Injector timing

[James Ballenger]

    Vaporization is your friend.  It serves to cool the intake valve and
mixes superbly with the incoming air, leading to smaller fuel droplet sizes
than with current injectors and current pressures.  Most oem's strive to do
just the opposite of what you propose, they strive to time the injection
event while the valve is closed.  Obviously this only works up to a
particular duty cycle, depending on the fuel delivery range of the injectors
vs the engines fuel demand.

    Even if you wanted to get large  injectors such that at full duty cycle,
you would only be firing at a closed intake valve you would run into
problems.  Your top end power may increase incrementally, as well as your
top end emissions.  However, your idle quality would turn into a flaming
pile of dog crap.  You would have to use injection times that are too low
for accurate fuel delivery.  The two injector idea would work perfectly, but
I don't feel the added cost and complexity are even close to worth the
incremental gains obtainable.  Though it might be a consideration with
forced induction and very wide fuel range needs that prevent injector sizing
for the high end and low end.

My $.02,
James Ballenger


----- Original Message -----
From: "Rausch, Bernd" <br at rnt.de>
To: <diy_efi at diy-efi.org>
Sent: Tuesday, March 12, 2002 10:35 AM
Subject: Injector timing


> After thinking about injector sizes and timing I came up with the
following idea:
>
> When driving WOT at injector duties of 80-90%, you inject about 50-70% of
the fuel on the back of the closed intake valve. Due to the heat of the
valve, the fuel will vaporize. When the valve is opening, the first gas
entering the engine will be almost pure fuel, the air entering the engine at
later time contains much less fuel. So the fuel distribution is very uneven
and the you will get less air in the cylinder due to the vaporized fuel.
>
> What about using big injectors and injecting only when the intake valve is
open ? With opening times of about 230deg, you need big injectors with low
duty cycles of 720deg/230deg, about 30% at WOT.
>
> Did anyone try if the use of such big injectors with accurate timing will
improve power/fuel consumption ? I am aware that you will need a dual
injector setup to get the engine idle properly.
>
> Best regards,
> Bernd
>
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