ChinaRiders Forums - View Single Post - BD125-8 ZS190 swap and EFI conversion

glavey · 03-01-2019, 10:58 PM

Let's say the ECU needs a nominal 12 volts to operate. The voltage on the +12 wire into the ECU must be at least 12 volts higher than the voltage on the ground wire going into the ECU. The ground wire could have 1000 volts (referenced to earth) on it and if you connect 1012 volts to the +12v wire, the ECU will operate as it should, provided there is no reference to earth ground anywhere on the ECU. If the ECU's ground voltage is pulled up too high from things like stray inductance, a magnetic field collapsing, rapid high power switching, etc, then there won't be enough voltage difference the +12v and the ground at the ECU to let it keep functioning properly and it crashes and resets.

So I need to suppress that inductive spike. This is a bit beyond my knowledge set, since I can't really "intercept" the ground signal like I can on a relay; the starter motor is more-or-less permanently attached and grounded to the engine, so I can't exactly put a diode in-between the motor and the engine. I started a thread on the arduino forum asking for assistance with suppressing the inductive "kick" from the motor. I already have a few things I can try.

That thread on the arduino forum also made me realize that I think the wiring on this from-china ECU is probably its weakest link. ALL the wires are too small gauge to carry enough current and not have dramatic voltage drop and too short to isolate electronically noise components, power hungry components, and sensitive analog components from each other. You can see how small the ground wire is in the picture.

For this EFI kit to work WELL and RELAIBLY, I will most likely have to crack open the case and hopefully be able to solder on some thicker gauge wires, proper grounding wires, and sensitive analog signals shielded all the way to the ECU box (notice I said work well and reliably, not just work. I am sure that this kit will start and run and engine, but it will at some point probably have an electrical gremlin or two that will be very difficult if not impossible to squash without opening the ECU.)

I am going to try to keep the wiring coming from the ECU as close to "stock" as I can so I can test the kit as anyone else who purchased it would have it wired. If it turns out that I cannot reliably control the engine with the stock wiring, I will dive right in to the ECU case and crack it open like a walnut. I don't want to open the ECU just yet, I haven't even tried to start the engine with it yet and I don't want to condemn the ECU because I just thought I would have a problem with it.

The fuel tank fitting, of course, requires drilling a hole in the gas tank. Drilling a hole in metal causes heat, hot sharp shrapnel, and possibly sparks. Gas tanks have... gas in them. Gas + oxygen + spark = the kind of boom you want INSIDE your engine, not outside. I drained out all of the gas from the tank and took off the filler cap. Now I'm just letting the remaining gas and gas fumes evaporate and leave the tank. With the temperature so low, that may take a while. I'm going to have to get all of the vapor out of the tank because I realized that I really do need the tank on the bike to know where I can route the fuel hoses and where to put the pressure gauge so it can be viewed with all of the fairings on. So I can't run the hoses, install the return fitting, or position the pressure gauge before I get the tank nice and empty.

I was able to sync the timing between the engine and the ECU despite the reset issue. One thing that made it much easier was a printed pulley/crank/flywheel degree ruler. This site lets you enter the circumference of the wheel you want to degree and gives you a printable degree ruler you can tape/glue to whatever you need. I temporarily stuck it to the magneto so I could see the degree markings through the peep hole on the engine. Of course, I could only do this at cranking speed, not idle. I had to remove the intake manifold and keep the spark plug out so the engine could turn as fast as possible. With the spark plug in, the timing jumped between 10 and 20 degrees BTDC because on one rotation of the crank, the motor had to compress a cylinders worth of air, slowing it down a lot, and on the next rotation of the crank, the exhaust was being pushed out, so very little slow down there.

o2 sensor and exhaust spring hooks welded in
install return hose fitting in tank
plumb fuel hoses
solve or minimize reset issue
permanently mount exhaust
wait

That's it. The last 10% is the longest 10%.

03-01-2019, 10:58 PM	#58
glavey Join Date: Oct 2018 Posts: 74	Let's say the ECU needs a nominal 12 volts to operate. The voltage on the +12 wire into the ECU must be at least 12 volts higher than the voltage on the ground wire going into the ECU. The ground wire could have 1000 volts (referenced to earth) on it and if you connect 1012 volts to the +12v wire, the ECU will operate as it should, provided there is no reference to earth ground anywhere on the ECU. If the ECU's ground voltage is pulled up too high from things like stray inductance, a magnetic field collapsing, rapid high power switching, etc, then there won't be enough voltage difference the +12v and the ground at the ECU to let it keep functioning properly and it crashes and resets. So I need to suppress that inductive spike. This is a bit beyond my knowledge set, since I can't really "intercept" the ground signal like I can on a relay; the starter motor is more-or-less permanently attached and grounded to the engine, so I can't exactly put a diode in-between the motor and the engine. I started a thread on the arduino forum asking for assistance with suppressing the inductive "kick" from the motor. I already have a few things I can try. That thread on the arduino forum also made me realize that I think the wiring on this from-china ECU is probably its weakest link. ALL the wires are too small gauge to carry enough current and not have dramatic voltage drop and too short to isolate electronically noise components, power hungry components, and sensitive analog components from each other. You can see how small the ground wire is in the picture. For this EFI kit to work WELL and RELAIBLY, I will most likely have to crack open the case and hopefully be able to solder on some thicker gauge wires, proper grounding wires, and sensitive analog signals shielded all the way to the ECU box (notice I said work well and reliably, not just work. I am sure that this kit will start and run and engine, but it will at some point probably have an electrical gremlin or two that will be very difficult if not impossible to squash without opening the ECU.) I am going to try to keep the wiring coming from the ECU as close to "stock" as I can so I can test the kit as anyone else who purchased it would have it wired. If it turns out that I cannot reliably control the engine with the stock wiring, I will dive right in to the ECU case and crack it open like a walnut. I don't want to open the ECU just yet, I haven't even tried to start the engine with it yet and I don't want to condemn the ECU because I just thought I would have a problem with it. The fuel tank fitting, of course, requires drilling a hole in the gas tank. Drilling a hole in metal causes heat, hot sharp shrapnel, and possibly sparks. Gas tanks have... gas in them. Gas + oxygen + spark = the kind of boom you want INSIDE your engine, not outside. I drained out all of the gas from the tank and took off the filler cap. Now I'm just letting the remaining gas and gas fumes evaporate and leave the tank. With the temperature so low, that may take a while. I'm going to have to get all of the vapor out of the tank because I realized that I really do need the tank on the bike to know where I can route the fuel hoses and where to put the pressure gauge so it can be viewed with all of the fairings on. So I can't run the hoses, install the return fitting, or position the pressure gauge before I get the tank nice and empty. I was able to sync the timing between the engine and the ECU despite the reset issue. One thing that made it much easier was a printed pulley/crank/flywheel degree ruler. This site lets you enter the circumference of the wheel you want to degree and gives you a printable degree ruler you can tape/glue to whatever you need. I temporarily stuck it to the magneto so I could see the degree markings through the peep hole on the engine. Of course, I could only do this at cranking speed, not idle. I had to remove the intake manifold and keep the spark plug out so the engine could turn as fast as possible. With the spark plug in, the timing jumped between 10 and 20 degrees BTDC because on one rotation of the crank, the motor had to compress a cylinders worth of air, slowing it down a lot, and on the next rotation of the crank, the exhaust was being pushed out, so very little slow down there. o2 sensor and exhaust spring hooks welded in install return hose fitting in tank plumb fuel hoses solve or minimize reset issue permanently mount exhaust wait That's it. The last 10% is the longest 10%. Attached Images
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