GL 1200 ECU compatibility

[Rednaxs60]

No accolades yet, still have a lot to learn. Made a lot of mistakes along the way.

Have thought more about the ICU issue. These will eventually be more difficult to get. Thinking a small ECU for ignition would be a good place to start. Something like a Speeduino NO2C unit, sizes in at 2" (W) by 4"(L) by 1"(H), complete with the microprocessor. Lots of the Speeduino products being used on the old continent for ignition, fuel or both. Add in a modern day coil driver and you have a nice compact unit. Would recommend doing an ignition ECU only because a full EFI conversion is a lot of work and expense.

Check out the Speeduino forum for more information. There are options out there.

[Shadowjack]

There is a fair amount of electronic components inside this box, and there is the vacuum advance mechanism as well. Does anyone have any idea whether there's an electronic rpm advance, since the location of the pulsers is fixed? It would seem like there has to be.

[Rednaxs60]

According to the OEM device manual:

The ICU varies ignition timing based on engine RPM when the transmission is in 1st through 3rd - gearshift sensor signal to ICU. When the transmission is shifted into 4th and 5th, the gearshift sensor signals the ICU to electronically vary ignition timing according to carburetor vacuum - hence the vacuum connection. All ignition timing is done by the ICU according to the gearshift sensor signal to the ICU.

Electronic advance if required will be done by the ICU. Honda doesn't give up its secrets easily if ever, so how this occurs would be the subject of a lot of speculation.

The OEM description as to how the 1200 ignition timing is done using the ICU indicates to me that when the transmission is in 1st through 3rd, the ICU treats ignition timing much like the old style distributor. The faster the PG pulses, the more the timing is changed to suit. The ICU determines from the engine RPM what the ignition timing is and uses a predefined set of values from an ignition table - speculation.

When the transmission is in 4th/5th gear, the ICU using carburetor vacuum to determine ignition timing is using the carburetor vacuum (MAP sensor in the ICU?) and engine RPM to determine engine load that results in the appropriate ignition timing being applied. This borders on a and Speed-Density fuelling profile -very ingenious if it does. Speculation.

Just a few thoughts from an EFI junky.