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Combustion times and related info

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  • ray_r.rm
    Group: I am interested in the times associated with combustion and the best crank angle when peak pressure occurs. Since NASCAR engines turn 9000+ rpm and make
    Message 1 of 46 , Nov 2, 2006
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      Group:
      I am interested in the times associated with combustion and the best
      crank angle when peak pressure occurs.
      Since NASCAR engines turn 9000+ rpm and make best power there, it
      seems that the "burn time" must be short. What does the high rpm bike
      community think is the best time to initiate the spark? Anyone know
      what the NASCAR engine uses for timing?

      After the fuel is ignited somewhere before TDC, the pressure builds up
      as a result of the piston ascending and the burning taking place.

      Is it best to have the peak pressure occur at TDC or somewhat after,
      where the rod angle to the crank is better?

      I realize this is a very nebulous area, but do you have any guidance?

      -- Rich
    • Ian
      ... I disagree, there are many examples of inexperienced / tired / stressed pilots crashing planes due to wrong mixture settings. I would suggest that many
      Message 46 of 46 , Nov 21, 2006
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        >Aircraft engines are basically constant speed, constant load devices.
        >Push it rich for takeoff, throttle back for cruise, lean for the
        >correct EGT drop, and you're done for the duration. Other than maybe
        >breaking a mixture control cable, there's nothing to screw up.


        I disagree, there are many examples of inexperienced / tired /
        stressed pilots crashing planes due to wrong mixture settings.
        I would suggest that many more are killed by having the
        "choice", than ever would be by failed electronics ( With
        suitable backup, including dual alternators & 2 smaller
        batteries )


        >Magnetos are simpler than a belt/alternator/distributor setup, and
        >you'd have to have some kind of distributor drive anyway,


        Electronic ignitions don't.


        >Reliability was the major idea with all of this. You don't just pull
        >over to the side of the air and open the cowl if something quits. And
        >there are lots of places - water, forest - that you can't land.


        Yep, I've heard all these arguments. Using this line of argument, how
        then do you justify using OHV engines in the first place, side-valve
        engines work perfectly well, have only 1/3 the moving parts in the
        valve train, are physically smaller and lighter.


        >Multiple-redundant electronics would be okay, but there are darned few
        >light aircraft that have been designed since the invention of the
        >microprocessor, and in the USA that means getting FAA certification,
        >which is a hassle, and product liability insurance, which could be
        >prohibitive.


        At least I agree totally with this paragraph.


        Cheers IAN


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