REFLECTOR: The definitive answer on octane and av-gas

[Jim Sower]

I only heard that the ignition technology back in the 20s (that would be 
mags which haven't changed appreciably since then) would not support 
long distance flight.  With two systems, you could limp to your 
destination when (note "if" was never at issue) one system failed.
Most of the rest was someone trying to start a good rumor IMO ... Jim S.

dandemitchell at earthlink.net wrote:

>What ever happened to this thread? I have nothing past this date.
>
>As I was informed during flight school, the reason for the dual ignition,
>other than safety, was it could handle a multitude of octane fuels. The
>reason was that the flame front is originating from two different positions
>and thus the total time to burn the fuel was reduced. I was told the longer
>burn time of a single plug cylinder could lead to higher combustion chamber
>pressures thus causing pre-ignition where the flame had not yet reached.
>The dual plug design allowed later firing, less kick-back (fixed firing
>point), and quicker fuel burning. This reduced the cylinder pressures
>during the burn cycle and thus the potential of pre-ignition at high power
>settings. Note I did not talk about chemistry etc., I know nothing there
>except to keep di-hydrogon monoxide out of the fuel/oil. (if that is that
>is the correct formula)
>
>Ed Mitchell
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>>[Original Message]
>>From: John Dibble <aminetech at bluefrog.com>
>>To: <Jim_Agnew_2 at yahoo.com>; Velocity Aircraft Owners and Builders list
>>    
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><reflector at tvbf.org>
>  
>
>>Date: 2/13/2005 9:55:52 AM
>>Subject: Re: REFLECTOR: The definitive answer on octane and av-gas
>>
>>My understanding is that the dual ignition did not compromise power. 
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>Another,
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>>simplier solution which I used was to remove the cylinders and add 2
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>additional base
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>>gaskets which lowered the compression ratio.  This did reduce power which
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>was only
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>>noticeable during rapid acceleration.  Again, the benefit of dual
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>ignition for
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>>mototcycles, may not apply to aircraft engine, but I would like to
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>explore it.
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>>John
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>>Jim Agnew wrote:
>>
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>>>I suspect that the dual ignition allowed for a retarded spark timing to
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>allow
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>>>for the lower octane fuel.  It will work up to a point, however the
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>engine will
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>>>produce less power.
>>>
>>>      
>>>
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