Mailing List flyrotary@lancaironline.net Message #64335
From: Bobby J. Hughes bhughes@qnsi.net <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: ECU - Megasquirt geared towards planes
Date: Thu, 20 Sep 2018 07:22:46 -0400
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
With 500 hours behind a rotary I would not use a controller without manual mixture and open loop operations. I often cruise at 29” MP with FA at 15.8 :1.  If I need to land earlier then I increase FA to 13.6:1 and may increase MP and go a little richer. Take off  > than 30 MP with FA 11.2:1 EGT’s under 1600 F. You can’t use closed loop or just a lookup table for that kind of flexibility. A wideband makes tuning much easier and I have three. One for flight and one on each rotor for ground tuning and balancing. Removed and plugged when not in use. 
From a safety prospective. A manual mixture control can help overcome some partial failures. SAG, stuck injector, intake air temp sensor error, etc.  

MS3 does not support a manual mixture control directly but it appears possible using the table blending feature. Not much information available about that feature but should be easy to test. 

I also will not fly with a single controller. Electronics work until they don’t. 

Good to see this much activity on the list again.

Bobby


Sent from my iPad

On Sep 19, 2018, at 9:40 PM, Tracy Crook rwstracy@gmail.com <flyrotary@lancaironline.net> wrote:

Let’s say you are at cruise altitude and you are at WOT and 20” MAP.  You want lean of peak mixture for best economy.  Now lets say you want to climb and you want max power.  Without a mixture control, how does the ECU know to go to rich of peak for max power under those conditions?

 

Tracy Crook

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From: Matt Boiteau mattboiteau@gmail.com
Sent: Wednesday, September 19, 2018 7:05 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: ECU - Megasquirt geared towards planes

 

I always ask the question, Is there a mixture knob in a modern car? Long gone are the days of carburetors.

With EFI computers, they use a table (RPM vs MAP) to indicate which AFR to target. Megasquirt does an excellent job of this. Once you get your engine's volumetric efficiency table dialed in, all you have to do is change your AFR and MS will calculate your fueling to reach that AFR. 

 

- Matt Boiteau

On 2018-09-18 11:27:40 AM, Ernest Christley echristley@att.net <flyrotary@lancaironline.net> wrote:

 

On Monday, September 17, 2018 11:56 PM, "Matt Boiteau mattboiteau@gmail.com" <flyrotary@lancaironline.net> wrote:

And I still haven’t been convinced of a mixture knob. Let the ECU talk with the wideband & baro and do the work for you.

 

- Matt Boiteau

 

 

For mixture, one of the things you have to keep in mind is that there are situations where you'll want different mixtures that the computer can't know about.  For example, you want to go full rich on take off and landing, but lean out for cruise.  How will the computer know what is appropriate at which time?

 

I got around it by adding a pot to my throttle control and used it as the throttle position sensor.  The first half of travel controlled the throttle body cable, and the mixture was tuned lean until the throttle was completely open.  The second half of the control lever travel increased the amount of fuel in the mixture, with it topping out at about 12:1.

 

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