Ignition Control Module (ICU) Replacement Project for the GL1200 non-FI models

The forum has been rather quiet so I thought I might do a what-if thread regarding the GL1200 engine ignition control module (ICU). Don't know if I have covered everything, but this is a topic that many may have been thinking about, not so much doing this type of project but what if this little ICU box fails.

What is Needed for Ignition Only ECU System – GL1200 ICU Replacement

Background

Ignition Control Module (ICU) for the GW GL1200 carbureted models are aging and will start to fail. The ICU controls the ignition timing. It is designed such that in 1st through 3rd gear the engine timing is electronically varied in relation to engine speed. In 4th and OD (5th) gears the gearshift sensor signals the ICU and the ignition timing is varied in relation to the engine vacuum.

The issue with this ICU is that an owner is not able to change the ignition tune. An owner can set the engine crank and camshaft alignment (“T1”) and check the ignition idle timing (“F1”). The OEM uses timing marks that are scribed on the engine flywheel. The auto industry and aftermarket ECUs do engine timing in degrees, generally BTDC.

The GL1200 engine idle timing is approximately 13 degrees BTDC, maximum engine timing is at approximately 3000 RPM at 38 degrees BTDC. The timing map for the ICU is based on the timing if a distributor was being used and is a good general approximation of what the engine timing should be; however, a newer ignition control unit that can be adjusted and tuned can further dial in the ignition timing requirements for better engine performance and operation.

What are the choices? An old, used ICU, or a new aftermarket ECU unit such as the Speeduino NO2C (Normally Over 2-Channel) unit is a good replacement alternative. There may be others available, but this Speeduino ECU unit is compact and about the same size as the OEM ICU, and is a good option for the DIY crowd. No affiliation, but I do like the open-source architecture.

With a new aftermarket ECU unit, you would need the tuning and analytics software for the new ECU unit.

Parts/Components for an EFI system:

Fuel injectors
Spark units (coil driver(s))
Coils – or facsimile
Crank/camshaft trigger wheels
Crank/camshaft sensors – Hall Effect or VR
IAT sensor
CLT sensor
MAP sensor
TPS
ECU
IAC components
Wide band O2 sensor unit with controller

Changing carbureted ignition to a more modern ECU configuration:

Coil driver
Crankshaft trigger wheel
IAT sensor
CLT sensor
MAP sensor
ECU
Hall Effect or VR sensor(s)
Wide Band O2 sensor and controller (optional)
Tuning and analytics software

Data required for new ECU

Coil driver
Coils
IAT/CLT sensors
MAP sensor

Recommended Changes

New coil driver such as Bosch 211 4-channel coil driver – data is available and widely used in the aftermarket EFI world
36-1 crankshaft trigger wheel – readily available and a go to crankshaft trigger wheel in the aftermarket EFI world
Honda OEM IAT/CLT sensors – sensor data can be easily ascertained
MAP sensor should come with the new ECU interface board – highly recommended
Crankshaft Hall Effect sensor – Cherry GS100701- recommended as there is no requirement to use a VR signal conditioning board

Discussion

The GL1200 engine is equipped with a crankshaft trigger wheel, and can easily be retrofitted with IAT/CLT sensors. Removing the OEM spark units and installing a new Bosch 211, or equivalent coil driver is a wiring project (can use the existing wiring). The MAP sensor is easily installed as well, and engine vacuum taps are readily available. The wasted spark system can be kept.

A wide band O2 (WBO2) sensor and controller would be an option, installing one and being able to monitor the engine AFRs would allow for additional ignition timing and carburetor tuning.

There may be a tachometer issue, but if the system is maintained as close as possible to the OEM design it should not be an issue.

Coil dwell will and coil voltage compensation will be an experimental exercise as there is no data available to dial in these two issue. The good news is that the recommended start settings are good enough to get a person back on the road.

I did an engine timing mod for my '85 FI model. I made an engine case timing pointer and set the #1 TDC position using the 36-1 crankshaft trigger wheel. This is located in the timing belt area, and on the left side. Works very well and is easier to use than the engine timing port. The 75mm crankshaft 36-1 trigger wheel would be preferred from a timing perspective in that each valley and tooth represents approximately 5 degrees of timing advance/retard.

