[Diy_efi] Re: Diy_efi Digest, Vol 4, Issue 20

[Bill Washington]

Mike, Adam,
Gentlemen, gentlemen, gentlemen!
Please be nice...
I drive a car with an old technology (Bosch mechanical injection) 
'indirect' injection diesel engine - let me explain the construction of 
the cylinder head and piston - the top of the Piston is essentially 
flat, as is the head, and at top dead centre they would impact each 
other except for the thickness of the head gasket! set into the head is 
a blind spherical void with a very small entry hole, in this void are 
mounted the glow plug and the injector.
    This system works on the basis that the expanding combustion product 
gases within the spherical chamber are sufficiently evacuated in the 
power and exhaust stroke that the following induction and compression 
strokes force enough of the new charge into the chamber for the next 
injection of fuel to have enough oxygen to burn.

    Now while I acknowledge that the ICE engines being discussed achieve 
less than half the compression of the diesel, and the volume of the 
'greenfire' plug is somewhat smaller than the spherical chamber in the 
diesel it is clear to me that by the same process sufficient combustible 
gas mixture will be forced into the plug to initiate the combustion 
process at the next spark event - the fact that it does work confirms this.

    I will not get into any discussions about how well it may or may not 
work, or the effect on the required ignition timing - I like many of you 
remain 'a little' skeptical on the claimed benefits --- but hey who 
knows....I await empirical evidence on its efficacy....

    On the glow plugs that were mentioned by Ernest Bucler It sounds to 
also be an interesting concept with the limitations he has espoused - 
model plane engines have been running with glow plugs for many years, 
but perhaps these are more suited to constant power/constant rpm 
engines.....rather than automotive applications - except perhaps in 
hybrid vehicles.....

Regards
Bill

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