|
|
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
>
>
>
>
--
N93BD - Rotary Powered BD-4 - http://www.bob-white.com
3.8 Hours Total Time and holding
Cables for your rotary installation - http://roblinstores.com/
|
|