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    • BMW's new X3M/X4M S58B30T0 motor does not share bore x stroke or compression ratio with B58/B48/B38 engine family, new design - Specifications, pictures, dyno

      The entire point of BMW's B-Series engine range is that it is modular. That means from the 1.5 liter B38 inline-3 up to the 3.0 liter B58 inline-6 all the engines share the same bore and stroke meaning they can share the same pistons and rods.


      Not so with the new S58 powering the F97 X3M and F98 X4M (and upcoming G80 M3). That means the block is different, the bore x stroke ratio, as well as the engine internals:

      Engine Displacement Bore Stroke Application
      S58 2993cc 84mm 90mm X3 M/X4 M/G80 M3
      B58 2998cc 82mm 94.6mm 2er/3er/4er
      S55 2979cc 84mm 89.6mm F80 M3/F82 M4
      N55 2979cc 84mm 89.6mm 2er/3er/4er
      S63 V8 4395cc 89mm 88.3mm M5/M6/X5 M/X6 M
      N63 V8 4395cc 89mm 88.3mm 5er/6er
      You will notice the N54, N55, and S55 all share the same bore x stroke. They are not the exact same thing as the S55 has a closed deck block but those engines are all the same basic engine family and architecture.

      Why is BMW increasing the bore and reducing the stroke in the S58? Well, it may be because they intend to rev it out a bit as the press release states a forged crank and redline of 7200 rpm.

      Piston speed at 7200 rpm with 90mm stroke: 4251.96 FPM
      Piston speed at 7200 rpm with 94.6mm stroke: 4469.29 FPM

      It is still an undersquare design but they did reduce stroke by almost a full 5mm. BMW is reducing stress at higher RPM a bit.

      To make up for the lost displacement from reducing the stroke, they increased the bore by 2mm. Is this a good thing? Traditionally in BMW M language it means thin cylinder walls. It is too early to know for sure but based on the photos of the block it certainly looks like BMW left enough material for it to take some punishment.

      BMW also lowers the compression ratio for the S58 to 9.3:1 from the 11.0:1 in the B58. That is quite the drop meaning expect big boost up top. Response down low will not be quite as good but this is supposed to be an M motor that revs for power, right?

      BMW's dynograph for the Competition version is interesting showing peak power at 6000 rpm which holds to redline but teh the torque curve also drops at 6000 rpm:


      What other changes?

      - 350 bar fuel pressure
      - Revised intake
      - New oil pan
      - New oil cooler
      - Revised intercooler
      - 3D printed cylinder head

      BMW touches on the new head:

      Quote Originally Posted by BMW
      the cylinder head has a core manufactured using 3D printing. This additive manufacturing process enables geometric forms to be created that are beyond the capability of conventional metal casting techniques. 3D printing technology has cut the weight of the new engineís cylinder head core and allows its coolant ducts to be routed in a way that optimizes temperature management.
      What does this mean for the G80 M3? Well, let's not just assume the S58B30T0 goes right in. BMW with the S63 twin turbo V8 modified the motor into the S63TU for the F10 M5 increasing the boost and redline.

      BMW could do the same here although it is unlikely due to the X3M/X4M and G80 M3 sharing all wheel drive and the same transmission. The wild card is the G80 M3 pure.

      The 8-speed automatic limits BMW to 7200 rpm despite peak power said to come at a 7300 rpm redline. The 'Pure' edition of the M3 will have a manual transmission so it is entirely possible we will see a higher revving S58 variant in it. That would be a nice nod to classic M fans but do not get your hopes up.

      Regardless, the S58 is not just a B58 with bigger turbos and more boost that revs a bit higher. BMW actually made some significant changes.




















































      This article was originally published in forum thread: BMW's new X3M/X4M S58B30T0 motor does not share bore x stroke or compression ratio with B58/B48/B38 engine family, new design - Specifications, pictures, dyno started by Sticky View original post
      Comments 12 Comments
      1. quattr0's Avatar
        quattr0 -
        The question is this or proven twin-turborcharged V-8 GLC63? They are both with same starting price at $70k+.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by quattr0 Click here to enlarge
        The question is this or proven twin-turborcharged V-8 GLC63? They are both with same starting price at $70k+.
        If your goal is power, the GLC63. The X3M is not even on the market and a turbo upgraded GLC63 can smoke a Ferrari 812 Superfast: https://www.benzboost.com/content.ph...-812-Superfast
      1. Tony@VargasTurboTech's Avatar
        Tony@VargasTurboTech -
        Very interesting, and cool. Thanks for posting
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Tony@VargasTurboTech Click here to enlarge
        Very interesting, and cool. Thanks for posting
        It's what I do.
      1. Eleventeen's Avatar
        Eleventeen -
        Three points of interest for me:

        1) BMW actually built an ///M specific engine (which I thought they said they weren’t doing anymore).
        2) Looks like they went with the integrated exhaust manifold like the B58.
        3) Check out the 4 bolt crank snout. No more spun hubs!
        4) I think the timing system is at the rear of the motor now, so we’ll see how that holds together.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Eleventeen Click here to enlarge
        3) Check out the 4 bolt crank snout. No more spun hubs!
        4) I think the timing system is at the rear of the motor now, so we’ll see how that holds together.
        Would you post the pics clarifying these points please?
      1. Eleventeen's Avatar
        Eleventeen -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        Would you post the pics clarifying these points please?
        Image 1: Valve cover suggests rear timing configuration
        Image 2: 4-bolt snout

        Attachment 58397
        Attachment 58396
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Eleventeen Click here to enlarge
        Image 2: Valve cover suggests rear timing configuration
        Anyone want to give it a crack at confirming?
      1. Eleventeen's Avatar
        Eleventeen -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        Anyone want to give it a crack at confirming?
        Not sure why the attachments didn't work the first 3 times, but I think I have this internet thing figured out now. Click here to enlarge Checkout my previous post again.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Eleventeen Click here to enlarge
        Not sure why the attachments didn't work the first 3 times, but I think I have this internet thing figured out now. Click here to enlarge Checkout my previous post again.
        They show, it works.

        Let's blow this part of the pic up a bit:

        Click here to enlarge
      1. Eleventeen's Avatar
        Eleventeen -
        Actually, now that you've cropped in on that photo, it doesn't look like it has the exhaust manifold integrated into the head. It looks like the runners are just super short. You can see the rear turbo with 3 individual inlets at the right of of the photo.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Eleventeen Click here to enlarge
        Actually, now that you've cropped in on that photo, it doesn't look like it has the exhaust manifold integrated into the head. It looks like the runners are just super short. You can see the rear turbo with 3 individual inlets at the right of of the photo.
        That's what I see too.