Bill,
I’ve inserted red comments below. They refer to what happens at MAP less
than the staging MAP. There is no
significance to the choice of red other than it shows up well.
Steve Boese
-----Original Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Bill Bradburry
Sent: Monday, July 13, 2009 9:41 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: cold
switch and injector backup mode
Bob, Steve,
My comments were really directed to the statement that
Steve made. First of all, he tested the cold start switch which is
designed to provide a richer mixture for starting in cold weather. It
pretty much has an effect only at low manifold pressure which you would see
while cranking. I don’t have any issue with those statements.
The statement that I think is not correct is the one
here:
“Turning off the power to either the primary or
secondary injectors has no effect on the pulse width
applied to the injectors or the status of the staging data bit.”
Tracy
pretty much states that turning off either of the
injectors will automatically turn on the cold start and double the pulse width
of the injectors. With my EC2,
turning on the cold switch does not change the pulse width. It forces the controller to use all four
injectors. That way, when a double
pole switch is used to turn off one set of injectors and simultaneously ground
the cold switch line, the other set of injectors will be used and the engine
will run normally if the injectors are all of similar flow rate. Since only one set is
getting power, that has the effect of making one set
produce like two sets. No, the
set still getting power produces the same amount of fuel as before. If the secondary injectors are turned
off, the operation of the primaries are unchanged and the amount of fuel going
to the engine is unchanged since the secondaries
weren’t producing fuel anyway.
If the primaries are turned off, the secondaries
now are producing the same amount of fuel that the primaries were. Now if Steve had the cold
start switch already turned on when he disabled the injectors in the statement
above, there would probably be no additional doubling. But I don’t
think we are supposed to do the disable test with the cold start switch on
because that is redundant since the cold start is turned on when you turn off
one set. At MAP below the staging threshold, turning on the cold
switch with all injectors receiving power doubles the fuel flow since all four
injectors are now being used instead of just the primaries. What happens with the cold switch on,
all injectors receiving power, and MAP above the staging threshold, probably
doesn’t matter much since hopefully the engine isn’t being warmed
up from a cold start at MAP above the staging threshold.
Also, I agree with you Bob about the smaller Renesis
injectors. I am switching to 4 yellow injectors on mine. By the
way, that means that I will have a couple of blue injectors for sale soon if
any one is interested.
Bill B
-----Original Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On Behalf Of Bob White
Sent: Monday, July 13, 2009 9:37 PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: cold switch and injector
backup mode
Hi Bill,
What you've posted below shown behind '>' :
> Below staging manifold pressure, cold start
doubles fuel flow by
> turning on both sets of injectors, effectively
canceling staging.
True, but I think this the right way to look at it is
that the staging bit cuts the pulse width in half at the same time the cold
start switch doubles it, so the net effect is that both sets of injectors are
being triggered with the same pulse width you started with (below staging).
> The injector disable does not work above the
staging point. If you
> kill one set above the staging manifold pressure,
you will just be
> running on one set at the normal pulse
width. This will result in
> only half power or less available anywhere above
the staging point manifold pressure.
Not true, mostly. If you've disabled one set of
injectors below staging, then the engine is receiving the correct amount of
fuel and it's effectively running as though it only has two injectors. As
power is increased, the pulse width increases until the injectors are flowing
the maximum amount of fuel possible. The total power will be limited to
that level, but not half. If two injectors will flow enough gas to run at
full power, then you will be able to produce full power.
You aren't running with the "normal" pulse
width above the original staging point. The staging point would have cut
the pulse width in half, but since the staging has effectively already taken
place, the pulse width is correct for above the old staging point also.
So, your assumption will be true only if you require
both sets of injectors to produce full power and they will only do so if
running at full capacity. Two 50# injectors will flow 100 lb/hr and at a
bsfc of .5 that will allow 200 hp, or at .6 bsfc, 166 hp.
In thinking about it this way, it seems to me to be a
bad idea to use the small RX-8 injectors for the primaries, because disabling
the secondaries would limit you to less than half power. Mazda does it
for better idle in the car, but not a big problem in aircraft use. Better
to use the same size injectors for primary and secondary and size them to
maintain enough power for level flight as a absolute minimum.
