Different CR side to side

Discussion in 'Engines' started by R Pope, Apr 20, 2013.

  1. R Pope

    R Pope Member

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    Anybody know why many V-type engines had different comp. ratios side to side? All the DB's seem to be that way. Even the Ford flathead! On the Ford engine it is caused by the cylinder Vee not being centered on the crankshaft centerline, Henry's way of getting the same effect as offset wrist pins used by most other manufacturers. The offset caused the in-block valves to enter the chambers at different angles, changing the volume of the combustion chamber. This would not be an issue with overhead valves/cams, so what other reason is there?
     
  2. tyrodtom

    tyrodtom Well-Known Member

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    The DB-601's supercharger outlet was on the left rear of the engine, so it delivered slightly more air to that bank of cylinders, so the left side combustion chambers had a little less compression to compensate.
     
  3. R Pope

    R Pope Member

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    I guess that makes sense, in a Teutonic sort of way. Any other engineers would have fixed the intake system.......
     
  4. Shortround6

    Shortround6 Well-Known Member

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    There is some dispute about that, Some people think it was an oil slinging problem. Junkers engines had off set superchargers and yet used the same compression ratio on both sides. Some Russian engines may have used different compression ratios on different banks. Some engines may have been different but the difference not enough to really talk about? A number of engines had different stokes on each bank (articulated rods) and even using different pistons it is hard to get exactly the same compression ratio.
     
  5. tyrodtom

    tyrodtom Well-Known Member

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    I can see how a inverted V engine might have a oil control problem on one side, because crank rotation would tend to sling oil down one bank of cylinders more than the other. But how does the compression ratio compensate for that ?
     
  6. Jugman

    Jugman Member

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    It dosn't. Oil in the cylinder reduces the knock value of the fuel. The lower c/r in the left bank is to compensate for this.
     
  7. tyrodtom

    tyrodtom Well-Known Member

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    OK, I can see that. That makes sense.
     
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