Engine Control Unit

The engine control unit (ECU) is located inside the airbox on early bikes. On newer models, it's behind the head. Neither is a good location. Inside the airbox, it impedes access to the air filter and makes removal difficult. Behind the head, it is exposed to weather and engine heat. But there's not much unallocated space on a trials bike and compromises must be made.

The left-side photo below shows the “integrated” nature of the ECU. The 3 large cylinders adjacent to the connector are filter capacitors, probably for the DC-to-DC converter and the fuel pump voltage regulator. The blue rectangle is the CDI's energy-storage capacitor. There are 2 inductors adjacent to the blue capacitor, which I assume are for the CDI's DC-to-DC converter.

In the right-side photo below, the TR280i ECU is the smaller of the two. The larger one is for an Arctic Cat snowmobile.

Apologies for the small photos, they were captured from the Kokusan Denki website.

Kokusan Denki's integrated ECU concept

OSSA ECU next to Arctic Cat ECU

Earlier bikes use ECU part number 520030211. Later bikes use ECU part number 520030212. OSSA calls the ECU a “platform” with resident firmware being the distinction. The early platform used EOC17 firmware whereas the later platform used EOC19 firmware. Early-model ECUs require different downloading tools than late-model ECUs. The EOC19 firmware offers substantial improvements over the EOC17 firmware, including a global fuel trim.

When connected to a 12-volt battery the ECU and sensors alone (no fan or fuel pump) consumes 75 mA.

The ECU connector is a 34-pin unit made by JAE (Japan Aviation Electronics), part number MXA23A. I had not worked with the brand of connector previously. How one goes about extracting a pin is not at all obvious and I found doing so extremely difficult (part of the problem is the tight workspace). I learned the proper extraction tool costs a whopping $291 USD (for a piece of sheet metal)! I have added some helpful photos to the Image Carousel below.

Dual Map Capability

The only bike that claimed to have dual map capability was the TR300i “Factory”, but it may also have been available on other 2014 models. When I first started researching the TR280i, I stumbled across a cryptic diagram on the OSSA Canada website. It showed moving the gray wire from the #32 ECU position to the #12 position – but did not say why. I subsequently determined this is correct and necessary to enable dual maps.

That particular wire is labeled “map” on the wiring diagram. I found that the gray wire goes to a bullet connector under the front number plate. It plugs into a mating connector that goes to ground. This is a common arrangement for a dual map switch, whereby a CPU pin can be “floated” (disconnected externally, but pulled to a logic 1 inside the CPU) or grounded to select between two maps.

The dual map switch itself is just an SPST (single pole single throw) toggle switch.

Gray wire near headstock: ground for map 1, open for map 2

Dual Maps are selected via ECU pin 12, not pin 32

Dual Map Experiment

A long time ago, I loaded the 300cc Factory map into my TR280i and experimented with unplugging the gray wire at the bullet connector while the engine was running. I was not sure I could tell the difference between the two maps by riding the bike in my yard, so I used K-Scan while the bike was idling.

There was no change in ignition timing, and the idle speed and injection timing bounces around enough that I did not see a change out of the ordinary when I unplugged the map connector. One of the members of my trials club has a 300 Factory. He says that if there is a difference between the two maps, it's not much.

The latest EOC19 maps offer dual map capability for 250, 280, and 300. Unfortunately, they are “road” maps mated with either a hard or soft trials map. This is not a useful combination for me. What would be useful is to have both a hard and soft map mated together. Doing that after the fact would require reverse-engineering the map format - no small task. Maybe someday.