As I have mentioned, the OEM uses timing marks that are scribed on the flywheel, the new aftermarket ECUs use timing degrees. If this is a project that you would pursue, best to change to using engine timing in degrees.

This project would be good for the 1984 GW GL1200 as it has a different ignition setup than the 1985 to 1987 GWs.

Having mentioned the above, let’s have a round table discussion on the merits of such a change/project, are there other components required, and are there any takers. I am not going to buy a carbureted model as my ECU replacement project is keeping me quite busy.

Interesting idea, not sure I follow all the requirements. I'm guessing that if the ICU on mine failed, it would be something I'd need to do??

Mike - easiest fix if the ICU goes south is to replace with an old identical PnP ICU. If you are adventurous, a new unit as I am mentioning. I am going to do a wiring diagram to indicate what I think the wiring should be for a Speeduino ECU that has the NO2C interface board, maybe a UA4C as well. Here is a picture of the size of the Speeduino NO2C in a case, small and compact:

Coil driver recommendation - Bosch 211 4 channel. Recommend changing out to this single unit because it is widely used. I have one on my '85 FI model using it for sequential ignition:

Crankshaft trigger wheel:

Hall effect sensor - Cherry GS100701:


The Hall Effect sensor needs 5VDC power and ground, both are from the ECU, The signal wire goes to the ECU, the board is configured for a Hall Effect sensor instead of a VR sensor, and it requires a 1K ohm pull-up resistor (should be on the board).

IAT/CLT sensors are from an '85/'86 GW FI model.

A bit more information to digest. The NO2C Speeduino interface board is the same size as the Arduino Mega 2560 microprocessor - 8X4X0.2 cis.

OpenLogicEFI (previously Detonator) Pre-Ignition X2 assembled - NO2C clone - $99.00 USD w/4 bar MAP sensor installed – QTY 1. Comes with the connectors:


This is Speeduino compatible NO2C clone. It allows for future proofing if you should go further than ignition only.

Supports up to 4 cylinders of fuel and ignition control using batch (paired) injector mode, and wasted spark

2 Injector Channels
2 ignition Outputs
4 Fully protected pre-configured input channels for oil pressure, fuel pressure, and others
2 trigger inputs for crank and cam shaft position sensors
1 spare digital input
1 dual VR conditioner mount (mount will have to be installed)
1 SMD Map sensor mount location
1 DRV8825 Stepper module mount location
4 customizable high-current (1A max ground switching) spare outputs for idle control valve, boost control, VVT and others
1 pre-configures output for tachometer
2 pre-configured outputs for fan and fuel pump control via ground switching relay
1 flex fuel sensor input
1 serial3 header used with HC-05/HC-06 Bluetooth module

An Arduino MEGA 2560 microprocessor is needed, order at same time – QTY 1 - $20.00 USD

36-1 trigger wheel – Qty 1 - $60.00 CDN
Bosch 211 coil driver with connectors – Qty 1 - $34.00 British Pound
Cherry Hall Effect sensor – GS100701 – Qty 1 - $38.00 CDN

Lots of components used are from salvaging parts/components at a scrapyard.

Combo Package of Tuner Studio MS Ultra and MegaLogViewer HD - $130.00 USD (best package for use). Can download free versions to play with and get used to the features.

Various other components such as an IAT and CLT sensor, and others – not a huge expense.

Install of the crankshaft Hall Effect sensor using 1" angle aluminum. Fits where the original VR sensor is located. Recommend to use the lower mount. Use the upper mount to install your new engine case timing pointer. 5VDC power and ground for crank Hall Effect sensor is from the ECU:

New engine timing pointer installed using the upper crank VR sensor mount position:


No takers yet?

Wow good work

More thoughts on this type of project. Have most of the components that I think are needed for a pilot project, bench test of such a project. Need a Hall Effect sensor, wouldn't hurt to have a spare available.

