Fuel Atomisation

[Bob - Uni]

Hello Greg,

Is that why bigger injectors that flow higher but dont atomise as well
tend to rob you of idle quality and low down power? Would it be better
then to have two smaller injectors per cylinder than one bigger one?

Monday, December 10, 2001, 7:22:30 AM, you wrote:

GH> The carby (talking IR carbys, one throat per cylinder, such as Weber DCOE;s
GH> or IDA's with the butterflies fairly close to the intake valves) puts
GH> finely atomized fuel into the high velocity airstream (and no fuel flow
GH> when there is no air flow) in the intake port. Most of the atomized fuel
GH> makes it into the cylinder without vaporizing. Of course, SOME of the fuel
GH> gets vaporized before the intake valve closes, but not all that high a
GH> percentage of it. (Which comes under the heading of nothing is perfect.)

GH> Most port EFI designs deliberately injects the fuel onto the back side of
GH> the _closed_ intake valves (or somewhere in that vicinity, if they are
GH> lucky) at a point in time when there is little, if any, air velocity in the
GH> port. This is done so that the heat in the valve, combined with the
GH> reversion of exhaust gas into the intake during overlap will _vaporize_ the
GH> fuel, and thus _compensate_ for the (conventional) port injector's
GH> inability to atomize it very well at all.

GH> The heat that is taken from the intake valve to vaporize the fuel is robbed
GH> from the next cycle. Thus the deterioration in thermal efficiency. The
GH> vaporized fuel displaces a great deal more O2 in the inlet charge than
GH> atomized liquid fuel does--thus the deterioration in volumetric efficiency.

GH> My own pet theory is that it would take air shrouded port fuel (and water,
GH> SHHHH!!) injectors, injecting their (respective) highly atomized fluids in
GH> time with high velocity air flow in the inlet ports, probably in a
GH> direction retro to the flow in the port, in order to get to the level of
GH> mixture and burn "quality" that good carbys can give.

GH> Hope that helps.

GH> Greg
>>
>>___
>>
>>Arnaud


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-- 
Best regards,
 Bob                            mailto:rcs07 at uow.edu.au

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