MJLJ V3 Operation Guide
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- 1 First time use
- 2 Connecting to the MJLJ
- 3 At a glance: Main Screen
- 4 Working with the Ignition Configuration
- 4.1 Retrieving the Ignition Configuration
- 4.2 Ignition Map
- 4.3 Editing Ignition Map
- 4.4 Controller Options
- 5 Writing the Ignition Configuration
- 6 Additional Options
- 7 Tuning your Ignition Controller
- 8 Advanced Topics
First time use
Installing Configuration Software
Download the version of the Configuration software that matches your controller firmware. It's likely you have a very recent firmware image, so start by downloading the latest version of the Configuration software.
Setting the Serial Port
Find and run the Configuration software by finding the icon under the Start Menu program group. Once the program is running, you can set the serial port the MJLJ is connected to by clicking Tools/Configurator Options.
If you don't know which COM port you have the MJLJ connected to, you can discover this under Windows Device Manager: Find the 'My Computer' icon, right-click and select Properties. From this window you will be able to access Device Manager.
Expand the 'Ports (COM & LPT)' to see the list of installed COM ports.
Once you're certain which COM port you're using for the MJLJ, select this value in the options dialog.
Configuring MAP or TPS
In the Controller Options dialog, select the Load type you have for your MJLJ- Throttle Position sensor(TPS) or Manifold Absolute Pressure (MAP).
Configuring Normally Aspirated or Forced Induction
Check the 'Normally Aspirated' box if that matches your engine type. This setting will scale the load axis for the runtime and logging views to 103KPa maximum.
Otherwise, leave the box clear if your engine is turbocharged or supercharged. This will set the maximum scale to 255 KPa (approximately 21 PSI of boost)
Connecting to the MJLJ
After setting the COM port, connect the serial cable to the MJLJ and apply power. If you already have the MJLJ wired into your engine's wiring harness, turn the ignition key to 'on'. If you are testing the MJLJ on the bench, you can simply power the unit with a 9V battery or a suitable 9-15V power supply.
The first way to verify connectivity is to observe runtime data on the screen. On a running engine you'll see the real-time RPM, load and ignition advance values on the gauges at the bottom of the window.
If you're testing on the bench or on a non-running engine, you will still be able to observe some runtime activity by simulating load changing on the engine. For TPS- move the accelerator pedal; MAP- you can manually apply pressure or vacuum.
Common connection problems
If the Configuration Software cannot connect to the MJLJ, you will see one of the following messages in the status bar:
Timeout reading runtime data
The Configuration Software did not get a response from the MJLJ on the serial port you specified.
- Does the MJLJ have power, and connected to the computer with a standard serial cable or compatible USB-Serial adapter?
Could not open port
The Configuration Software could not access the serial port you specified.
- The port is invalid: Check Device Manager for the proper serial port.
- Serial port in use: If another program is using the same serial port your computer will block the Configuration software from accessing the serial port. Check that you don't have any other software which may open and use the serial port you're trying to use, such as PDA sync software.
At a glance: Main Screen
The runtime gauges show the current engine parameters.
This is the actual ignition advance calculated and commanded to the EDIS module. This value should correspond to direct measurement of ignition advance, e.g. observation with a timing light.
This shows the Engine's RPM. The yellow and red regions reflect the current rev limiter setting. The yellow region marks the soft-rev limit region; the red marks when the Hard Rev Limit output is enabled.
The load gauge shows either KPa or TPS %, depending on your Controller's configuration and Configuration software setting. For MAP sensor based MJLJ's the scale can be further adjusted to show 0-103 KPa for normally aspirated engines. With forced induction applications the gauge can be set to show the full 0-255KPa range supported by the on-board MAP sensor.
Working with the Ignition Configuration
Retrieving the Ignition Configuration
The ignition map organized as a 10 x 10 grid of ignition advance values, with Load/RPM bins defining the steps between grid values.
- Load Axis: The Load axis is is represented vertically, from low engine load at the top to high engine load at the bottom.
- RPM Axis: The RPM axis is represented horizontally, from low RPM on the left to high RPM on the right.
- Bins: The steps between engine load and RPM points are defined as 'Bins'- these are the values shown along the borders of the Ignition Map grid.
- Ignition Advance: Each cell in the grid represents an ignition advance value, in actual degrees before top dead center (BTDC).
