[Diy_efi] injecting 5 port head

[Adam Wade]

--- Jean Belanger <jean at jeanbelanger.net> wrote:

> If you only inject when the intake valves are open
> then the fuel will be carried to the right cylinder.

I think you are forgetting that the intake openings of
the cylinders sharing the siamesed port overlap each
other, so unfortunately it's not nearly as simple as
you appear to be claiming.  You might be able to
manage with a single injector, but I would wager it
would be easier to implement with multiple injectors. 
In particular, as I understand it, you cannot inject
fuel prior to the closing of the "inside" cylinder's
intake valve and have any of that fuel end up in the
"outside" cylinder -- for cylinders 2 and 3, you are
limited to the time between the closing of the #2/3
intake valve and the closing of the #1/4 intake valve,
which is a pretty short period, especially at higher
rpms.  In fact, you posted the link to the info on
this just the other day!  His site has been moved,
though. 
<http://www.shell-4000-rally.org/starchak/efi/siamese.htm>

I think a staged injector system might be in order
here; in fact, it's possible that the optimal
combination would be a single sat. drive injector for
cylinders 2 and 3 (since you can inject fuel starting
when the "outer" cylinder closes its intake valve, you
have a decent amount of time to allow injection of
sufficient fuel volume before the "inner" cylinder
opens its intake valve, even with a smallish sat.
drive injector), and staged dual injectors for
cylinders 1 and 4, which would allow a honkin' big
injector for higher-load running and a small injector
to handle idle control.  Timing the injection on the
center pair of cylinders will be critical.

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