[Diy_efi] Spark

[Bill Washington]

Gents,
The energy required to make the spark jump the plug gap is proportional to the
  (probably absolute) pressure in the cylinder at the time and probably inversely
  proportional to the degree of ionisation - along with other factors....

IE a 'weak' - (read damaged - shorted turns) coil may throw a spark across the 
plug gap with the plug sitting on top of the engine - but screw it in and no 
spark ..... It happened to me ...... and took quite a while (an hour or so) to 
identify the problem ... I had fuel and "appeared" to have spark but the engine 
would not start! new coil and 'hey presto' immediate action!

Regards
Bill

> Message: 2
> Date: Tue, 4 Oct 2005 12:10:42 -0400
> From: "John Gross" <jogross3 at hotmail.com>
> Subject: RE: [Diy_efi] The Hunt effect
> To: <diy_efi at diy-efi.org>
> Message-ID: <BAY103-DAV14BEF6317CBCCFCE428AD383830 at phx.gbl>
> Content-Type: text/plain; charset="us-ascii"
> 
> It takes more energy to cause the fuel to "flash" without a specific
> ignition point.  The spark from the plug on your car is more than enough to
> start the burn on just about any unleaded fuel.  I say unleaded to try to
> keep the discussion within reason in terms of octane ratings and appropriate
> CRs for the engines.  It takes more spark energy to light off a 115 octane
> fuel than it does an 87.  However, when talking about street-driven cars,
> any delay in the formation of the kernel (the initial point of combustion
> inside the spark plug gap) is so minute, that it is not worth considering.
> Additionally, what makes it harder and harder to light the air-fuel mixture
> isn't just the fuel, but the dynamic compression.  That's why blower motors
> typically need a more robust and powerful ignition system..the turbulence
> inside the cylinder in a blown motor (high dynamic compression) can actually
> extinguish the kernel, thus stopping combustion.  
>