I've seen these exact symptoms once before Chris.  The big clue is the engine problem as soon as you go out of mode 0.   It is an absolutely positive indication of ground noise.  In this case the noise is so severe that the EC2 thinks it is getting Store button commands when the engine is running.  It works in Mode 0 because the EC2 will not execute commands in Mode 0 when running.  I worked with one builder for over 4 months trying to diagnose and fix the problems over the phone and email without success.   I'm going to copy the trip report I wrote (below) after a personal visit to the project to make sure my own sanity was not slipping.  It just happens to include some (but not all)  of the steps that you need to look at as well as some other things that may give other builders a clue as to what other type problems crop up.  The airplane was an RV-10 but composite airplanes are prone to even worse problems if the electrical system is not laid out correctly. 

Tracy
 

On 11-16-08 made trip to Todd S. in Savanna GA to check installation and found the following. 

 

1.  EC2 was not grounded to airframe close to EC2 per instructions.  There were 2 ground wires but they were longer than acceptable and went to a noisy destination on electrical system.  The case was electrically isolated from ground by foam tape between it and the mounting bracket, contrary to instructions.   Could not sync up EM3 due to noise induced communications errors.  Even without EM2 adapter in line, unit would not consistently enter test modes (1 or 8) also due to noise.  Unit also showed a couple of instances where map table and other parameters were programmed spontaneously due to noise.   Engine would start running erratically when EC2 Mode switch taken out of Mode 0  (ground noise causing programming).   Installing a short wire to airframe eliminated these symptoms.

 

2.  At one point in testing, found that cylinder 5 and 8 were not firing.  This turned out to be due to Blue Mountain tach connection to the 5 & 8 coil driver which is not recommended.   This shunted the signal to ground when the Bluemountain was not on. 

 

3.  The crank signal was measured with an oscilloscope and found to be of low amplitude and was modulated by off center trigger wheel.   The signal amplitude varied by as much as  30% (average) and 100% after the sync gap initial pulse.  Even with the engine at highest RPM tested, the CAS signal amplitude was only +- 2.6V at the highest point.  Note,  tach on plane was way out of calibration and measured prop rpm instead of engine rpm, (not recommended).   I estimate that the engine rpm was ~ 2400 RPM.   This is much less than the sample Electromotive sensor evaluated here  (Todd’s spare)  which gave at least 12 V P – P at only 1200 RPM.   I think this is due to the mounting of the sensor offset axially by approximately .22”.   This must be corrected.

 

4.  The EC2 flow rate was found set to maximum and even this was not enough to get enough fuel flow at ~ 25% of available manifold pressure.   When  higher manifold pressures were eventually tested, the mixture went rich and was well within range of the available flow rate.   I determined that the dynamic range setting of the EC2 was way too high for this particular engine – prop installation.   This is why the customer always setting the flow rate to the inappropriate max setting because they were setting Mode 3 at too low a manifold pressure setting, probably due to the rough running at higher throttle.   The dynamic range was adjusted using Mode 2 and the mixture could then be well adjusted at all tested throttle settings when using the default inj. flow rate.    Must change the default dynamic range setting for LS-1/2 type engines and clarify the tuning procedure to caution for this situation. 

 

5.  The one remaining problem that remained in testing this installation was an occasional miss at higher throttle settings.   I think this is due to the low amplitude and modulation of the crank angle signal  causing the EC2 to loose synchronization.  If the amplitude were higher, the modulation due to non concentricity would not be a problem but the combination of the two is unacceptable.  It is hoped that moving the sensors so that they are centered on the trigger wheel  and making sure that the sensor gap is close to .020”  will eliminate this problem. 

 

Action Plan:   Configure an EC2 closer to the required injector flow rate and dynamic range for this engine so that the builder will have a much simpler job setting the EC2 up.    See if I can make the EC2 crank sensor less susceptible to crank sensor signal modulation at even low signal levels.  Even if possible, this does NOT eliminate the need to remedy the crank sensor mounting misalignment.   Send this configured controller to Todd Swazey to swap out his current EC2 controller.

 

Builder Changes Required:

 

1.  At minimum, install a short (< 12”) wire (16 ga or heavier) to airframe ground near the EC2 to the EC2 ground stud.   If possible, the mounting method for the EC2 should directly ground the EC2 case to the airframe.  This is the preferred mounting method for the EC2 but the short ground wire should still be installed.

 

2.  The crank sensor mount must be modified in order to have the crank sensor centered axially (engine axis, not sensor axis) on the trigger wheel.  Crank sensor gap should be set at .020” and should not vary by more than .003” around the circumference of the trigger wheel.  If gap varies more than this, I recommend that the wheel be removed and machined in a lathe in order to take the high points off the teeth (equalize the gap around the wheel).

 

3.  I strongly suggest that the connection to the cylinder 5/8 coil trigger from the Bluemountain EFIS be removed.   The injector driver on Pin 17 of the EC2 is a suggested replacement.  Check with Bluemountain if this is a workable solution.

 

4.  When the  replacement EC2 is received and after doing the above changes, carefully follow the suggested tuning procedure in the EC2 installation guide.   Adjust both the Mode 3 and Mode 2 setting before doing any adjustments in Mode 1.   Report results to me at RWS.