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    • BMW sandbagging the F10 M5? 22 psi vs. 17 psi of boost for the S63tu compared to the X5 and X6 M S63 + higher compression ratio and VALVETRONIC

      BMW provided a press release today with some new details on the F10 M5. Included in these details were that the boost is higher at 22 psi in the S63tu (F10 M5 motor) vs. 17.4 psi in the standard S63 V8 twin turbo in the X5 and X6 M. The compression ratio is also at 10.0:1 the same as the N63. The X5 and X6 M as you remember from our twin turbo V8 comparison article have 9.3:1 compression ratios. So the F10 M5 is higher compression and higher boost yet only rated 5 horsepower higher with rear wheel drive?

      The compression ratio was not included in the press release but we e-mailed BMWNA and did receive confirmation the F10 M5 will have a 10.0:1 compression ratio. Will the pistons be the same as those in the N63? Certainly an interesting question.

      The other interesting development is that the F10 M5 S63tu will have VALVETRONIC which BMW claims effectively gives the motor 16 individual throttles. VALVETRONIC being a variable valve control system. The ECU controls engine power directly by varying lift of the intake valves. This system minimizes losses which of course provides a MPG as well as torque boost. The claim is also that it will sharpen throttle response.

      Is this car putting out more than just 5 horsepower more than the X5 and X6 M? We think so.


      This article was originally published in forum thread: BMW sandbagging the F10 M5? 22 psi vs. 17 psi of boost compared to the X5 and X6 M + higher compression ratio and valvetronic started by Sticky View original post
      Comments 63 Comments
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by 654 Click here to enlarge
        M5 gets special lightweight parts compared to 550i. However, the power is disappointing.
        The power is disappointing? How so?
      1. Sorena's Avatar
        Sorena -
        OK, one thing bothers me here. Does this 22psi pressure include atmosphere pressure? or it's just "boost"?
      1. inlineS54B32's Avatar
        inlineS54B32 -
        Click here to enlarge Originally Posted by Jimefam Click here to enlarge
        Have you seen the picture of the S63 disassembled? I wouldnt exactly describe the rods as "beefy" lol still probably good for 800hp at least. BMW jacks up the price on their stuff enough that you could probably get a custom set from Carrillo for about the same cost.
        The S63tu comes with different con rods than the S63. Are the S63 rods weak because of material or size? Curious why they are considered to be weak (S63 or S63tu)
      1. inlineS54B32's Avatar
        inlineS54B32 -
        Click here to enlarge Originally Posted by Sorena Click here to enlarge
        OK, one thing bothers me here. Does this 22psi pressure include atmosphere pressure? or it's just "boost"?
        Just boost (absolute) - which is nuts: 1.5 bar is 21.75 psi ... Grabbed this from the press release:
        Maximum Boost Pressure (absolute) 1.5 bar (s63tu) 1.2 bar (s63)
      1. Sorena's Avatar
        Sorena -
        Thanks. Then this means this 22psi boost appears at very low rpm's and then decreases. Wondering if BMW did this to improve the torque curve or it's just the turbos that go out of breath in higher rpm's.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by inlineS54B32 Click here to enlarge
        The S63tu comes with different con rods than the S63. Are the S63 rods weak because of material or size? Curious why they are considered to be weak (S63 or S63tu)
        How do you know the S63tu conrods are different?
      1. inlineS54B32's Avatar
        inlineS54B32 -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        How do you know the S63tu conrods are different?
        I read it somewhere, but cannot find up a verifiable link besides a post on a forum.

        If they crowned the piston, displacement would decrease. If they shaved the head, same thing. It's the only thing that makes sense to me if two engines of the exact same displacement have two different static compression ratios. Could be wrong.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by inlineS54B32 Click here to enlarge
        I read it somewhere, but cannot find up a verifiable link besides a post on a forum.

