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Date: Sat, 21 Jun 2008 9:03:41 -0400
From:  <eanderson@carolina.rr.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Surge was The SAGA continues; More checking basics and development
 progress
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Chris, as several have pointed out if you are getting surging it is 99% likely you are hitting a lean area in the air/fuel ratio at some point.  The question of course, is what is causing it.  My experience (aborted a take off on one occassion after getting airborne due to surge - on a 2200 foot runway) is that surge is caused by a lean spot at a higher rpm.

The engine revs up until it hits the lean spot - finds there is insufficient fuel to run at that rpm - dies back down into a region rich enough to run the engine at which point the rpms starts to increase - until you hit the lean region again.

A loose manifold line will generally not cause surge - will more likely cause the engine to run way too rich at idle and low rpms.  It may indeed cause your idle rpm to be higher - but not too likely to cause surge.

The most likely curpit is the fuel map in the EC2.  If you have the EM2 I suggest you monitor the fuel map while you run the engine.  Where the manifold point is at in the display of your fuel map bars is your current operation regime.  If it is surging try to find the upper limit of the surge and enrich (heighten) the fuel bars in that region.  If the cause is a too lean mixture that should start to help it.

Good Luck

Ed


 >         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
>