BD125-8 ZS190 swap and EFI conversion

[glavey]

Taking a break from stuff like a rats nest of a wiring harness and settings like crank trigger offset angle to doing something comparatively mindless like painting is a welcome reprieve. I took all of the angle brackets I used for the license plate holder and the exhaust hanger bracket outside (it happened to be a warmer-than-average day), ground them down to bare metal and primed, sealed, painted, and attempted to clear-coat. All of the paint I am using is left over from previous projects, and all of the cans were at least half-empty. I had enough primer and primer-sealer and EXACTLY enough black paint, but just a few spits of clear coat. I don't think any of these pieces will see any real abrasion except from being bolted/unbolted, so no real worry there.

Next I tackled getting the two holes drilled in the dash for the two newly found indicator lights. What a perfect job for a drill press! The previous day, I traced the outline of the white plastic light guide piece of the dash with all the indicator light holes. I then taped the outline to the front of the dash and lined it up as best I could. The drill worked as it should and gave me two very straight, smooth-ish holes where I needed them.

I wanted to keep the dash as water/weather-resistant as possible, so I needed to seal up the holes I just drilled with something that would let light pass through it. I would have liked silicone, but 1. it is too viscous to settle into having a flat surface and 2. it isn't completely clear, it's more like trying to look through a few mm of milk. I settled on epoxy; it flows well enough to have a smooth-enough surface and dried clear (but with lots of tiny bubbles). I put a piece of scotch tape over the top of the drilled holes on the front of the dash to keep the epoxy from leaking out, then flipped the dash over and filled each drilled hole to the point where the surface of the epoxy was flush with the plastic of the dash, and let it set for a day. You can clearly see the indicator light's color, although the "icons" in the dash are distorted. That doesn't really matter to me, I use the color and location of the lights for recognition; red light on the right side of the dash? temperature. Red light on the left side of the dash? engine is still warming up (or whatever condition I set for that light).

I attempted to make a engine block temperature sensor using one of the 10k thermistor and a ring terminal crimp (pictured). It did not work. I did successfully solder the ring terminal to the temp probe, but the probe short-circuited internally when I tested it afterward. I made another one that I jb-welded on. I'll let you know how it works once it dries.

I was trying to use the 10k thermistor instead of the 100k one that came with the aliexpress kit because when using the 100k one, the difference to the ECU between 60F and 100F is only 0.127 volts .With the 10k thermistor, the difference between 60F and 100F is 0.757 volts; greater resolution in the range we need it. The ECU can detect (I'm kinda guessing on the exact numbers) 0.005 volts change on the temperature input; each 0.005 v is one "step" of resolution. If there is only 0.127 volts between the numbers we gave earlier, the ECU only has 25 steps of resolution, or a resolution of (100-60)/25 = 1.6 degrees F per step. Whereas with the 10k thermistor, using the same 0.005 v step and 60-100 range, the ECU has 155 steps of resolution or 0.25 degrees F per step.

I'm still going to try and use the GM temperature sensors; they are much more robust than the quite-flimsy thermistors, but they are also MUCH bigger. I was intending to put one of the thermistors in the air filter to measure the IAT (intake air temperature), but there is just no way one of the GM temp sensors would work there. I asked on the megasquirt forum about remotely mounting the IAT sensor since I have essentially NO intake plenum or piping to speak of, it is literally air filter -> throttle body. I was told that remote mounting of the IAT sensor would work in my case (no under-hood area to trap heat and increase charge temperature; IAT essentially always equals ambient temp).

The place I have ear-marked for the IAT sensor is around about where I put the CDI when I had the aliexpress ECU installed. It shouldn't get heat soaked from the engine back there, and it will get some airflow over it when riding at speed. As for the engine/coolant temp sensor, I have three possible places in mind:

1. The same location the 100k thermistor is bolted to (look at my previous posts to see where I installed it). Problems with this location are I would have to drill out the threaded hole in the cylinder to a larger size to fit the tip of the temp sensor in, and then I would have to hold and secure the sensor there somehow. I really don't want to jb-weld anything to the engine. I could also make a ring terminal fit the sensor's tip and NOT SOLDER, but epoxy or jb-weld it on there. I would still have to secure it in place somehow; the sensor is too heavy to be left secured at only one point, especially on something as violently shaky as an engine. Pros are easy to access and replace, and reading the temperature of the cylinder, not the oil.

2. The oil channel access bolt next to the position mentioned in place 1. Problems with this location are having to thermally connect the temp sensor to the bolt, having to thread the tip of the temp sensor (I don't even know if there is enough meat on the tip of the sensor to be safely threaded), or having to find and buy multiple pipe thread adapters to go from the threads on the engine block to 3/8 NPT on the sensor, while having enough clearance for the tip of the sensor. Pros are easy (though not quick) access and replacement.

