted by richard.bratton View Post
                            Agree with all except that a larger clearance would be a performance increase for track use. In the 15 or so Spec E30 engines I've built, I've run clearances from .0017" to .0035" with success. Some of my better dyno performing engines were on the tight side; the cast hypereutectic pistons just don't expand much. Anything above .0035" and oil consumption becomes a problem.

                            I think it's very unlikely that the machine shop only removed .001", but I could be wrong...
                            I didn't mean that the larger clearance would be a performance improvement... but that it could be a reliability improvement, specifically against running the piston crowns too hot.

                            Comment


                              #15
                              Originally posted by Wanganstyle View Post
                              new stock pistons, new stock rods. new stock everything including hardware.

                              as minimal aftermarket parts as possible

                              BMW makes the best enduro spec BMW engines; run it 100% stock
                              This is a post that I have great interest in, realize it is only 4 years old. I figure my question in this thread would give those who are planning on running a bullet proof M52 a pretty definitive idea of what a racer is looking at to build a bullet proof M52 endurance racing motor.

                              I am preparing my Spec E30 to go World League Racing (WRL) in the Texas area. So far my 10 years racing has been in as “near” to stock powered cars, Spec Miata and Spec E30. The WRL classes my Spec E30 as it sits in GP2. The rules will allow an engine swap and keep me in the GP2 class. To stay in the class the swapped motor has to dyno out at 197 HP without adding ballast and if I add up to 150 lbs of ballast and stay out of the ballast modifier points. If it is a stock engine I can produce the HP numbers from the manufacture and I am not required to do a dyno. So... I believe a stock M52TU28 becomes the right engine to swap.

                              Of course finding one to do the swap means an engine with over 100K, with questionable maintenance. Hence an engine rebuild I most likely required. Again going WRL racing and have a HP goal of stock and a reliability goal of 8 hours of straight racing one day and 8 the next. I see that a few folks in this thread have racing experience and understand the environment. I don't have experience with a M52 in an endurance environment, nor do the friends I race with.

                              So stock everything or selective aftermarket parts, like rods, bearings, valves or different springs or???

                              Thanks in advance.
                              Last edited by DTedeschi; 07-08-2018, 06:30 AM.

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