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Lynn Hanover wrote:
Every flight is a test flight.
<snip>
Tracy makes a nice controller.
Sorry, just because Tracy has cleaned it up and it has had time to cool during shipping doesn't mean that the controller will automatically be more reliable than a homebuilt solution. Same goes for anything from MSD, Megasquirt or the Ford EFIS modules that I'm using for ignition. We've had to many people on just this list who've been able to find new and creative ways to destroy perfectly good engines for us to harbor any sense or reliability in anything other than what has been proven in flight. I think what you're saying boils down to "If you don't know what you're messing with, pay somebody with expertise to do it for you." That's a valid sentiment, but I don't think it justifies Mr. Lamar's design.
Any design should be as simple as possible, but not simpler. My opinion is that the proposed design crosses the line. He is proposing a fuel injector driver. Just a small subset of what a Megasquirt or Tracy's controller accomplishes. Lamar has provided no facility for data recording, trouble alerts, monitoring of multiple parameters, etc. The design is just the injector driver, a small part of the entire system.
He has no facility for staged injection to account for the dynamic range of the injectors. At idle, a single injector is outputting in it's lower range to avoid flooding the engine. Two injectors, what is usually needed at full power output, can not dribble slowly enough to get a smooth idle. For this system to work across the full range of RPM, you would need to be able to shut off one set of injectors at a particular RPM and then quickly adjust the mixtures on the remaining injectors to keep the engine running.
Individual leaning of cylinders? On a three rotor? Are you kidding!? Maybe on a special built engine that is trying to win an artificial race like the CAFE, but for a normal fly-a-bout? I know that I wouldn't care to have that additional workload. Four more switches and four more knobs to deal with in the cockpit for a two rotor is just an additional headache. You're also adding in the EGT gauges, which may or may not be additional work.
I can etch, drill and cut my own circuit boards. I can handle a soldering iron with the best of them. I understand electronics well enough to decipher what he has laid out here. I wouldn't reject Lamar's EFI driver on reliability grounds. It is a simple system that could be made to run rock solid with very little effort. I would reject it on the grounds that it does not provide the right combination of operational benefit vs effort ratio. For just a few dollars more, you can get way more functionality and control and free up in-flight cockpit resources. There may be ways to improve the interface...reduce the number of knobs and switches that the pilot has to fiddle with...but, then you're increasing the complexity again. Take it to the logical conclusion, and you've duplicated Tracy's development effort. YMMV.
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