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Hi George,
No experience with the EM2, but the EC2 is great.
Dual CPUs, so you have a degree of redundancy - but, even better you can play
with two different fuel maps with one stored for A controller and the other for
B controller. I leave one with Tracy's stock setting and play with the
other, that way I always have one fuel map that will run the engine to switch to
in case I really screw up something on one controller.
Ed
----- Original Message -----
Sent: Friday, May 20, 2005 4:29 AM
Subject: [FlyRotary] Re: More MAP
measurement questions
Ed, Rusty, Bill, Anyone.
Here's another question - having little knowledge
in the area, I'm considering Tracy's ECU and the EM2.
What are your appreciations of the
products.
Is it the EM2 which provides the auto tune
capability ?
George (down under)
Hi George,
I'll give it a shot. The Ec2 basically
determines how much fuel to inject using two factors - MAP (Manifold
Absolute Pressure) and OAT which basically tells it how dense the air is
that the engine is ingesting from the manifold. The Ec2 then
examines its memory settings (a different Map - read
further)programmed in its memory (which you can adjust with a mixture
knob) for that manifold pressure match. Since the manifold pressure
can vary from apporx 12" Hg to 30"Hg (non-turbo), there are a series of
memory locations generally also referred to as the MAP (MAP in this case
referring to a topological chart) of the fuel settings. If you plot the fuel
mixture settings against RPM and Pressure it looks like a 2 dim
map). So once it matches the manifold pressure it senses
through the manifold pressure sensors with the corresponding memory location
it extracts the injector timing for that MAP and sends it on to the
injectors (with corrections for air temp).
The injectors fire once per revolution of the E shaft
(which corresponds to one face of an rotor, therefore, the faster the rpm
the more frequently the injectors fire. But, it basically provides the
same amount of fuel per revolution per specific manifold pressure (which of
course is controlled by the throttle setting and engine rpm) perhaps
adjusted for Ve and OAT.
Manifold Absolute Pressure is also one parameter to
determine how well you induction system is working. At sea level the
MAP is 29.92" Hg. So when you open your throttle wide open, you would
like to see 29.92" Hg on the gauge. If you do not and see less than
29.92"Hg (at sea level) then that implies there is a restriction in your
intake and a resulting pressure loss. Less pressure means less dense
air in the manifold which means less fuel can be burnt which means less
power.
That is the reason Rusty is concerned about whether
the MAP he is seeing really reflects what his engine is seeing or some fluke
of where the sensing port is in the intake. Generally you would like
to have less that 1/2" of a pressure drop any more than that (if its real)
and you are starting to loose power potential. So if the drop is real
then Rusty probably wants to modify his intake to eliminate it - if its just
a fluke of where he is sensing it - then he does not need to go to the
trouble of designing and fabricating a new intake.
That's my take on it. Hope it
helps.
Ed
----- Original Message -----
Sent: Thursday, May 19, 2005 2:13
AM
Subject: [FlyRotary] Re: More MAP
measurement questions
Al,Rusty and All,
Excuse my ignorance here, I have absolutely
no knowledge about how ECU's work. I've heard people say that it reads MAP
settings - so what is a MAP, and if it's different because the pressure is
different at different places in the inlet, how can the computer calculate
the inlet charge and timing.
I'm confused!
George ( down under)
I'm working on
a new theory about my low MAP reading. The theory is that this
isn't a problem at all, but rather a difference in the way it's being
measured.
What’s new
about this theory? This is what I was telling you a week or two
ago. J
I apologize
for lack of clarity, causing you to have to re-invent this
theory.
Al (Also
running TWM TB)
The TWM TB has
a MAP port about 4 inches past the entrance of the TB
throat. That means I'm measuring the air pressure on the
suction side of the largest restriction in the system (from wide open
space, to 41mm tube). Since there's no significant
restriction downstream from the TB, I would guess that I could
measure the MAP at the inlet of the side housing, and wouldn't find
it significantly lower than what I'm seeing in the TWM TB. In
other words, I'm measuring the worst possible MAP, which is the
suction side.
From what I
understand, the typical (if there is such a thing) intake has a large
TB, feeding into an open plenum, then into the smaller runners that
go to the engine. If I'm not mistaken, virtually
everyone is measuring their MAP in the open plenum, before the air has
to enter the smaller runners to go to the engine. In
other words, the people who are reading 30" are doing it on the
pressure side of the largest
restriction.
I could babble
on about this, but my point is to ask where others are measuring their
MAP (turbo folks need not apply). You'll also have to give a
general description of your intake layout. I already know
that Ed and Tracy are using the "typical" situation. Is anyone
measuring MAP in the runner to the
engine?
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