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MJLJ design and architecture

Design Goal

The goal of the MegaJolt Lite Jr. was to design a cost-effective, yet sufficiently capable ignition system that works in conjunction with the Ford EDIS ignition module.

With the MJLJ and EDIS module working together as a unit, the result is compelling: A fully mappable, crank-fired, stand-alone ignition system, achieving or exceeding the capabilities of other systems that cost up to 10x as much to implement.

Features

Current Features

  • 10 x 10 ignition map, with full linear interpolation between values
  • Load axis calibrated by on-board Manifold Pressure (MAP) sensor or external Throttle Position Sensor (TPS)
  • Four user-defined output switches, which trigger on RPM or load
  • 'Shift light' output- for driving a dash-mounted shift light
  • External Rev-Limit trigger output (The Ford EDIS module has no 'rev limit' signal, so an external circuit to cut power to the ignition coil is required)
  • Modern, easy to use, and customizable Windows-based configuration software
    • Load, configure and save Ignition Configuration
    • View, log and interact with engine runtime data
    • Interactively visualize and tune ignition map

New with V2.7.x/V3.1.0 beta

  • Dual, on-the-fly switchable ignition configuration
  • TPS / Load axis calibration
  • Improved user outputs with hysteresis
  • Configurable cranking RPM advance


Limitations

To keep cost and complexity down, certain features have been omitted:

  • Knock sensing
  • Engine temperature compensation (for warm up mode)

All of these features are candidates for upcoming versions of the MJLJ.

System Design

MJLJ - EDIS relationship
MegaJolt Lite Jr Ford EDIS module
Controls Ignition Advance Drives ignition coils


During engine operation, the EDIS module queries the engine management system for the appropriate ignition advance. This signal communicated on the SAW port of the EDIS module. The engine management system in turn calculates the ignition advance based on the current operating conditions, and communicates a response back on the PIP port of the EDIS module. See Ford EDIS technical information for more details.

The MegaJolt Lite Jr. acts as a proxy for the normal Ford ignition system. When the MJLJ receives the SAW pulse it calculates the ignition advance by measuring RPM and load and finds up the appropriate advance value which was set by the end-user. Once the advance is calculated, it replies with the appropriate message on the PIP port of the EDIS module. This request - reply process occurs on each ignition event while the engine is running.