As I understand it, the injectors
are staged. The secondaries only cut in at a certain rpm. So, if you're rpm is
below the staging point, and you kill the primaries you have no fuel and
engine will quit. Above the staging point the secondaries would be supplying
fuel. Just a theory, but it makes sense to me...
I was thinking that
Tracy took this into
account, but after reading the instructions again, it does look like he just
depends on the cold start function to add fuel. I guess you won’t be
using any power setting below the secondary staging point during normal
flight, except for maybe a steep descent.
Of course I have to
wonder, why not just run them all, all the time? Mazda probably made
them staged for emissions, or drivability, but there are FD guys running four
1600 injectors, who seem to idle just fine with two 1600 injectors.
Surely I can idle with four 550’s. I think the staging point is
adjustable, but I’ll have to look at the manual again tomorrow. I might
just be tempted to try running all four full time.
Rusty
Rusty, I think you
would find that you would have too much fuel in the intake at low rpms.
That is the primary reason that the EFI's have staged injectors. The
larger the flow rate of the injectors, the worst the problem becomes at
idle. It gets to the point where the injectors would have to react to
sub millisecond pulses to dispense the small amount of fuel needed for idle,
just cheaper to stage than try to develop injectors that responsive. The
low flow limit on MOST EFI fuel injectors is around 1-2milliseconds. If
the pulse is less than that the injector simply can not open and close
responsive enough.
If you set it up as
Tracy recommends, you can run the engine on either pair of injectors at any
engine regime from idle to WOT. Now at WOT with only one pair you may
not get quite as much power as when using only two injectors they will reach
satuation (simple stay open and don't close) at some rpm/power point.
Then, of course, no additional fuel will flow. I haven't calculated what
that point is and its further up the rpm range for the larger flow
injectors. But, I can tell you a rotary powered RV has no problem
staying airborn with only two 460cc/min injectors working. My engine
seems limited to around 5800-5900 rpm with only two inejctors and can get up
to around 6100-6200 with all four pumping fuel.
FWIW
Ed
Anderson