3. The spark plug hole. Make a CHT sensor with a ring terminal and put it between the cylinder and the spark plug. Problems with this location are, again lots o' vibration, having to jb-weld a ring terminal to a sensor, rendering it useless in any other situation, and lots of airflow over the sensor body while riding at speed, possibly cooling it below the temperature of the cylinder head. Pros are this would probably be the most accurate reading of the temperature we want, it can aid in tuning, and easy (though not quick) access and replacement.

I'm really not sure which location I'm gonna go with. Maybe a slight lean toward the current temp sensor location.

There were quite a few wires left over, unused coming from the ECU. Since I installed it (the ECU), I had a plan to wrap the unused wires together in a circle and tuck them behind the ECU. I tried to do this once by just stuffing the wires into the plastic wire loom sleeve in a circle, but that didn't work well. I had straighted the wires and tape them together about every 6-8 inches, then wound them on top on one another and taped them to each other, then finally putting the plastic sleeve over them. I seat does slightly press on the sleeve when installed and with a person sitting on it, but no where near enough to damage the wires inside.

I have been (and still am) wondering if the 125's and the 190's CDI is DC or AC. I can easily see that the 125's CDI got its power from the black switched +12v wire, but it is also comparatively smaller than most DC CDIs I have seen (from what I have read, DC CDIs need to be bigger because they need room for additional circuitry). It is only 1mm smaller than the 190's CDI. The 125's CDI has four wires/pins; trigger, ground, power, and output to coil. The 190's CDI only has one more ground pin. The wiring harness that came with the 190 would have the CDI getting AC power, and the 190 stator has a high voltage winding, the 125's stator (pictured) does not. At this point, since the 125 stator didn't have any HV windings, I am relatively certain the 125's CDI is DC (or at least works with DC). The 190's CDI... the wiring harness connections point to AC, but being the same size as the 125's CDI points to DC. I guess I'll have to try the 190 CDI on DC first (DC first because I am guessing that feeding 12 volts into something that usually needs 100+ won't hurt it, but doing the opposite will make the magic smoke escape). If it doesn't work on DC, then its on to AC. If that doesn't work, then I screwed something up.

I think I broke my cat.

[glavey]

We're getting close dudes and dudettes, we're getting close.

I got the gm map sensor installed without much trouble. One thing I did have to do was cut out key ways in the map sensor connector (pictured). As odd as it may be, it was cheaper to buy a clearly knock-off sensor + connector rather than just buying a connector. I bought the cheap senor/connector just for the connector, but it turns out there are different connectors for different sensors; mainly for 1 bar, 2 bar, and 3 bar sensors. The cheap sensor was a "3 bar" sensor and so was the connector. The genuine GM sensor was a 1 bar sensor. Nothing an xacto knife can't fix.

The "genuine gm" map sensor I bought did come in a acdelco box, but not the usual kind with the hologram on it. Either this is just an old-stock part and box, or the overseas sellers are getting more crafty at selling counterfeit parts. I have tested the sensor, and it does work and read as it should, so no worries thus far.

I attempted to make a holder/adapter for one of the gm temperature sensors, but failed miserably. I had a short piece of very thick gauge wire with two copper crimps on either side. I cut off the wire from the crimps and pounded the remaining bits of wire with a hammer and a punch in a vise. Then, I TRIED to re-open the two "jaws" that held the wire in place, but the copper was too work-hardened from being crimped, and I just mangled the whole thing. Oh well, I tried.

The temperature probe I jb welded on to a ring terminal worked out very well, and until I find a good way to mount the gm sensor somewhere to the engine, I'll be using it as the engine temperature sensor.

I also bought 5' of 3/16 and 5/16 fuel hose to use for all the low-pressure fuel runs, along with a fire extinguisher, gasoline-resistant sealant, various ratings of fuses, a bar clamp phone holder, and a 5/16 quick connect to 5/16 hose barb adapter. The fuel hoses are self-explanatory; I don't have an anti-gravity pump so I have to use hoses to move fuel to and from the gas tank. The fire extinguisher is, I hope, even more self-explanatory. I want this engine to remain an INTERNAL combustion engine. The fuel-resistant sealant is because when I took the fuel level sender off of the tank, I noticed that the rubber sealing washer was put in incorrectly and pinched (pictured). I don't know if that will cause a leak, but I am going the safe route and adding sealant. Fuses; so I only have the good kind of sparks. The phone holder is so I can connect the microsquirt to an app on android that gives me a choice of a few dashboards with most pertinent information easily read while I am riding. Don't worry, I have an old pre-dropped phone I am going to use for the dash display. The quick connect to hose barb is for connecting to the high-pressure side of the fuel pump. I mentioned in a previous post that the outlet on the fuel pump is supposed to be used with quick connect fittings, not with bare hose. The adapter is the necessary piece to go from the fuel pump to the high-pressure fuel hose. Note that they are called quick CONNECTS, not disconnects. You either need a special tool to disconnect these, or do what I did and buy one with a button you can press to release the adapter.

