[Diy_efi] injecting 5 port head

[Carter Shore]

On 12/26/2005 Jean Belanger wrote:

> The problem with the way you want to do this is that
> you need injectors that
> flow enough fuel at < 25% duty cycle and not 50%. So
> your idle problem is
> even worse that you thought.

Yah, that's true. One way to extend the dynamic range
of the injectors at low RPM is to put fuel pressure
under ECU control; the Ford return-less setup uses a
fuel pressure sensor and PWM to the fuel pump, so this
is do-able.

> You don't really need to have 2 injectors per port.
> If you only inject when
> the intake valves are open then the fuel will be
> carried to the right
> cylinder. This will simplify packaging and injector
> selection, and help
> idle. The scheduling algorithm will then be required
> to inject for each
> injector in a sequence such as pulse, pulse, wait,
> wait.

I'm still up for 4 injectors, if only to preserve the
option of tweaking 'per cylinder' as needed. I'm not
subject to 'bean counter' constraints like the factory
engineers. And I also don't need to worry about CAFE
and other regulatory issues.

> I agree about the variable timing aspect. I'm
> planning to time the injection
> pulse with respect to the middle of the pulse and to
> have a timing table
> that varies timing with respect to RPM and load
> (either MAP or TPS).
> 
> By the way, are you designing your own ECU or are
> you using an available
> one?

The control hardware will be custom, and I have not
settled on a platform yet. I'm considering a
distributed architecture, where semi-independent nodes
manage fuel and ignition on a 'per-cylinder' basis. A
central node sends out high level status/commands, and
serves as a collaboration node on common issues
through a shared communication network. 

This gives me a lot of freedom in platform selection,
as the timing and control issues relate to just one
task, and autonomous operation is possible for
'limp-home' mode.

By defining the ECU as an architectural interface and
functional responsibilities, I can implement any node
with the appropriate hardware/software to do the job,
and change those out with newer/better ones as needed
without throwing away the whole thing and starting
over. 

Carter Shore



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