Viking Aircraft Engine Forum
What model aircraft are you interested in Murphy Rebel
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Wow, sounds like the Viking is now a turbine that we have to spool up to start. I might have to grab a T-62 starter and instrument the engine for fuel flow at 20% and ignitor excitation. Actually, if your point of comparison is the Rotax soft start module (which only changes the timing during starter engagement), I can see no perceptible difference in cranking time before the engine starts with or without the soft start module. I would expect the same from Viking, retard the timing during initial cranking and advance it as the rpm increases. That should take only a couple of seconds to accomplish. You also have precise control over the fuel flow timing and injector duration which should make starting easier and faster. If you want to start it like a turbine, put in a starter designed to spin the engine at 1000 rpm with no combustion assistance. That way the engine and drivetrain would never have to run in the region below 1000 rpm where kickback and loading/unloading are a problem.
It is helpful to know that the slow starting is intentional. I was not aware of that until now. Unfortunately I was missing this information and had no idea what to expect when my ECU was reprogrammed. Now I know this is normal, and can tell the guys at the airfield... no worries, it was designed to start this way. Will give it another try tomorrow and see what happens.
I have the only flying Viking Sonex with a firewall mounted battery that I know of and it won't be that way for long. I am eager to get the lead out of the tail. Tail mounted batteries have long wires with the consequent voltage drops which will make the starter run slower. Jan's new scheme is a large asset in this circumstance because with timing retarded a slow turning starter has a much better chance than with the previous kickback situation which was really hard on starters. Another side effect is that the cold oil has a chance to get some pressure before the thing comes completely alive. It has taken me some thought to get used to the idea because it is not like anything I have had experience with before. The fact that the remainder of the starts are fairly fast is good. If you need an aerial restart for whatever reason it will be fairly prompt.
Just got off the phone with Howard and he could not be happier. (Other than going in for small surgery) He now can start the engine any time, without worrying about it bogging down / kicking back from too much timing advance or excess fuel being introduced early. The process of gradually advancing timing and fuel is working and provide a much smoother start than the Rotax. It is now the way we envisioned the final outcome. As Howard pointed out, subsequent starts throughout the day are also soft but will take less time. He also said he has not actually timed a start and if it is anything like other engines, the real time is more like 5-10 seconds for the first start and 4-6 for subsequent starts. The method is to hold the starter until the engine has fully spooled up to idle speed.
"Every Honda I have starts within a couple of seconds of being cranked, which is what we should expect"
Go put your Honda in 3 gear. Start it and report back. There are always compromises to be made. The Viking does not disengage the transmission or propeller for starting. It does not have a 28lb steel flywheel. Same is true for the Rotax. Direct drive engines do not have any of these issues but are not quite as smooth at operating rpm.
Howard, are you running the new upgraded ECU software? I am not sure I buy the engine "helping" the starter comment, especially if you are running the starter for 15-20 seconds or more at a time. . That is well outside the duty cycle of the starter. Loading and unloading the overrun starter clutch is also not good for stater life. I am not sure why a half running engine is considered good, especially if your other starts the rest of the day are normal as you indicate. Every Honda I have starts within a couple of seconds of being cranked, which is what we should expect.
I have resigned myself to making sure the battery is fully charged so it will turn the engine for the requisite 15-20 seconds. If I just keep the starter button engaged until the RPM hits 1200 or so we are good to go. It will make 3-5 false starts before deciding its ready. I just gotta power thru. Unusual starting arrangement. Starts are normal the rest of the day.
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