I was going to use the existing barb on the top of the fuel tank for the fuel return, but I just couldn't stop thinking that since the fuel hose going to the pump from the tank and from the pump back to the tank are the same size, if there were even a little bit of flow restriction on the return hose or the fittings, the fuel wouldn't be able to go back to the tank fast enough and cause higher-than-intended pressure on the high-side of the pump. Using a larger size hose along with larger fittings on the return route gives lots of room for high-flowing fuel. I chose a location on the tank that wouldn't be too far from the pump and not interfere with the plastic tank fairings. Mostly because of the inability to reach any other place in the tank, I chose to drill a hole near the rear of the tank, about an inch above where the tank fairing ends. Drilling the hole went without problem. I used a 1/8 npt female-female coupling, 1/8 npt male close nipple (yes, that is the correct term), a female-female 1/8 npt 90 degree elbow, and a 1/8 npt male to 5/16 hose barb adapter to make a clamping bulkhead fitting that hopefully along with jb weld will make for a leak-proof fuel tank return connection. I had to sand some of the paint off the tank to get a good bond with the jb weld. I ran out of black paint when I painted the license plate and exhaust brackets, so I had to use white touch-up paint (not pictured). The color mismatch doesn't really bother me, it is under the fairing so it won't be seem unless the bike is being serviced and the paint color wasn't chosen for aesthetic purposes, it's just what I had laying around.

I mounted and connected the gm temperature sensor that I am going to use for the intake air temperature. I chose the place I mentioned in the previous post, where the aliexpress CDI was installed. I had completely forgotten that there was an open-mesh air vent in the fairings right there. That means that the sensor will be getting at lest some airflow while riding at speed.

I connected the two "new" dash lights and they are now controlled by the ECU. The temperature light will come on if the engine/coolant sensor reads above 190F/~87C. The check engine light will come on when rpms are > 0 and the warmup fuel enrichment is >100% (100% is the calculated required fuel; 200% or 300% would be fuel added for a cold engine).

I still want to use the ignition advance inside the CDI box that came with the 190, but it is looking like almost every way I can think of using it is met with an problem that prevents me from using it.

Way 1. Go back to carb and CDI. Hahahah NOPE.

Way 2. Use the microsquirt in fuel-only mode and let the CDI control the spark timing. This one is the most promising, but there is one major problem; the crank VR sensor is the only way I have to sense the engine's position and speed. The CDI needs to use the sensor as its trigger, but the ECU also needs to use the senor to determine rpm. So both need the sensor's output, but the ECU cannot share the signal with the CDI; the CDI has a shared ground connection with the spark ground, power ground (circuitry to drive the CDI), and trigger signal (VR sensor) ground. So one lead from the VR sensor will be grounded (inside the CDI) to the same point that the spark plug and EVERY other power device grounds to. In the microsquirt manual, they warn about letting this very thing happen. It WILL cause bad interference with the rpm signal. Until I find a way to either split or isolate the VR sensor's signal, this option is no good.

Way 3. Give the microsquirt a completely flat ignition map, EVERYTHING set to 0, let the ECU output a signal exactly when it gets a signal from the VR sensor, and use that signal from the ECU to trigger the CDI to fire the spark plug. This would work, except the 190 CDI and every other CDI I have except for the one from aliexpress doesn't respond to logic-level inputs (usually 3.3v to 5v, low current) from the ECU. So unless I can find a way to drive the CDI from an ECU output, this option is not good.

Way 4. Extract the timing information from the 190 CDI and use it in the microsquirt ECU. The only "real" input the CDI has is the trigger from the crank and the only output it has is the ignition coil drive wire. The closer the trigger pulses from the crack are to each other, the faster the engine will be turning. If the engine is turning faster, it will in general, up to a point, need more spark advance, so the spark will happen closer to when the CDI gets its trigger input. By measuring the time between the input pulse (crank VR sensor) and the output pulse (ignition coil) at a given frequency, you can calculate what the spark advance will be for that given frequency.

In practice and as mentioned above, the CDI units do not respond to logic-level inputs. Also, the voltage signal from VR sensors goes positive and negative (above and below 0 volts). By themselves, the ECU and the arduino I was using to produce the frequencies, cannot drive a pin to below 0v. I do not have the necessary circuitry to make a negative-going signal, not to mention that the trigger circuitry inside the CDI might not even be driven by voltage, it maybe driven by current (as some of the earlier megasquirts were).

Unless I find a way to make the ECU and CDI cooperate and/or successfully extract the timing information from the CDI, I will have to use a pulled-out-of-my-ass, very conservative spark map on the ECU.

All that is left before I can do a test fire is to route the fuel hoses, take the bike outside, test/leak check all hoses, tank, pump, and fittings, and mount the exhaust.

Saturday, Sunday, and Monday are supposed to be above 60 degrees. I am cautiously and reservedly crapping my pants with anticipation and excrement. I mean excitement.