Editing Ignition Map
Adjusting ignition advance
- Changing single value
- Changing multiple cells
To change multiple cells at once, select a region of cells much like you would with a spreadsheet program. You can select contiguous regions by clicking and dragging, or select individual cells cells by holding down the control key while clicking.
- Ignition Advance range: Allowable ignition advance range is 0 to 59 degrees BTDC.
Adjusting Load / RPM Bins
To change the Load or RPM bins perform one of the following:
- Click the 'Edit' menu and select'Edit RPM and Load bins'
- Ctrl-B in the main window
- Right click on the Load or RPM bins in the grid and select 'Edit RPM and Load Bins'
Edit the values and click 'OK' to confirm your changes.
To access the various MJLJ controller options, click the 'Options' tab below the ignition grid.
Select the number of cylinders for your engine (4,6 or 8 cylinders), matching the EDIS module you are using.
User Configurable Outputs
The Megajolt Lite Jr. offers four identical configurable outputs, each with customizable activation.
- Load: Select this type to activate on a Load threshold.
- RPM: Select this type to activate on an RPM threshold.
- Normal: The output will be enabled at or above the set activation point and disabled below set activation point.
- Invert: The output will be disabled at or above the set activation point and enabled below the activation point.
The Activation point sets the RPM or Load threshold for triggering the output.
Hysteresis on outputs
- RPM configured outputs: Hysteresis is set at 100RPMs.
- Load configured outputs: Hysteresis is set at 1 load unit (MAP KPa or TPS %).
For wiring instructions on the User Configurable Outputs, see the Installation Guide.
The Shift Light output is activated when engine RPM reaches the configured threshold. Typically this output would be used to illuminate a dashboard-mounted light. For shift light wiring instructions, see the Installation Guide.
The Rev Limit output is an RPM switch with special behavior.
- At the specified RPM threshold, the Rev Limit output is activated and can be used to trigger an external Rev Limiter module, such as the Autosport Labs Hard Rev Limiter
- 100 RPMs before threshold the ignition advance goes to zero BTDC to act as a 'soft' rev limiter by significantly reducing engine power. Together with an external hard rev limit module this provides an effective rev-limit solution, naturally excluding mechanical over-rev situations.
For instructions on wiring an external rev limit module, see the Installation Guide.
Writing the Ignition Configuration
After editing the ignition map or controller options, you may write the changes to the controller. To do this, click the Write Ignition Configuration toolbar icon to write your changes to the controller.
These changes are made to the Controller's RAM memory, which is used for the actual runtime operation. Therefore, the changes you make may reflect in the engine's operation. For example, if you are tuning the idle region and you alter ignition advance values in map where the engine is idling, you should observe a change in the engine's behavior once you write the configuration to the controller.
Important Note: Writing the ignition configuration only updates the Controller's RAM. If changes are not persisted to the controller's Flash memory, the changes will be lost if the controller loses power (e.g. ignition key turned to 'off') This behavior is by design. Persisting the data to flash requires a significant amount of time and momentarily pauses the controller's operation while the flash memory is written.
Commit to Flash
To make the changes permanent in the Controller's flash memory, Click the 'Commit configuration to Flash' toolbar icon . The controller will write the configuration to flash memory, and changes will be preserved after the controller loses power.
Load Axis Calibration
If you have a TPS-optioned MJLJ, you can calibrate the Load axis to reflect actual throttle opening percentage.
With the MJLJ powered up, click the 'Tools' menu and select 'Load Axis Calibration'. You will see the Load Axis Calibration dialog.
Guided TPS calibration
To calibrate your Throttle Position Sensor, click the 'Calibrate TPS' button on the screen and follow the on-screen prompts.
This guided process reads the closed and open throttle position, generates a new load axis table and Flashes the new table to the controller. Once this is performed, it should not require additional changes unless the throttle linkage or sensor is adjusted or modified.
Aside from calibrating a TPS-optioned MJLJ, you can also directly edit the load-axis calibration data. For example, if you're using a non-standard external MAP sensor you can load the sensor's voltage curve using this tool.
Load / Save calibration
You can load and save the Load axis calibration data using the 'Load Calibration' / 'Save Calibration' buttons. The file is in plain text format of 256 values, with the file's line number representing the ADC voltage (line 0 = 0v; line 255=5.0v; linear scale).
The value on each line maps the ADC voltage to the desired load in KPa or TPS %.
The Load calibration data can be retrieved, inspected and modified directly using 'Read Calibration' / 'Write Calibration' buttons under the 'Edit Values' section.