The Orion ECU has the ability to use two injectors per cylinder. The way these injectors are implemented vary for different applications. If you use one fuel and the primary and secondary injectors does not differ too much in size, then the Ratio method is preferred. If you want to use different fuels together and the secondary injectors is a lot bigger than the primary injector, then the Graph method is preferred. On the hardware side, there is also different wiring configurations for different firmware. If there are enough drivers for all the injectors, then they can be used. If there are not enough drivers, then an extra electronic relay and isolating diodes are used to power the secondary injector’s separately. So please see on the wiring diagram. The hardware connections do not affect the software settings if it is the same method. Note: This feature is only available on specific firmware. ask your dealer on it before you buy.

If you are not using micro fueling, set it to ‘OFF’ to free up some microprocessor time.

Ratio Micro Fueling

This feature uses the primary injector at low manifold vacuum and when the manifold pressure goes high, it will add a secondary injector to increase the fuel amount to the engine. This will allow the engine to be tuned more optimally on low and high loads. This is necessary for high boost applications where the range of the injector’s usage become limited. There are two limit values and the ratio value. If any of the two limits are reached, then micro fueling will be activated.

The ECU will calculate the difference in injector time between one and both injectors, so that the same amount of fuel enters the engine under the same conditions. This method should make the transition as smooth as possible. This is done by decreasing the total injector time by a fixed % which is calculated in the explanation below.

The Injector ratio adjust % field is calculated by the primary injector cc divided by the total injector cc multiply by 100.

Example: Primary = 100cc, Secondary = 200cc.

Compensation = Primary Injector x 100 = 100cc x 100 = 33%

Primary + Secondary Injectors 100cc + 200cc

If you are not sure on the injector sizes set the 2 limit values high so that the secondary injectors stay off. Tune the engine at 3000RPM’s with the primary injectors up to a load where the injector duty % is around 70% . Set the A/F Ratio with the Fuel Ratio setting to be at stoic or 45%. Now start with 50% Injector ratio adjust value. Decrease the two limit values so that the secondary injectors start to operate. Reduce or increase the Injector ratio adjust % so that the same air fuel ratio at the same load is reached. You may need to reduce the throttle to disable the secondary injectors, while changing the Injector ratio adjust %. Now adjust the % setting till the Fuel Ratio setting to 45% like with single injectors.

The Injection duty limit is one of the limit values where the secondary injectors will be implemented. If you set it at 70% then the moment the primary injector reaches this value, the secondary injectors are implemented. This will result in a combined lower injector duty cycle.

The Injection duty time is the other limit value where the secondary injectors will be implemented. If you set it at 12 milliseconds then the moment the primary injector reaches this value, the secondary injectors are implemented. This will result in a combined lower injector time.

Note: There is a dead band implemented on both limits so that the injectors do not become erratic when you cruise at this changeover load.

Graph micro fueling

This feature is ideal for Methanol Injectors. It will not influence the primary injector time like the ratio method. It will just bring a secondary set of injectors in at a certain boost pressure and progressively adjust the injector time for the secondary injectors on a graph in milliseconds. If you select Graph, a second graph on the Fuel graph will become visible. Click on the fuel graph menu button and set the graph as follows.

The brown graph will be for the primary injectors and the blue graph for the secondary injectors. There is no real time display for the secondary injector value but the milliseconds are exactly as on the graph where the orange boost bar cross. Note that when these injectors do come in working zone, you need to keep the primaries constant or reduce them under the same pressure. The reason is that they may be close to the maximum duty cycle of 100%. This graph is interpolated.

Check the relevant drawings of which drivers will be used for this micro fueling.