flyrotary@lancaironline.net Mailing List Archive

This happens when the pressure regulator is using ambient pressure only for reference. The TBI is using a reference pressure probe picking up dynamic pressure in the intake for increasing fuel flow at high power settings. I ran it with ambient only at one time, and saw exactly what you are describing.

Now I do not see the leaning out at WOT as I have seen on all the float carburetors I have tested. For example a 38mm would do fine at up to 60% power settings but will start leaning out higher up. A 42mm did fine at WOT, but I could not get it to idle right. Looking at the specifications, a 38mm carb is rated for up to 65hp only. This is the range of acceptable mixture consistency. Some carburetors are using boost valves at WOT against leaning.

It looks to me like the rotary is causing higher peak intake velocities compared to piston engines, and carburetors don’t like that very much as far as operating range is concerned.

Richard Sohn
N2071U

http://www.fairpoint.net/~res12/home.html

From: Ed Anderson

Sent: Saturday, August 17, 2013 9:54 AM

To: Rotary motors in aircraft

Subject: [FlyRotary] Re: Single Rotor Update

I have a friend who tried an Ellison on a 13B. Never could get the low end and the high end fuel flow to work together (I think the airflow range for the rotary exceeded the model he was using).

In any case, it finally failed him, destroyed his aircraft in the crash landing, but fortunately came through with no physical damage to the pilot. When he set the Ellison up so it would idle OK, he ran out of fuel flow on the high end. When he set if so the high end flow was good, he had too much fuel on the low end. Never did sort it out.

From: Richard Sohn

Sent: Saturday, August 17, 2013 9:53 AM

To: Rotary motors in aircraft

Subject: [FlyRotary] Re: Single Rotor Update

I am not really sure what is causing the problem, since some of the interior can not be opened without causing damage to crimps. From what can be seen from the outside and the results of my observations, I think there is insufficient air bleeding in the section between the pressure regulator and the spray tube, which is affecting fuel flow continuity under certain condition.

There is no information available as of the difference of the physical lay out form the original Ellison carb.

I realize that I do not have a good case for functional reliability, but I have don extensive investigation on the test stand, which clearly identified the area of concern so I can stay away from it.

By the way, after a couple of emails with ROTEC there was just silence from their side.

Richard Sohn
N2071U

http://www.fairpoint.net/~res12/home.html

From: Ed Anderson

Sent: Saturday, August 17, 2013 8:04 AM

To: Rotary motors in aircraft

Subject: [FlyRotary] Re: Single Rotor Update

So Richard,

Why causes the problem with the origination orientation of the TB – does the jet leak, fail to fee fuel in that orientation – airflow problem?

From: Richard Sohn

Sent: Friday, August 16, 2013 10:44 PM

To: Rotary motors in aircraft

Subject: [FlyRotary] Single Rotor Update

Another update, hopefully the last one on the engine.

The problem with the ROTEC TBI (Ellison) has been solved. It turned out that a statement by the manufacturer is not fully correct, if not misleading.

My problem was engine cut out at WOT. This only occurred at high speed taxi, not on the test stand.

ROTEC statement:” Because the TBI has no float bowl, it will work in any orientation, even upside down”

I found out that if the slide throttle is horizontal in a side draft configuration, you can encounter the problems I had.

The problem showed up, with the slide throttle 5deg down at the “open” end. This is the difference between the horizontal orientation on my test stand and the installation in the tail dragger on the ground.

I solved the problem with orienting the TBI 45deg up on the “open” end, after testing all variants I could imagine. This change included a unique double acting Bowden cable throttle.

The last two straight TOL worked flawless.

Richard Sohn
N2071U

http://www.fairpoint.net/~res12/home.html

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Checked by AVG - www.avg.com
Version: 2013.0.3392 / Virus Database: 3211/6585 - Release Date: 08/17/13