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 -----

From: George Lendich

To: Rotary motors in aircraft

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 -----

From: George Lendich

To: Rotary motors in aircraft

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)

 

Greetings,

 

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?  

 

Cheers,

Rusty (duty calls...)