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Date: Mon, 6 Jul 2009 17:08:09 -0600
From: Bob White <bob@bob-white.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Avoid reading .....
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On Mon, 6 Jul 2009 16:04:37 -0400
"Ed Anderson" <eanderson@carolina.rr.com> wrote:


<snip>
> Any time the EC2 is not grounding its' side of the injector (causing it
> to inject)  there is 12+ Volts at the EC2 injector pin on the EC2 box -
> Unless you have turned the disable switch for that pair of injectors
> off (no voltage to injectors). Until the EC2 grounding pulse there is
> no current flow and therefore no voltage drop across the injector.  So
> if there is 12+ volts on one side then there is 12+ volts on both sides
> including at the EC2 injector pin. Once the ground pulse is sent then
> the voltage is dropped across the injectors and there is indeed near
> zero volts on the EC2 pin. =20
>=20
> So I would think it would be easy for the EC2 to sense whether there is
> 12 volts on that pin between injector pulses and if there is 12+ volts,
> then the EC2 would know it is powered up.

Yes, that would work, so it's quite possible that the EC2 is keeping
track of which injectors have power.  I take back the blanket statement
that it isn't happening.  Sorry Steve.

<snip>
>=20
> Ok, we are now below staging point cooking along on two primary injectors=
 (I
> know you disagree with this point, Bob, but bear with me) When you drop
> below that staging point the EC2 automatically doubles the nominal pulse
> duration because you have stopped using the 2 secondary injectors.
> Normally you are using the two primary injectors below staging. So we sti=
ll
> have the same fuel flow below with 2 injectors that we had above staging
> point with 4 injectors =96 so fuel flow both sides of the staging point i=
s the
> same (ideally). Engine runs fine.
>=20
>=20
> Now, while below staging, you manually turn off the primary injectors by
> turning off their disable switch.  This removes power from the primary
> injectors and grounds the cold start circuit. But - wait, I postulate that
> below staging the cold start circuit is already in effect (doubling the
> pulse duration).  So there is no further doubling and the EC2 senses power
> removed from the primary injectors, senses power is still there on the
> secondary injectors and immediately starts firing the secondary injectors.
> Engine Runs Fine.
>=20
> NOW IF this theory is correct then turning on the cold start switch on the
> PCM panel with only one pair of injectors operating below staging - should
> do nothing regarding the pulse duration as its already double that that
> nominally required for 4 injectors. Engine Runs Fine.=20
>=20
<snip>

OK, but Steve has already reported that if he turns on the cold start
switch while at idle, the engine will run rich and die.  I'm pretty
sure I've done the same thing.  If one set of injectors is turned
off, then the engine will run fine.  I think the cold start doubling
and the staging pulse modification (halving on the way up and doubling
on the way down) are independent from each other.  At least I think I
understand our differences and thats some progress.  :)  I've always
assumed that the cold start switch on the PCM would always double fuel
flow and  setting cold start when disabling a bank of injectors would
always keep fuel flow the same (within limits).

Bob W.


--=20
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