flyrotary@lancaironline.net Mailing List Archive

Ed asked me about this off-line and thought this might help others. Here's my reply:

Not sure what to make of Al's experience with the secondaries. I haven't noticed this myself but then again, all our installations are so different I would not expect them to be the same.

I haven't been able to think of a reason for the secondary idle improvement. If you are seeing this too, try the following first and see what happens. Swap the primary injector connectors and see if that also improves the idle. I had accidentally swapped these (in software) during very early testing on test stand and found that the idle was worse this way but made no difference at higher power settings. Don't know why your & Al's engine would be just the opposite but worth a try (swapping the primary connectors). We can play with this and tuning when you get here if you like.

Injectors are almost never the problem. Don't look there unless ALL else has failed.

Surging at idle while in descent flight (engine probably windmilling) was fixed on my installation by enrichening the lowest 2 MAP table addresses in the high (>3000) rpm range. This can only be done while actually in-flight with the EC2 panel (kind of awkward since you are normally occupied with landing chores) or using the EM2 to edit the table off-line. With no EM2, get a bunch of altitude under you so there is no anxiety about colliding with the ground while doing this tuning.

BTW, in general, I think windmilling operation should be avoided since this puts the gears in reverse torque and the gear thrust is on the nylon snubber. Could be a problem if done for prolonged periods although I have never seen any evidence of this.

Lou's idle MAP is way out of the correct range as Al noted so something is wrong there. I can fly in level flight at MAP of 15 - 18" Hg. This is not idle.

Tracy

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

From: Al Gietzen

To: Rotary motors in aircraft

Sent: Sunday, January 14, 2007 9:38 PM

Subject: [FlyRotary] Re: engine surging at low manifold pressure

We have recently tuned the Ec2 on a 20B & although it

has helped it run a little smoother we still get alot

of roughness & surging at idle from 15 to 18 inches

Mp& especially when pulling back power Has anyone

experienced this problem? The plane has been run on

the ground, however the problem was just as bad in air

in a descent.

Lou & Paul N ES 117ES

Lou;

You’ll probably need to spend a fair amount of time tuning, with an O2 sensor readout. But my first question is about the MAP. MAP at idle ought to be more in the 10 – 11” range. Second question is have adjusted the mixture knob when it is surging to see if it can be improved. Surging is most likely with a too lean mixture.

The transistion from the ‘low’ to ‘high’ table at 3000 rpm on my 20B occurs around 13.5 -14.5” (table entries 7-9). Tuning in the transition region needs to be good, or it will cause surging as it transitions back and forth. Also; if the 3000 rpm transition gets close to the staging point, it can get really messed up if the tuning on across the stage point is not well set. I found that moving the stage point up to about 17” helps stay away from that problem.

I found that I could not get smooth running below about 1500 – 1600 rpm when running on the primary injectors (in the housings). It idled much better down to about 1000 rpm running on the secondary injectors that are out at the throttle body. In my case, that puts them about 8-9” out from the ports; so either the distance, or the MSD injectors, makes the difference.

If you find it runs better on the secondary only, there is a simple change to make. In the 20B version of the EC2, with the external staging relay, you can do what I did and put the stage relay in the primary power circuit so it runs on secondary only at low MAP; and the primary kick in above the stage point.

Hope this helps. Best of luck.

Al G

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