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Message
Ed,
It has been my experience, in industrial control,
environment that there are several sources of latency (delay time) on and off
delay time of the IO circuitry, clock speed of the IO controller, on and off
delay times for the controlled device, mechanical delays etc. When a
machine operator presses a control button, expecting a action to occur such as
starting a motor conveyor, a stacked latency of 5 or even 100 mS is not
perceivable. But trying to put a patterned glue line on a web moving
5 to 10 feet per second, requires accounting for the IO delay time, pneumatic
solenoid delay, air line charging time, glue head mechanical delay, glue
reaction (like a dripping faucet, the glue will form a droplet before becoming a
stream.)
When I have been up against applications like the latter,
I have found a curve fitting program that has worked very well. In
the example cited, I have run a rudimentary control algorithm and collected the
resultant data. Dump the data into the curve fitting program, and the
program will crunch the data and make recommendations for the closest formula as
well as the required formula constants. This has worked very well for some
difficult applications.
IMO a great way to work your fuel flow situation might be
to install a flow sensor. Run your engine at various RPMs recording
EC2 indications and actual fuel flow sensor readings. Dump the data into a
curve fitting program and viola. One of the best fitting programs I
have found is called XLFit (VBA add on to Excel). The program cost is
$725, but it has a 30 day fully functioning trial.
If you would like to try an approach such as this, I could
provide IO for capturing fuel flow sensor data, curve fitting program, as well
as coming up to give you a hand (since I am less than an hour's drive from your
location.)
Joe (If I stop rambling, I might actually be able to
turn on the battery masters and fire up the CPU this week end.)
----- Original Message -----
Sent: Friday, March 09, 2007 8:30
PM
Subject: [FlyRotary] Re: The truth??? /
Injector flow rate mystery solved
Ah, the old induced current caused by the
collapsing magnetic field of the injector has no place to go (quickly at
least) due to the diode. That would indeed tend to prolong the closing -
hummm up to 5 msec - now the duration - that
is surprising.
That's at least part (if not all) of the reason
why I always had to add a "fudge factor" increase over the number I calculated
for the specified flow rate. The injectors were staying on a bit longer
and therefore flowing more fuel than the specified flow rate would
indicate. OK! so now I know why I had to have a fudge factor - I feel
better and will finally be able to sleep {:>)
Thanks for the additional information,
Tracy. It will keep the rumors to a minimum {:>)
Ed
----- Original Message -----
Sent: Friday, March 09, 2007 5:20
PM
Subject: [FlyRotary] Re: The truth??? /
Injector flow rate mystery solved
Still refining the exact numbers but here is the basic cause.
The diode clamp on the injector drivers (in EC2) serves 3
purposes. It limits the inductive flyback voltage to protect the
driver transistor. It recovers some of the energy used to open the
injector thus reducing the current consumption of the system. It
eliminates arcing at the A/B injector switching relay that can cause noise
problems with the processor chips.
Unknown to me until recently, it also significantly increases the
closing time of the injector after the driver pulse ends. I thought
the delay would be negligible. The actual delay depends on several
factors but may be as much as 5 ms (!) Ed will know what a big deal
this is. The factors that go into this and how much it is magnified by
the diode clamp is still under investigation.
The good news is that there is a very simple fix. (Note, Do NOT
go out and remove the diode clamps! That isn't the fix!
Tracy
----- Original Message -----
Sent: Friday, March 09, 2007 7:13
AM
Subject: [FlyRotary] Re: The truth???
/ Injector flow rate mystery solved
I certainly don't know, Rusty. Like I
said the only thing that Tracy and I could conclude was that Mazda was
under-rating their injectors - I wondered whether it might have
something to do with the way an engine is taxed in Japan.
In any case, Tracy is clearly ignoring our
pleas for more information - poor guy is undoubtedly working furiously
getting orders completed before Sun & Fun. But, he really
shouldn't tease like that {:>)
Yes, I understand what you mean about
measured flow rates - I suspect there is something subtle about this
matter. Perhaps the current profile used to open the injectors plays
some role in this as Tracy indicated he was working on a Fix.
Perhaps a two stage or progressive flow rate profile - opens and provides
normal flow for typical automobile usage but, when wide open (like ours
are at cruise) perhaps the flow rate is more. Who knows - Tracy
Crook that's who.
Ed
----- Original Message -----
Sent: Friday, March 09, 2007 12:19
AM
Subject: [FlyRotary] Re: The
truth??? / Injector flow rate mystery solved
Tracy and I have been discussing this
injector flow rate anomaly for years -
For some reason, I was certain that the Mazda
injectors flowed more than they were rated for, but after sifting
through some old logs, that's not true for all Mazda
injectors. I sent 4 slightly used 550's to
RC Engineering, and they tested them at 547, 549, 551, and
551. If that ain't 550, I don't know what is
:-)
I guess I'm baffled now. Does Mazda
operate them at 5 volts or something, rather than 12V? That would
slow down the response
time.
Hey the HKS is a good little engine
in my opinion - not as good as a light weight rotary (which we don't
have yet - Richard! get a move on {:>)), but it'll get you
flying again.
Thanks for the comments. It can't hurt much to
try it, because I've already got people who want to buy it if it doesn't
work out. Still, it's as much trouble to install as the rotary, so
it really comes down to a weight issue, and perhaps whether I'll ever
get my redrive from
Autoflight...
Rusty
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