MPGuino on motorcycle Honda CBF125 PGM-FI

[DanielMaia]

Hi there!

Just wondering, its possible to connect a MPGuino on my motorcycle Honda CBF125? Its a electronic fuel injected version, it has PGM-FI

Its possible?

thanks!

[msc]

My first reaction is probably yes but I don't know how the bike is wired so I can't say for sure.

What do you know about the injection system and speedometer? Do you have a wiring diagram for the bike?

Assuming it's a 125cc engine I presume it's a single cylinder with a single injector. If this is the case it should be easy to monitor the injector signal. Most likely it would require no modification to the MPGuino but there are some injector drive signals that require additional circuitry to be compatible with the MPGuino.

If there is an electronic speed signal it should be easy to connect to the MPGuino. If you have a cable driven speedometer chances are you will not have an electronic speed signal and may need to create one. There are ways to do this, it just takes a bit more effort.

Mike

[DanielMaia]

thank you msc!

Yes, the injection system is a Keyhin, and its easy to see some wires connect to that device, i think it will not be difficult to know wher it is the INJ wire.

The speedometer, i have an idea, what about the magnet system used on usual bicycles? i have one connected, to see real speed, and it works great!

Maybe its only to connect the cable to the VSS, or i need other "system"?

[msc]

Everything sounds like it should be possible but I can't say for sure without knowing the system in detail.

You can go ahead and buy an MPGuino and start experimenting. If you know anyone with an oscilloscope you can make some measurements to see for sure if you have signals you can work with. Or you can buy an service manual for the bike and there should be sufficient detail in the manual to tell for sure if the MPGuino would work.

A manual will have details of the speedometer signal if there is one. Variations of the bicycle magnet approach work fine if you need to create your own speed signal.

I did look around a bit and was not able to find a manual I could download but they could be out there. I found a link for a printed manual and I'm sure there are plenty of other sources. Honda CBF 125 M Workshop Manual

Mike

[DanielMaia]

Yes, i can use a oscilloscope, so maybe o should find the INJ signal, and the speed signal, correct?

What i do expect of the INJ signal? If i put the (+) of multimeter of INJ signal, and (-) on earth/mass of engine case, should i expect a volt variation when i push the throotle?

[msc]

The first thing your looking for is a clean way to pick up the signals without causing damage to the wire harness. I try very hard to avoid any nicks at all to my wire harness. It can often be done but takes extra effort. For test measurements you may be able to take a single fine strand wire slide into the socket of the connector then routed out through the protective boot. If done carefully you can pinch that strand in the connector pin as it's plugged together. To get fine strands of copper wire just strip a length of wire and separate the strands. Use wire that has fine strands.

Most injectors will have ignition voltage on one side of the coil and the other side of the coil is switched to ground by the engine controller. On the engine controller side of the injector you will see near battery voltage when the injector is off and the voltage will drop to near ground when the injector is on. When the injector is turned off you will see a large spike that is caused by inductive kick back from the coil. The length of the pulse will vary with the load on the engine. You may need to hold the break and load the engine down with the clutch to see much variation sitting still. I should get longer when you rev the engine but not as much as when you really put a load on the engine.

you may see the signal drop low for the duration of the injector pulse then return high. This is the most common and is a direct connection to the MPGuino.

You may see the signal drop low briefly then make several very short pulses before releasing. This is called a pulse and hold drive signal. It can be handled but takes additional circuitry.

If you see anything else then try to describe it or better yet post a picture. While your playing with the scope try to get a good measurement of the low voltage when the injector is on. If the low point is more then about 0.25 volts you can add a resistor to create a voltage divider on the input and reduce the voltage to the processor pin.

If you have an electronic speed sensor take a look at the output. It will likely either be nice digital on/off or it will be a sine wave that gets smaller when you slow down to a stop. If it's the sine wave type it may have external diodes that shape it sort of like a square wave at higher speeds so you need to look at the signal down to a stop.

If you have nice digital pulses down to a stop it connects dirrectly. If you have the sine wave type a simple external input circuit will improve performance at low speeds.

Mike

[MetroMPG]

Daniel - did you ever install the MPGuino on your motorcycle? Just curious.

[hackish]

Didn't see this thread until now. I've never disassembled a honda bike ECU but there is a protocol honda used back in the day for diagnosis. With a scope or logic analyzer it should be pretty easy to grab the baudrate, then get a friend who works at the dealer to hook up the factory scantool to it. All the data should be there. As I recall it runs half duplex so expect to see everything you send.

[MetroMPG]

I'd like to bump this thread again -- anybody know of a thread about a successful MPGuino installation on a bike?