        If they crowned the piston, displacement would decrease. If they shaved the head, same thing. It's the only thing that makes sense to me if two engines of the exact same displacement have two different static compression ratios. Could be wrong.
        I never saw anything regarding the rods, these are the differences I know: http://www.bimmerboost.com/showthrea...nd-valvetronic
      1. inlineS54B32's Avatar
        inlineS54B32 -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        I never saw anything regarding the rods, these are the differences I know: http://www.bimmerboost.com/showthrea...nd-valvetronic
        Looks like I might have been wrong - but am still wondering how the displacement stayed the same: http://www.bmwblog.com/2011/09/22/bm...-of-the-beast/
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by inlineS54B32 Click here to enlarge
        Looks like I might have been wrong - but am still wondering how the displacement stayed the same: http://www.bmwblog.com/2011/09/22/bm...-of-the-beast/
        Isn't the bore and stroke the same?
      1. inlineS54B32's Avatar
        inlineS54B32 -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        Isn't the bore and stroke the same?
        Right - it is. Looks like only the crown changed then?
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by inlineS54B32 Click here to enlarge
        Right - it is. Looks like only the crown changed then?
        I'm looking at all differences and the heads obviously due to valvetronic and the pistons. I do not know what else? Oh, the turbos are different and the manifold is more efficient as well I believe.
      1. inlineS54B32's Avatar
        inlineS54B32 -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        I'm looking at all differences and the heads obviously due to valvetronic and the pistons. I do not know what else? Oh, the turbos are different and the manifold is more efficient as well I believe.
        Yeah, this looks right. I am killing myself trying to find this post (who knows if it is real) that says they (s63 and tu) do not share the same rods... Again, could be wrong. Click here to enlarge

        I am still not understanding this though, and would love for a mech-e to chime in on this. If displacement is the same, wouldn't adding a crown change this displacement? I guess I am just not sure if changing the "advertised" displacement changes the actual.

        I honestly am confused at this point, not sure... Click here to enlarge
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by inlineS54B32 Click here to enlarge
        Yeah, this looks right. I am killing myself trying to find this post (who knows if it is real) that says they (s63 and tu) do not share the same rods... Again, could be wrong. Click here to enlarge

        I am still not understanding this though, and would love for a mech-e to chime in on this. If displacement is the same, wouldn't adding a crown change this displacement? I guess I am just not sure if changing the "advertised" displacement changes the actual.

        I honestly am confused at this point, not sure... Click here to enlarge
        Ask one of the engine builders, @activ3 @A4RingedONE8T @Mike@VAC
      1. inlineS54B32's Avatar
        inlineS54B32 -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        Ask one of the engine builders, @activ3 @A4RingedONE8T @Mike@VAC
        Thanks - that's appreciated.

        The above should read: If boreXstroke is the same, wouldn't adding a crown change the displacement?
      1. Sorena's Avatar
        Sorena -
        No, that only effects the CR i believe.
      1. Jimefam's Avatar
        Jimefam -
        Yes it should change but I'd imagine the difference would be minimal. I saw a good drop in CR when we cut valve reliefs into a set of pistons but I'd guess the change in displacement was inconsequential.
      1. A4RingedONE8T's Avatar
        A4RingedONE8T -
        Didn't read the whole thread but yes of course adding a dome, crown, valve relief, etc. to a piston will change the displacement, but you're talking about very minimal CC's, if I had to guess somewhere between 10-20, practically negligible, especially when referencing a boosted motor. Altering the top of the piston can have some noticeable affects though, not including displacement change, but proneness to knock, spark blow out, etc. Just because you can machine a piston doesn't mean you understand the movement of the combustion inside the specific chamber of that application
      1. dreikraft's Avatar
        dreikraft -
        its starting to grow on me. but like others have mentioned... how to fit bigger snails?
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by A4RingedONE8T Click here to enlarge
        Didn't read the whole thread but yes of course adding a dome, crown, valve relief, etc. to a piston will change the displacement, but you're talking about very minimal CC's, if I had to guess somewhere between 10-20, practically negligible, especially when referencing a boosted motor. Altering the top of the piston can have some noticeable affects though, not including displacement change, but proneness to knock, spark blow out, etc. Just because you can machine a piston doesn't mean you understand the movement of the combustion inside the specific chamber of that application
        Thanks, so basically the displacement amount changed is practically irrelevant.