There's a problem even then as it's easy to push the
engine too lean with the throttle when the injectors max out. Same size
Pri and Sec also eliminates one adjustment in the EC2, and it has more than
enough adjustments as it is. :)
Bob W.
On Mon, 13 Jul 2009 19:50:12 -0400
"Bill Bradburry"
<bbradburry@bellsouth.net> wrote:
> Steve,
>
>
>
> If I understand your observations.embedded below.
>
>
>
> Bill B
>
> _____
>
> From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net]
> On Behalf Of sboese
> Sent: Monday, July 13, 2009 6:24 PM
> To: Rotary
motors in aircraft
> Subject: [FlyRotary] cold switch and injector
backup mode
>
> This weekend I had a chance to make some
observations concerning the
> previous discussion on the use of the cold switch
and the injector
> backup mode on my EC2 used with a 13B.
>
>
>
> When idling, turning on the cold switch results
in all four injectors
> delivering fuel at the pulse width that was used
by the primary
> injectors before the cold switch was turned on.
>
> Below staging manifold pressure, cold start
doubles fuel flow by
> turning on both sets of injectors, effectively
canceling staging.
>
>
>
> When idling, turning on the cold switch results
in the staging data
> bit changing from indicating operation at MAP
below the staging
> threshold to operation above the staging
threshold even though the MAP is very low.
>
> When staging is canceled by the cold start
switch, it is indicated on
> the
> EM-2
>
>
>
> With the cold switch on, gradually increasing MAP
results in a
> gradually increasing injector pulse width from
idle to full throttle
> with no discontinuity when the staging threshold
is crossed.
>
> Cold start has no effect on the fuel delivery
after the normal staging
> point has been reached.
>
>
>
> Turning off the power to either the primary or
secondary injectors has
> no effect on the pulse width applied to the
injectors or the status of
> the staging data bit.
>
> The injector disable does not work above the
staging point. If you
> kill one set above the staging manifold pressure,
you will just be
> running on one set at the normal pulse
width. This will result in
> only half power or less available anywhere above
the staging point manifold pressure.
>
> This does not sound like the way I had previously
understood the
> injector disable to work. Are you sure you
have it wired correctly?
>
>
>
> Based on the above observations, it appears that
the EC2 does not need
> to know whether or not power is being sent to the
injectors.
> Regardless of the MAP at the time, turning on the
cold switch results
> in the EC2 operating with all four injectors as
if the MAP was above
> the staging threshold but with a pulse width
appropriate for only two injectors being used.
>
>
>
> My statements below concerning the cold switch
position appear to be
> in error. The position of the Cold Switch
is not one of the things
> contained in the data log captured from the EC2
so that piece of data
> was from my memory which is poor at best.
Sorry Bob.
>
>
>
> I probably should have maintained the "Avoid
reading.." subject line.
>
>
>
> Steve Boese
>
>
>
>
>
>
> From:
>
> Steven Boese <sboese@uwyo.edu>
>
>
> Subject:
>
> RE: [FlyRotary] Re: Below staging
>
>
> Date:
>
> Mon, 6 Jul 2009 00:24:28 -0600
>
>
> To:
>
> "'Rotary motors in aircraft'" <flyrotary@lancaironline.net>
>
>
<http://lancaironline.net/lists/flyrotary/Message/46928-H.txt>
> Message Header
>
>
<http://lancaironline.net/lists/flyrotary/Message/46928-P.txt>
> Undecoded Message
>
>
>
> Bob,
>
> In contrast to when the primary injector power is
off, when the
> secondary injectors are turned off and the cold
switch on, the EC2
> indicates staging is taking place normally at the
staging threshold,
> in my case at about 20 inches MAP. The engine
doesn't go lean after
> staging is indicated, however. When idling with
the secondary
> injectors turned off and the cold switch on, the
EC2 indicates no
> staging has taken place. Of course, what the
EC2's staging data bit is
> telling the outside world and what The EC2 is
actually doing may be
> two different things.
>
> Steve Boese
>
>
>
>
--
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