On 05/18/2011 05:21 PM, josrph berki wrote:

Ernest,

 

Will you be running Megasquirt for flight or is it a gound development tool?  Do you have any words of wisdom for someone contemplating Megasquirt?  I would really like to see an electronic analog injection / ignition system developed.  Software that controls the engine scares me.  Thanks for any help.

Analog injection/ignition systems scare me.  Well...not really.  All software systems are analog underneath.

I will be flying with the MegaSquirt, but I can throw it a lot further than I trust it.  But, that is ok.  The goal is do design the system so that it fails gracefully.  The MS gives an incredible amount of flexibility and configuration control.  It is REALLY nice to have.  So I take the benefits, but have backup(s). 

If the MS quits on me for some reason one day, I have a 3/16" line plumbed to the throttle body with a needle valve sitting next to me in the cockpit.  I've already verified that on the ground, with gas barely covering the bottom of the tank, I get flow to the throttle body.  I'd probably never be able to get the engine started with this setup using the starter, but with the wind still spinning the prop I will be able to slowly open the valve till I can maintain altitude.  Then I can make for the longest runway I can find.

That's good for fuel, but what about spark?  I'm having the MegaSquirt control EDIS ignition control modules.  The EDIS handles  all the VR pickup, dwell and other such details.  These things have proven to be very solid performers during a decade of use.  All MS is doing is getting a tach signal from the EDIS, and sending back a signal to control advance.  Two wire interface.  If the EDIS looses communication with the MS, it falls back to its limp-home mode which is 10*BTDC.  I shifted the VR so that I actually get 25*.  But, that just shifts the critical failure from the MS to the EDIS.  I don't have it wired up yet, but eventually I will have two EDIS modules running, one on Leading and one on Trailing.  The second will have its own power source, driven by the distributor shaft. 

Sure, power will degraded if all I have is the trailing plugs and I'm dumping fuel into the throttle body instead of a proper spray, but it isn't meant to be a normal mode of operation.  It is meant to get me past the crash site.  I don't have to be scared of the software, because I'm not hanging my life on it.

The only other advice I have is buy one of the MS3s.  They have a USB interface, and can datalog directly to a flash card.  I'm stuck with an MS2 for now.  Because of that, I have to use a 15yr old laptop, because it is the only one I have that has a serial port.