[Diy_efi] timeframe to get equal fuel distribution

[Adam Wade]

--- joeld <joeld at ualberta.ca> wrote:

> I have got some 670gram/min injectors that have a 60
> degree cone pattern.  We are planning on using them
> to inject directly into the cylinder of a two-
> stroke.

This sounds like a spectacularly bad idea to me. 
Aside from the fact that port injectors will melt,
they will also carbon over, and are not designed for
the injection pressures you will need.

I just read through the entire multimedia presentation
from Bosch on their 4-stroke GDI system, and direct
injection is a whole different animal, including every
part of injector design.  They use an internal
diffuser disk setup inside the injector to produce
fuel spray that is much wider in patters, with much
smaller droplet size, and operating in far higher
injection pressures.

One of the things they mention with stratified charge
in particular was that they HAD to alter fuel pressure
to change the atomization characteristics and spray
distance from the injector, since any fuel that made
it to the piston top would just wet the piston, and
while it would eventually evaporate, it wuld defeat
most of the reason for bothering with GDI at all
(reduced emissions and reduced fuel consumption).

> What I was wondering from everyone is if they had 
> any input as to how much time needs to be allowed
> for the fuel to adequately  mix with the air.

For GDI uses, I doubt you could ever get fuel injected
with a standard port injector into the cylinder to
vaporize in a reasonable amount of time, and certainly
not to any real advantage over port injection.

check out what Orbital is doing with Aprilia.  Their
system is farily different from Bosch's 4-stroke
system, but allows a lot more latitude in injectionj
time, because it has a separate chamber for the rich
mixture, which is released into the spark plug area
RIGHT before ignition.  This again negates some of the
emissions and consumption benefits of GDI, but is a
lot better than a conventional two-stroke, and might
be "good enough" for what you want to do.

=====
| Adam Wade                       1990 Kwak Zephyr 550 (Daphne) |
|   http://y42.photos.yahoo.com/bc/espresso_doppio/lst?.dir=/   |
| "It was like an emergency ward after a great catastrophe; it  |
|   didn't matter what race or class the victims belonged to.   |
|  They were all given the same miracle drug, which was coffee. |
|   The catastrophe in this case, of course, was that the sun   |
|     had come up again."                    -Kurt Vonnegut     |

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