Mike,

 

Don’t know whether this may apply or not.  But, for a number of years, I always had a stumble when the injector staged (went from 2 to 4).  It would not stop the engine and you never noticed it in flight, but anytime you push the throttle past the staging point on the ground,  it would basically sag and the Air/Fuel ratio indicator would run off the lean end of the scale.  So I suspected it was a moment of too much air and too little fuel .  But, in any case even though I did  try enriching that region it never seemed to make much difference.

 

Once I completed my EFISM gadget so I could visually see the fuel map and where my engine was operating on it, it was very easy to see that the fuel map dropped off from the higher values needed for idle to lower values.  So now that I could see exactly which bars were causing the Air/Fuel ratio indictor go lean, I could start increasing those specific fuel Map bars.  It took quite a bit of increase across a region of about 3-4 bars (manifold pressure bins) but I finally got it to the point there was absolutely no hint of a stumble or sag as the engine staged.

 

So at least in my case, it was a case of the engine just being too lean in that region.  I hypothesize that when for an instance when the EC2 cuts from  the two primary injectors pumping all the fuel into the primary runners (and at this point with NO fuel in the secondary runners), that  the mixture is initially just a bit too lean and it takes an instant of time for things to get things squared away air/fuel ratio wise.  But, just a guess on my part.

 

In any case, if you have Tracy’s EM2 you can monitor those bars and see what they tell you.

 

Ed

 

 

----- Original Message -----

From: Tracy Crook

To: Rotary motors in aircraft

Sent: Monday, July 21, 2008 8:14 AM

Subject: [FlyRotary] Re: The SAGA continues; More checking basics and development progress

 

A big step in the MAP table is almost always the problem here.  Specifically, it sounds like the low end of the table (low MP) is too lean.   This would be the point where the MP is at its lowest point which is usually around 2000 - 2300 rpm (with prop on).  

 

  Don't know what version software you are running Mike but during the past couple of years the software has had MANY changes aimed at making the MAP table programming less critical and easier.  If you have recent software, the best thing to do is go back to default MAP then program Mode 3 and 2 (in that order) per the instructions before doing ant MAP table programming.  After doing this. very little table programming is usually needed.  Note that Mode 2 is no longer the program address range, it is now the injection dynamic range.  It acts like the low speed / idle jet adjustment in 'carburetor language'.  Mode 3 is the 'high speed jet' adjustment.

 

You might also try loading the alternate default MAP by resetting default MAP with the cold start switch UP instead of down.  Remember to reset the CS down after doing this.

Tracy

 

On Fri, Jun 20, 2008 at 11:33 PM, Mike Wills <rv-4mike@cox.net> wrote:

I too still have intermittent surging issues that havent been fully conquered. Doesnt happen all the time. Always in the 2000 - 3000 RPM range. Usually happens when I'm taxiing and back off the throttle. In my case the A/F reading is useless. The engine surges rhythmically at about a 1Hz rate with RPMs varying several hundred, MAP varying from high to low (hard to pin down exact numbers - its moving around too much), and the A/F bouncing back and forth from the rich stop to the lean stop. Fiddling with mixture always stops it, but its a little disconcerting (and embarassing) when it happens (usually as I'm taxiing away from the crowd at the local EAA chapter while everyone is watching). For a while I thought adding some capacity to the MAP sensing line (Dave Leonard's suggestion) had cured it, but not entirely. I'll need to get this figured out before it flies. Could be a real problem if it happens on short final.

 

I occasionally have a pretty good backfire at the secondary staging point. The operational solution seems to be to not linger in the area - just advance the throttle or retard it right on through and it seems to be OK. Advancing the throttle too slowly almost guarantees a big pop! I'm told it's particularly impressive after dark!

 

I havent worked on the tuning in months while I've been tweaking other little issues in prep for my DAR inspection. Just about ready to get back to it. I'm sure i'll get it more or less figured out eventually.

 

Mike Wills

RV-4 N144MW

----- Original Message -----

From: Mark Steitle

To: Rotary motors in aircraft

Sent: Friday, June 20, 2008 7:06 PM

Subject: [FlyRotary] Re: The SAGA continues; More checking basics and development progress

 

Chris,

As you've probably read from the archives surging is usually caused by an overly lean air-fuel ratio.  What is your A/F reading during the surging? 

Mark S.

On Fri, Jun 20, 2008 at 8:41 PM, Christopher Barber <CBarber@texasattorney.net> wrote:

Well, to continue the saga, I have not run the new 13b much since I got it running a few weeks ago due to the EM2 not showing oil pressure as it should.  It was giving me erratic readings like -1, -3 etc.  I hand propped the engine before I ran it and oil pumped through the system fine....much onto the hangar floor...alas, the sacrifices for certainty ;-).  Also, during my short runs everything heated up in the oil system evenly and the oil temp stayed pretty much in line with coolant temp.  BUT, since I was not sure if this was a gage/sender issue or an actual oil system problem I was very cautious about my few short engine runs.

 

Well, today while dreading the idea of dropping my pan, I happened across an extra oil pressure sender (still in the package) I happened to have.  I had seen it laying around for a while, but didn't give it much thought until I was thinking about dropping the pan. Low and behold, The problem was the sender.  I am getting good pressure reading now, along with coolant and oil temp. Yeah.  I am surprised at the temps as they seem to be staying in check considering the 95 + degree Houston weather.

 

I am able to start the engine, shut it down and restart it (something I was not able to do with the old engine).  It is somewhat difficult, but seems to be getting easier as I continue to tweak things (ie timing).  I am trying to do the various tuning via Tracy's manual.  To be honest a  lot of the information in the manual is seemingly abstract until I actually get to the step and/or problem.  So, tonight, I got it to run, and it seems to run better, but......

 

I am having a surging problem.  It seems intermittent, but it just may be I have not been setting the throttle quite the same way as I get use to it all.  Also, I have had the coil C/B pop on me several times now....it seems as if this is when the engine is near or at idle.  I have not had a chance to look into this as of yet.  Also, I have gotten a number of horrendously loud/powerful backfires.  Not sure what changes as the engine may have run fine.  It backfires when attempting to start.  I wait a few minutes and it may then start.  Gee, isn't inconsistent crap fun <g>

 

I just did a search of the archives on the surging issue, but have just started reading the 105 post on the topic.  Seems our own Mr. Slade had the same problem back in the day <g>.

 

Well, it is the middle of my work week and I gotta turn in soon, but I wanted to share that it seems as if actual progress is being made (hmmmm, wonder what will screw this positive statement up<g>) as the Saga continues.

 

All the best,

 

Chris

 

 

__________ Information from ESET NOD32 Antivirus, version of virus signature database 3267 (20080714) __________

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com