Hi Ed, The method you used will work fine for eliminating the staging bog.
There have been enough comments on this subject so I might as well get into
some of the underlying causes.
I mentioned before that it was related to the difference in turn-on and
turn-off times of the injectors. The turn-on time is slower than the turn
off time, especially with the snubber mod which speeds up turn-off. So,
at staging point, the injector pulse width ( IPW ) is cut in half at the
same time as the controller enables the secondary injectors. If the t-on
and t-off times were equal, the injected fuel would be almost the same as
just before staging. BUT, the actual time the injectors are turned on is
less than 1/2 of what it was because a higher percentage of the IPW is used
up in the t-on injector delay , result is a lean condition. When the
throttle is advanced more, the IPW gets longer and so the percentage of IPW
"wasted" in the t-on delay is less and the mixture returns to normal.
If the staging point is made at a higher manifold pressure (and longer IPW),
the effect is not as great and that's why tuning out the "bog" is easier.
This describes the results with the same flow rate injectors in both primary
and secondary injectors. When different flow rates are used, the picture
gets more complicated. Mode 6 (staging flow rate differential) is even
more important in these cases. That's why I now ask for what injectors are
used so I can roughly pre-set Mode 6 to make tuning it easier.
Also a factor in how difficult the bog is to tune out is the setting of Mode
2 (Injection Dynamic Range) but that is a longer subject. Suffice it to
say that setting Mode 6 and 2 up prior to MAP tuning in Mode 1 will make
your life easier.
Hope this helps in understanding what is going on.
Tracy
On Tue, Feb 17, 2009 at 5:45 PM, Ed Anderson <
eanderson@carolina.rr.com>
wrote:
Tracy, for what it's worth, I also see the leaning of the mixture at the
staging point which happens to also coincide with the staging "bog".
I never knew what was causing the bog and since I don't fly there nor
encounter if during flight, it's never really bothered other than wondering
about what was causing it.
Once I had a screen display to watch the bin pointer, the staging point and
the air/fuel mixture on the same screen, all at the same time, it became
very clear that leaning of the mixture (or at least that is the indication
of air/fuel ratio indicator) is happening.
As my bin pointer moves from the hump at the idle (low rpm) region, it jumps
from the low rpm map to the high power/manifold pressure chart above bin 64
- not staged yet. Still no bog, but as it moves a few bins higher the
air/fuel indicator dives from rich side to off the bottom of the scale lean
and the bog begins. At this point my staging sign goes from 2 injectors to 4
injectors indicating that the EC2 has signaled staging. It last for approx
3-5 bins (memory's a bit vague here) before the A/F indicator comes back up
the scale. So something is causing a lean condition. I always speculated
that it had something to do with the air/fuel mixture in the secondaries
making the transition from "dry" to wet - but couldn't quite convince
myself.
The only way I have been able to eliminate the bog is to increase the
richness of that region (3-4 bins) to approx 80-90 (out of 255) which is not
really a rich setting, but it works and has eliminated the bog. I enrich
each bin's bar watching the A/F indicator as soon as it stops going
completely off the lean end of the scale, I stop and that seems to work for
me.
Ed
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.comhttp://www.andersonee.com
http://www.dmack.net/mazda/index.htmlhttp://www.flyrotary.com/http://members.cox.net/rogersda/rotary/configs.htm#N494BW
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