A friend emailed me asking for clarification in the “big step” update:

Did you get the stepper motor working correctly? In the vid it went to full open then I wasn’t sure if that was the secondary’s @ 60% or the mains.

I replied:

Yes, working well. At least working as well as I can test with it removed from a running engine.

The video depicts the subthrottle’s opening all the way under MegaSquirt control. This, via the cam, opens the main throttle a bit. MegaSquirt then works it back towards about 60%, by which time the main throttle is closed, as I manually adjust the CLT knob on the stimulator. CLT is megaspeak for coolant temperature, intended to represent the running temperature of the engine.

The engine would (likely) not warm from freezing to 160F in 15 seconds, so the throttle would close in many smaller steps instead of the 3 or 4 big jumps shown here as I manually turn the CLT knob on the stimulator. Also, the actual throttle opening needed for warmup will probably be less than the full amount provided by the subthrottle cam. I wont know that for sure until it’s on the engine and the engine is running

Perhaps obviously, neither Buzz nor the VW have “coolant”, at least not a self-contained recirculating coolant. Sometimes people use oil temp for this, but the engine is usually well into operating temperature before the oil gets very warm. Cylinder head temperature is a better representation of CLT on aircooled engines. On Buzz, I JB Weld’d the CLT sensor between some cooling fins cylinder #2.

I was lucky that the fins on Buzz’s head were spaced similarly to the size of the default MegaSquirt CLT sensor. What’s more appropriate, especially for a VW, is something more like this cylinder head temperature sender which goes under the spark plug like a washer. Trouble is that this is a thermocouple, which produces a small voltage based on temperature. MegaSquirt wants a thermistor, which varies resistance according to temperature.

I may hack an IAT (intake air temp) sensor, which is electrically the same at the CLT, and see if I can get it crammed between some fins.

Another complication with the VW is that you not only have to deal with the cooling tins, but what they represent: cooling air forced over the cylinder head, cooling the fins while you’re trying to read their temperature.

Many months of sporadic research have not revealed a published flow rate for the injectors on my TB. I have am considering sending them to Witchunter Performance for cleaning (probably unnecessary) and more importantly, flow testing.

Sadly, it will run about $50 to clean and flowtest two injectors (or $30 for flowtest only) and return ship them, but that may turn out to be an investment in time and/or sanity saved.

I could save the money by robbing two injectors from Buzz’s old throttle body. They are known to be 245cc/min injectors. Preliminary experiments with settings on MegaSquirt, however, indicate a pretty low idle pulsewidth, just under 2 mS. Maybe I have something set wrong, but that’s not much margin below the recommended minimum of 1.7 mS.

The snow came, but was indeed light and is mostly gone already. It’s not even supposed to freeze overnight. It’s still cold, just not the major death-to-all-fools-who-venture-outdoors that the news media might prefer. Maybe next time.

I rushed home and, after delays from trying to find and gather stuff (never organize; it’s just not worth it!), I reflashed the ECU with the latest firmware (v2.890), wired to support stepper IAC (Idle Air Control) and connected up to the JimStim.

One of the first things I had to do was some wire mods on the ECU board. By default, the stepper feature is not physically connected on MegaSquirt. The output connections are left unconnected because they can be used for any of several options; stepper IAC is just one of the options. The mod itself is very simple, adding five jumper wires on the bottom of the board.

After lots of experimenting, I also had to perform another minor mod, bypassing some current limiting resistors that are built in to protect the circuit board and wiring from shorts. I guess I will have to just leave my shorts at home.

After that, it was just setting parameters, which was a very much experimental “try this and observe” process. I eventually arrived at some workable values.

One thing to keep in mind is that my throttle body in it’s original Ninja 650 form uses a stepper motor to operate sub-throttles, but there is also a cam on the end of that shaft that operates the main throttle butterfly to provide fast idle. As I discovered experimentally, the subthrottle is completely open when the cam is operating the main throttle as far as it can. The subthrottle is at about 60% open when the cam disengages the main throttle completely. Although the partially closed subthrottle is not expected to affect normal engine operation until the main throttle is more than 60% open (and maybe not even then), I will probably remove the butterflies anyway.

One thing that I found confusing is that I was erroneously thinking in kind of “absolute position” terms. At power up, the ECU moves the IAC 350 steps (Start Value) to ensure it is open all the way. I thought of that as position 350, thinking that the system would then want to close the IAC down to 0 as the engine warms up.

I was wrong.

