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  1. #1
    Hugo
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    Does this supercharger capacity calc make sense?

    An Eaton M45 pumps 750cc per revolution.
    My 1800cc BMW m42 engine displaces 900cc per revolution.
    To feed the engine at 0.5 bar boost (1.5 bar absolute) the supercharger should turn 1.5 x 900 / 750 = 1.8 times engine RPM.
    Is that correct?


    Thanks,

    Hugo


  2. #2
    John N
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    Yup! That's the magic number. A more involved

    but essentially the same calculation is here:

    http://mg-tabc.org/supercharger/sc-harry-pyle.htm


    Regards,

    John N

  3. #3
    Shane williams
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    Re: Does this supercharger capacity calc make sense?

    Aup m8 i see you have a supercharger on your bimmer. Dont surpose you have an idea how to install it to my 318 m43 engine or atleast if you could tell us where about it should be fitted on the engine?

  4. #4
    Hugo
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    Why do you suppose I won\'t tell you? It\'s a forum!

    Don't be afraid to ask, that's what this forum is about! Now I'm not too familiar with the E36 318iS (M43 engine) because despite the fact that the M42 and M43 engines are pretty much the same, the cars are not. But anyway, here's the idea:
    I take away the big air-filter box and fix the supercharger (Eaton M45) on a bracket on the left inner wing. With some DIY flanges I fit the original TB and AFM to the inlet of the blower, and the outlet of the blower to the manifold. If you want, you can plumb in a by-pass valve for economy. The blower is driven with a multi-V belt, an extra pulley was made onto the original front pulley. Because the engine moves compared to the body / blower, I fit a belt tentioner and re-used the rubber inlet elbow that was between the filterbox and the TB now between the blower and the inlet manifold. Do take care to re-route the sump ventilation. Because I only use low boost (it's a high CR engine!) I didn't change anything on the EFI or ignition system, I only added a rather crude 5th injector, see linked page.

    Just go for it. It's a lot of fun, both building and driving.....
    Best regards,

    Hugo

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