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You had better not doubt Tracy's products as my bird (that
you claim you want a flight in) is stuffed with them {:>).
My experience is once you have "tuned" your fuel map, then
little adjustment is required. But remember your are setting the fuel map
for basically 64 bins (yes, there are 64 used below 3000 rpm and 64 used above
3000 rpm for a total of 128 - but basically you use one or the other - mostly
the >3000). So 64 bins to cover an infinite ( or at least very large)
possible pressure points - see where I am heading?
So you have 64 pressure bins which you tune. Now
when you tune (program) in the value you desire for a bin, you have
automatically selected the Manifold pressure (as influenced by
ambient pressure). So lets say your are flying at 6500 msl with the OAT at
42F, then your intake temperature and manifold pressure are going to somewhat
different than ambient conditions (inlet temp will undoubtedly be higher and
manifold pressure will certainly be no higher (unless under boost) than ambient
and probably lower. But lets say your are at 22" HG manifold pressure and
5600 rpm and air inlet Temp is 50F.
In any case, you move the mixture control until the engine
is purring just right and then hit the store button. A value is stored
in a particular fuel map bin that is a reflection of all those
ambient conditions you are operating with at that particular moment. Now
that value will get adjusted for inlet air temperature, but that's about
it.
Now you are back flying two days later. You're
at 6500 MSL, inlet temp is the same and you have as best you can get it 22"
Hg. But, is your mixture control set exactly where it was two days before
under these conditions - or just close? Remember the manual mixture
control setting always influences the value used to determine injector on
time. Are you really at 22" Hg or just very close. The point I am
trying to make it is difficult to exactly fly two flights where conditions are
identical. So you look over at your A/F indicator and flow rate and decide
they are a bit lower than you want and you bump the mixture control a
hair. All I am really saying is yes, if conditions are exactly
the same no adjustment is required - otherwise you may want to "adjust" it a bit
to meet current conditions {:>)
I personally find I am more likely to adjust the mixture
control when I am in the landing phase, as you may be varying between the two
maps at times, manifold pressure and other parameters are changing rapidly and I
really like my engine to be purring in the pattern - no burps, hesitations,
etc.
Do you need to do this - if you have done a good job
of tuning - probably not. But, lets hear from others and their
experience. I would not be a candidate for a single control system - I
like to fiddle and adjust too much {:>).
Regarding Fuel system injection approach. Like most
things Mass flow and air density systems have pros and cons. Most mass
flow systems I have seen either had some sort of flap in the intake that got
deflected X amount reflecting air flow or else had a heated element which
temperature reflected air flow, or vortex generation schemes which also did the
same. The speed density really only needs manifold pressure and
temperature ( to determine the air density). Since our engines are
positive displacement pumps they displace the the same (known) volume of
space in a revolution regardless of the amount of air in them. So if you
know the volume displaced, the only other thing you need to know is the density
of the air in that displacement space for to determine the amount of fuel you
need to inject.
So I personally believe the air density system is more
bullet proof, less complex, and lighter than a Mass Flow type. If you had
a typical mass flow system and your throttle body plenum/mount fell off
what would the system do with air no longer flowing through it. With
the speed Density system - it would go to full throttle and you would have
to use your injector or ignition switch to modulate the power. Also I
think it is much easier to have a redundant manifold pressure sensor than a
second mass flow sensor.
But, that is just a personal opinion, I've never
designed a Mass flow one.
Ed
----- Original Message -----
Sent: Friday, May 11, 2007 10:54 AM
Subject: [FlyRotary] Re: EC2
question
Thanx for the answers.
I never doubted Tracy's product, I just want to understand its
operation.
Numbers (sold and flying) speak for itself.
My question was more to the degree of automation the EC2 provides:
Is it necessary to manually (constantly) re-tune mixture or is this
automatic, once the base maps are set? Single Lever - "no need to think about"
- operation?
I remember the Speed-Density versus Mass-Airflow discussion from the
Mustang 5.0 mags and forums.
I understand that Mass-Airflow is easier to tune/play/aftermarket with,
but that Speed-Density is more efficient/precise/expensive??
I assume that a (any) controller would be rpm-adjusted by the pilot -
hold rpm.
Prop-pitch could also be pilot set (as it is in about every C/S
flying)
Prehistoric (Lycontsaurus) school also has you manage mixture - I
assume EC2 will do that all by itself, no matter what the throttle position is
(within set limits - no way to maintain rpm if pitch is too steep...)
About "the" book - well, whatever.... :)
About the rest: I wonder when someone is showing PL some "detonation"-
parts with Tracy's surviving seals! Probably he will look to the other side
and say "I can't see what you talk about!"
There is people in the world that maintain that the sky is green -
because they say so!
The weird thing is, sometimes the urge to be right is so strong, they
believe it themselves.
Even if you proof these people wrong they will come up with the most
fantastic excuses...
Had my share of contact with alike people....
If I ever get near Ed he better gives me a ride in his bird!
...or I am going to tell it that plug's up, evap-cores and pinched
ducts are "green" !
TJ :)
On 5/11/07, Finn
Lassen <finn.lassen@verizon.net>
wrote:
I'm
not Tracy but the way I understand it is you don't want this.
Why did
Powersport get such poor fuel efficiency against the Lycoming
fly-offs
in the RV-8's.
Because there was no option for leaning past max power
setting.
I guess you could have a max-power/best-fuel-efficiency
switch, but then
again you don't have a single lever. And there would
probably be times
when you want something in-between and you're back to
the variable
mixture control.
Ed has already answered the CS
BS.
Finn
Thomas Jakits wrote:
> Tracy,
>
...
> Single power-lever (maybe the prop-rpm separate or even that
> controlled by single lever), no mixture adjustment
needed...
>
> Best Regards,
>
>
TJ
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