[Diy_efi] BMW/Siemens stratified direct injection, link

[Bernd Felsche]

On Monday 30 October 2006 23:04, d at davidhunt.net wrote:
> I'm curious.

We agree on that, for sure! :-)

But please explain why you included the entire previous article when
you don't appear to refer to any of it?

> 1) If the fuel is delivered to the back of the intake valve and allowed
> to heat - is the 'atomization' required?  I realize that a larger O2
> charge is available if the fuel evaporates in the chamber, but what if
> full evaporation is the actual requirement?

That's not direct injection. Direct injection is directly into the
cylinder.  There is no valve between the injector and the combustion
chamber.

All the latent heat of evaporation absorbed by the fuel is then from
the gases being compressed in the combustion chamber. It provides
less time for evaporation so the droplet size has to be smaller.

There is no need to allow for "wetting" of inlet tracts and valves
with direct injection so the injected quantities can be far more
precise; resulting in greater power, fuel efficiency and better
control of emissions.

In terms of stratified charge, an ignitable rich "bubble" of
air-fuel mixture can be concentrated fairly reliably near the spark
gap; and allow the engine to run much "leaner" than a homogeneous
charge engine fed by port injection, TBI or fuel dripping from a
sponge into the inlet manifold.

Stratified charge is useful because the (Otto cycle) engine can
operate much more efficiently under light load conditions. That is
especially so when the throttle valve can be fully opened and the
power output regulated by mixture (and EGR flow) control.

> 2) If the fuel is evaporated at the intake valve, is there a serious
> problem mixing fuel with O2 in the chamber?

> ----- Original Message -----
> From: "Bernd Felsche" <bernie at innovative.iinet.net.au>
> To: <diy_efi at diy-efi.org>
> Sent: Wednesday, October 25, 2006 11:23 AM
> Subject: Re: [Diy_efi] BMW/Siemens stratified direct injection, link

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