[Diy_efi] injecting 5 port head

[Carter Shore]

On 2006-12-26 Daniel Nicoson wrote:

> Here's a stupid question, Does it actually have to
> be sequential?  We tend
> to focus on sequential since most autos use that but
> the OEM went to
> sequential primarily for emissions reasons at low
> RPM.
> 
> What if you thought more along batch-fire lines. 
> Put your injectors back up
> in the intake runner a few inches (no machining on
> the head itself this way)
> and then fire all the injectors every time an intake
> valve opens for 1/4 the
> PW (on 4-cylinder).  Not claiming to have it all
> worked out but trying to
> keep minds open.  Batch fire systems have worked
> great for a long time,
> especially at other than idle RPM.
> 
> These engines probably won't know the difference
> between fuel injection or
> carburetion as long as they get the fuel they need.
> 

Using TBI would be a lot simpler, but there are still
issues. Ideally, the intake manifold would be filled
with a homogeneous air/fuel mixture, as in a properly
set up carb system. The issues of timing, etc. would
go away.
But since EFI controls mixture by duty cycle, even
with TBI, there will be regions of rich and lean
inside the manifold.
One solution is to deliberately introduce turbulence,
but that will work against VE at WOT.
Another scheme is to increase the pulse frequency, so
that each intake charge to a given cylinder will
consist of many small injection events instead of a
few larger ones.

Another issue to consider with the Spitfire dual carb
manifold and TBI is that the 'balance tube' between
the main intake runners actually draws charge accross
from both carbs (throttle bodies) during intake
events. So attempts to synchronize the injection
events may need to consider that flow.

I've also considered putting the injectors into the
head, rather than the manifold. This is do-able on a
Spitfire, not sure about a BMC-A.

Carter

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