I have the 36-1 trigger wheel. The 1500 engines have a 12-1 crankshaft trigger wheel that will work as well;

Engine timing mark pointer, yours may differ, but this is the concept - just have to miss the timing belt. This picture is what I have installed on. my engine:

This picture is what I had installed with the 36-1 trigger wheel, two different setups but achieve the same aim:


Marking the 36-1 crankshaft trigger wheel for timing is easy. Each valley is approximately 5 degrees of timing, as is a tooth - the width of a tooth is approximately 5 degrees of timing. A piece of tape on the 1500 trigger wheel and marked for #1 TDC and then mark 4-5 mm for each 5 degrees of engine timing. 36-1 trigger wheel with timing marks:

The CLT sensor can be installed using a coolant pipe from an FI model:

The IAT sensor can be installed in the air box lid. A wide band O2 (WBO2) sensor can be installed in the exhaust system. Probably not needed but will assist in tuning the engine.

An engine simulator such as one of these:


Edit: have the software and some spare Arduino Mega 2560 microprocessors so I can do a mock tune (I think).

Have some more homework to do, but a plan is coming together. This will not be a "quick get on with it" project. More to follow.

Quick note on this topic. Have been reading in the different forums that these ignition control units are needing to be replaced, as well as the PG sensors. May give credence to having this project continue.

Yes I think finding viable repair/replacement options is definitely worth the effort, and your contributions are much appreciated!

I know that the Speeduino ECU will do ignition only. Was checking my ECU install, reverted back to paired injectors to determine if the dash tach would work, but the engine would not start because the ECU would not fire the injectors. The igniters were firing. So ignition only is possible, but need to determine the component list and then figure out how to do a bench test with the engine simulator I have. Looking for a suitable sized unit such as the NO2C (normally over 2 channel) Speeduino ECU.

NO2C type from openlogicefi Pre-ignition X2 Assembled - fully Speeduino compatible with MAP sensor: https://openlogicefi.com/shop/p/preignitionx2

3D printable enclosure for the NO2C at: https://www.thingiverse.com/thing:4596444#google_vignette

Picked the NO2C because of the small footprint, smaller than the OEM ICU - approximately 45 by 100 mm, 1 cm tall. A consideration is "future proofing" the install, can upgrade to a complete EFI system down the road with two injector (paired injectors) and wasted spark.

For this ignition only install only need to specify wasted spark.

A suggestd trigger wheel is 36-1. Works well on its own with the Speeduino. You can use jut about any trigger wheel that can divide evenly into 360 degrees. A 12-1 from a 1500 would be suitable as well.

These are the specs for the Pre-ignition X2:

• 2 Injector output channels.
• 2 Ignition output channels with selectable logic levels (12V/5V).
• 4 Fully protected pre-configured input channels for CLT, IAT, TPS, and O2 sensors.
• 2 Customizable spare analog inputs for oil pressure, fuel pressure, and more.
• 2 Trigger inputs for crankshaft and camshaft position sensors.
• 1 Spare digital input (most often used for vehicle speed).
• 1 Dual VR conditioner mount (VR conditioner not included).
• 1 SMD MAP sensor mount location (pre-installed sensor optional).
• 1 DRV8825 stepper module mount location for stepper idle control valves.
• 4 Customizable high-current (1A max ground switching) spare outputs for idle control valve, boost control, VVT, and more.
• 1 Pre-configured output for tachometer.
• 2 Pre-configured outputs for fan and fuel pump control via ground switching relay.
• 1 Flex fuel sensor input.
• 1 Clutch switch input (ground switching only).
• 1 Serial3 header often used with HC-05/HC-06 Bluetooth module (see Speeduino Wiki for setup instructions)

The specs are good for a fully functional EFI system. Could have used this on my '85 FI model for the ECU replacement project.

Would have to determine what is required for the tach. Would expect that the tach signal is from the coils, unlike the '85/'86 FI models that use numbers 1/3 injectors.

Always a project to be had.

More info regarding the Speeduino ECU. There are developments I have not been aware of until now. There are Speeduino clone boards that do not use the Arduino Mega 2560 as a separate microprocessor. These two boards are: C2C - compact 2 channel at: https://diy-efi.co.uk/product/c2c. and the Ocelot (based on the UA4C) at: https://wtmtronics.com/product/ocelot/

The reason these Speeduino compatible boards are so small is that the Arduino microprocessor has been incorporated in the board design. This has the advantage of where to install the ECU. The C2C is about the size of a pack of cards. The Ocelot is not much bigger.

A bit more info to hoist in regarding this project, and even a full EFI system. These two ECUs are good for a full EFI system, with some limitations.

Cheers