As I understand it, the = injectors=20 are staged. The secondaries only cut in at a certain rpm. So, if = you're rpm is=20 below the staging point, and you kill the primaries you have no fuel = and=20 engine will quit. Above the staging point the secondaries would be = supplying=20 fuel. Just a theory, but it makes sense to = me...

Regards,

John

I was = thinking that=20 Tracy took this = into=20 account, but after reading the instructions again, it does look like = he just=20 depends on the cold start function to add fuel. I guess you = won=92t be=20 using any power setting below the secondary staging point during = normal=20 flight, except for maybe a steep descent.

Of course I = have to=20 wonder, why not just run them all, all the time? Mazda probably = made=20 them staged for emissions, or drivability, but there are FD guys = running four=20 1600 injectors, who seem to idle just fine with two 1600 = injectors. =20 Surely I can idle with four 550=92s. I think the staging point = is=20 adjustable, but I=92ll have to look at the manual again = tomorrow. I might=20 just be tempted to try running all four full time. =

Rusty

Rusty, I = think you=20 would find that you would have too much fuel in the intake at low = rpms. =20 That is the primary reason that the EFI's have staged injectors. = The=20 larger the flow rate of the injectors, the worst the problem = becomes at=20 idle. It gets to the point where the injectors would have to = react to=20 sub millisecond pulses to dispense the small amount of fuel needed for = idle,=20 just cheaper to stage than try to develop injectors that = responsive. The=20 low flow limit on MOST EFI fuel injectors is around = 1-2milliseconds. If=20 the pulse is less than that the injector simply can not open and close = responsive enough.

If you set = it up as=20 Tracy recommends, you can run the engine on either pair of injectors = at any=20 engine regime from idle to WOT. Now at WOT with only one pair = you may=20 not get quite as much power as when using only two injectors they will = reach=20 satuation (simple stay open and don't close) at some rpm/power = point. =20 Then, of course, no additional fuel will flow. I haven't = calculated what=20 that point is and its further up the rpm range for the larger flow=20 injectors. But, I can tell you a rotary powered RV has no = problem=20 staying airborn with only two 460cc/min injectors working. My = engine=20 seems limited to around 5800-5900 rpm with only two inejctors and can = get up=20 to around 6100-6200 with all four pumping fuel.

FWIW

Ed=20 Anderson