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Engine displacement after rebuild question

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  • MileHighM3
    replied
    Originally posted by M3 Adjuster View Post
    a mild overbore of .020 over and I believe .040 is acceptable in BMW CCA club racing , and one can still stay in the same class.... so I am sure that this is a negligible increase in displacement otherwise everyone would be boring their engines blocks for more power.
    That's probably the case... I doubt they did anything too major that would have bumped them out of their class. I could hope though!

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  • M3 Adjuster
    replied
    a mild overbore of .020 over and I believe .040 is acceptable in BMW CCA club racing , and one can still stay in the same class.... so I am sure that this is a negligible increase in displacement otherwise everyone would be boring their engines blocks for more power.

    Leave a comment:


  • Ted B
    replied
    Originally posted by MileHighM3 View Post
    I'll cross my fingers and hope they too more than that when they were in there!
    I think you may have the wrong idea. Increasing the displacement from let's say 2.3L to 2.5L involves a completely different crankshaft and pistons, and is not done by simply boring the block.

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  • ShiftBMW
    replied
    Take it in and dyno it. Then you'll have a legit idea instead of speculating.

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  • MileHighM3
    replied
    I'll cross my fingers and hope they too more than that when they were in there!

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  • Ted B
    replied
    A standard 0.030" overbore will give an extra 38cc, or a little over a 1% increase in displacement, which is insignificant. Most engines clean up at 0.020", so that's even less of a change.

    I have no idea of what the engine makes as far as power, but with the ambient pressure in Denver at only ~12.1 psi, it's going to be about 17% down in power as opposed to sea level. You're probably close to where a stock M3 would be at sea level.

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  • MileHighM3
    started a topic Engine displacement after rebuild question

    Engine displacement after rebuild question

    From what Bimmer Haus told me can you guys help me figure out what my displacement might be? They told me that it had it's 1st "Stage" (if that's the right word) bore on it for the engines first rebuild. .2 liters is almost nothing but if they just bored it out to smooth out the walls would that make that much of a difference in the displacement? Also, from what I can tell, i have the foam seal on the airbox which means it should have the Evo air box and it does have the K&N. Also I haven't hit the rev limiter on it yet and took it to 8k rpm's... so it's probably chipped too. Racing dynamics header and 3 inch exhaust with no cat. What do you think this engine is pushing as far as HP? I really need to get a hold of them to find out everything that's been done to this car. Thanks in advance... I'm still learning.
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