Moss Motors PowerCard Fuel Injection Controller

Finding a location for PowerCard

To be within easy access for tuning while driving we suggest mounting PowerCard in your glove box. This will give it a safe place, out of the way, but within easy access for tuning. Never drive and tune by yourself, always bring along a passenger if you are going to be making adjustments on the fly. If you choose a different mounting location, no problem, PowerCard is supplied with 10 feet of wire and its electronics are rubber encapsulated to keep them safe from vibration, moisture and debris.

Locating your factory ECU

We suggest connecting PowerCard's wires at the ECU for the cleanest installation. Mazda used 3 different ECU locations on the Miata. See Below.

90-93: The ECU is at the front of the passenger foot well on the floor. It has a metal cover over it that has 5 x 10mm bolts to remove it.

94-97: The ECU is located behind the passenger seat. It is mounted near the floor on the vertical part of the bulkhead leading from the floor to the rear deck.

99-02: The ECU is located above the clutch and brake pedals. To tight of an area to take a photo.

ECU Connections and Wire Colors

PowerCard is supplied with T-taps which crimp onto the wires. There is no need to cut and splice into the wire as we only need to get the signal, not interrupt it. In the following diagrams we will show the ECU connectors and call out the wires and their colors that you will be working with.

All Diagrams are viewed looking at the ECU with the harness clip at the top.

90-93 1.6L (click diagram to enlarge):

94-95 1.8L (click diagram to enlarge):

96-97 1.8L (click diagram to enlarge):

99-00 1.8L (click diagram to enlarge):

01-02 1.8L (click diagram to enlarge):

Initial PowerCard Settings:

The Miata can have a bit of a torque dip at mid-RPMs where the computer is right on the edge of going into open loop. This phenomenon is usually more noticeable in Miata's that have been modified with intake, header and exhaust. However, at higher RPMs, it actually needs less fuel. By raising the "High Load set point" (blue light at the right with a single red flashing) above where that torque dip takes place we were able to nearly eliminate that dip using the "transition fueling" adjustment. Then, since "High Load fueling" did not need to cover that torque dip, we lowered the fuel added in "High Load fueling" down to a much more optimum setting for the Miata at high-rpm in open loop. The car now "feels" smoother through the RPMs where the torque dip took place as well as stronger beyond it, but it required some retuning of the "transition fuel", "High Load fuel" and "High Load set point". Low Load Fuel is always indicated with Green, Transition Fuel with Amber and High Load with Red.

Cruise Fuel Added:
Once PowerCard initializes press the Mode button 1 time. This will be the Low Load Fuel Added mode. We suggest that initially the cruise fuel added stays at 0. Indicated by a fast flashing green light.

Transition Fuel Added:
Press the Mode button once and this will take you from Cruise Fuel Added to Acceleration Fuel Added. Transition fuel added should be set to 4 1/2. This is indicated by the 4 & 5 being illuminated in yellow.

High Load Fuel Added:
Press the Mode button once and this will take you from Transition Fuel Added to High Load Fuel Added. High Load Fuel Added should be set to 0 initially. This is indicated by a fast flashing red light.

Transition Set Points:
Low Load , Transition and High Load all have individual set points. The set point represents the load needed to activate the fuel added for that mode. We suggest setting all these set points to 4 1/2.

Now your Miata is ready for a test drive and fine tuning!