The two main states of the IAC, power-up and operation, are relative to one another. At power up, the ECU will use the Start Value to open IAC all the way with, in this case, 350 steps in one direction. Once the power-up routine is finished, that position becomes 0 and all temperature points are expressed as steps in the other direction from there. In my case, it then takes 145 steps in the other direction to completely close the IAC, or more precisely, to completely disengage the fast idle cam from the main throttle. It is 0 and 145 that are needed to generate the IAC Steps curve.

The other major value arrived at experimentally is the Time Step Size, basically the time between stepper pulses. The smaller the time, the quicker the motor moves, at least up to a point. I found that it seems reliable at 0.5 mS, which is way down from the default of 2.5 mS. I decided to give it a little margin and set it at 0.7 mS. It moves quickly, smoothly and quietly there.

For the entertainment value, at 5.0 mS, it sounds like an old 5-1/4″ floppy disk drive and at 10 mS, it sounds like a blender stuck on a piece of ice.

Sorry for the poor focus, but here is a bit of Blackberry video of it working.

Finally, it seems that operating the motor in the ‘Always On’ mode, where voltage is left on the motor to keep it stationary, makes the motor and driver chip run pretty hot. That mode is not really needed here, so I am running it in ‘Moving Only’ mode, which only sends power to the motor to effect an actual position change.

So, to summarize, it took me about 5 hours to make MegaSquirt open and close a little motor, but I think it still counts as a big step!

I’m sure I wasn’t the only one with a crazy month. It’s been go go go go go. I think the last of it is done.

Well, except for the weather… Expecting a bit of snow tomorrow, though it’s not expected to be much nor to stick around.

Santa thought organizing my tools might help me be good for next year, so he brought me a big rolling tool chest/organizer. I loves me some Santa. Lucky for me, Santa’s pretty cute, too.

Now that I’m not spending every evening getting the house ready for guests or shopping or whatever, I should FINALLY be able to start playing.

Today was very nice and, difficult though it was to do so, we worked on stuff around the house instead of going for a ride.

Filled the back of my truck with trash and other discardables from the carport. I still had the boxes that various Harbor Freight items came in, such as the air compressor, engine stand, welding cart, tool box cart and soda blaster. Most were at least wrinkled from humidity, if not completely warped from rain. Fall leaves, countless shopping bags (mostly from AutoZone, which is probably a hint that I should be a stockholder) and no shortage of used paper towels littered the area.

We had some aluminum frame windows that were promised to our neighbor long ago. They were stored quite literally as far back in the carport as possible. Because of the work today, I was able to clear a path all the way back there and retrieve them for him. Tiny karma gain.

I worked from about 10:30A or so until 7:00PM. If you look at it critically from a before and after point of view, all I did was make room for one more trike. More importantly, though, 2/3 of the space is clean enough to easily roll things around. Another good evening’s work and I may be able to roll the purple trike all the way back where the best work space is and work on it at home for a while.

So long as it’s not devastatingly cold or actively precipitating, the space isn’t too bad. I have a 30,000 BTU heater almost exactly like this one and it keeps a decent working area warm. I may try to cover the gap between the top of the fence and the roof of the carport to keep some of that heat enclosed.

I have been essentially storing the trike at the BTW clubhouse. The *intent* was to have it down there to work on it, but mundane life has ensured that I have had little time to pack up and head down there, compounded by the need to keep my footprint there at a minimum for the holidays. Now that our (probably) final holiday shindig there has concluded, perhaps I can make some progress working on it down there.

But first, I want to get some stuff done that is arguably easier to do at home, such as the welding I need to do to complete the adapter plate.

An acquaintance is building an airplane from a kit and whilst perusing the builder’s guide on their website, I stumbled upon a piece of advice that I had inadvertently ignored: “[your construction space] should be as close to home as possible. Driving any distance at all to work on the [airplane, trike, whatever] will drive the time to build up by unimaginable amounts. One [airplane kit] builder estimated that having to drive only four miles to work on his project doubled his construction time.”

It also says that “Good light, air conditioning or heat as the climate requires, good ventilation and good organization are essential. An uncomfortable place to work means hurried, often poor, work.”

In my case, those are almost exclusive of one another. The clubhouse is a fairly well lighted space that has a roof over it, a decent amount of work space and a few specialty tools that are absent at home. It is, however, 4-5 miles from home.

My driveway is covered but otherwise essentially outdoors, and crowded with stored tools and vehicles. It is, however, very close to home.