MegaSquirtPNP
Plug-N-Play Standalone Engine Management System
by DIYAutoTune.com


MegaSquirt PNP Gen2 Documentation

Model/Vehicle Specific information for model MSPNP2-NS8994 on a '91-'94 240SX Nissan Sentra or NX2000 / NX1600

Please read all documentation before installing your MegaSquirtPNP EMS, and verify you've followed all steps before starting your engine for the first time.

Physical Installation

These cars have the ECU at the bottom of the console stack.  To access it, there's a pair of panels you'll need to remove on the floor board in front of the center console, one on each side.  Next, there's a bracket holding the wiring harness to the car body that you'll need to remove.  Unbolt the ECU, lift it out, and unscrew the bolt in the center of the wiring connector to remove the wiring harness.  Bolt the wiring harness connector to the MSPNP and secure the MSPNP to the floor with the included sheet metal screws.  Note that the wiring harness connector must be bolted down tightly for the connector to work - often a bit tighter than you can get with a nut driver, so you will need a wrench to handle for this. Finger tight is asking for trouble.

B13 chassis Nissan ECU location

You'll need to hook up the MSPNP's built in MAP sensor.  Cut the vacuum line at the fuel pressure regulator and insert the included tee fitting.  Run the vacuum line from this tee through a grommet in the firewall and to the barb on the back of the MSPNP.

We also recommend routing the tuning cable from the ECU to a location on the console of the passenger compartment, somewhere where you can easily tuck it away when not in use.

At this point, it is safe to power the ECU up, but please make sure you load the appropriate startup map for your specific engine before attempting to start the vehicle.  Using the wrong startup map may result in a no-start condition, or even engine damage if the engine is driven hard before the correct map is loaded.

Verifying and Adjusting Base Timing

Once the MSPNP is installed, it is mandatory to check timing on all NS8994 applications. First, put the MSPNP in fixed timing mode by going to Ignition Settings -> Ignition Options/Decoder Wheel (For v1.2 MSPNP2s, go to Basic Setup -> More Ignition Settings). Set Fixed Advance to "Fixed Timing", set Timing for Fixed Advance to 15 degrees, and click the Burn button.  

While you can adjust the timing in the same manner as with a stock ECU by adjusting the distributor, MSPNP gives you another option: adjust the trigger angle with TunerStudio under the spark settings. Increase the trigger angle to retard the spark, or decrease it to advance the spark. Adjust the number until the timing is at 10 degrees.  MSPNP requires a trigger angle of at least 50 degrees on this unit to obtain full spark advance.  

GA16 distributor

If you adjust the distributor for adjusting the timing advance, set the trigger angle to default value of 120 degrees in TunerStudio and turn the distributor until the timing is at a steady 15 degrees BTDC, then lock the cam angle sensor back down there and check the timing with the light to make sure the distributor didn't slip. If you run out of adjustment, use the trigger angle setting in TunerStudio to get the correct timing.

The timing marks are on the front of the engine, to the left of the engine compartment. It's easiest to view from standing in front of the grille.  There is a white mark at 15 degrees that you need to line up with the pointer. Once you have adjusted the trigger angle and/or cam angle sensor to get 10 degrees BTDC, turn off the fixed timing mode by changing the Fixed Timing setting to "Use Table." 

GA16DE timing marks

 

Intake Air Temperature Sensors, and Removing the Mass Air Flow Sensor

These cars do not have an intake air temperature sensor. We strongly recommend installing a GM IAT sensor in order to allow the ECU to correct for air temperature variations.  The best location for an IAT sensor is just upstream of the throttle body.  There are two points on the MSPNP where you can connect an IAT sensor.   If racing class rules do not permit you to remove or even unplug the mass air flow sensor, you may wire the IAT to pins 10 and 15 on the 15-pin option connector on the v1.2 board and pins 20 and 22 on 26-pin option connector on the v1.3 board.

For most users, you'll want to unplug the MAF and connect the IAT sensor to the pins corresponding to the white and orange wires (orange/purple and white for SE-R users) on pins "B" and "C" of the mass air flow sensor.  You can use the pins in our IAT sensor kit, plugged into the MAF connector, and fold over and secure with high temperature tape.  3M makes tape, such as Super88, that can handle the temps found in engine bays.

If you are wiring the IAT sensor in through the MAF connector, it is necessary to modify a jumper inside the MSPNP.  Remove the lid and find 3 pin header on the lowest board labeled "Pin 16 input". Pull the connecting jumper off this header and place it on the center pin and the rightmost pin, marked "AT".

 

After installing the IAT, turn the ignition key on but do not start the engine. Connect to the MSPNP with TunerStudio. Go to the Tools menu and select Calibrate Thermistor Tables, select Air Temperature Sensor, and select GM from the Common Sensor Values drop down box.  Leave the bias resistor setting at 2490.0 ohms.  Click Write to Controller.  This will update the sensor calibration in the MSPNP.

Once you have an IAT sensor in place, you can remove the MAF and replace it with a length of straight pipe for a less restrictive intake.

Note: If you are using the MSPNP with a turbo or supercharger:

After you remove the AFM, install the IAT sensor in the location pictured above which is just before the throttle body inlet.  The IAT needs to measure the air temperature as it's entering the engine, not the ambient air temperature in the engine bay.  Only by placing the IAT just before the throttle body can an accurate air temperature measurement be taken AFTER the compressor has heated the air and the intercooler has cooled it.  Accurate air temperature measurements are needed for proper fueling and ignition advance calculations.

Fan Control

Your MSPNP is set up to use the PM5 - Warm-up LED output for fan control, under Extended -> Output Port Settings.  The fan will come on whenever this output is on.

Alternate Distributor Trigger Disc and Sequential Injection

We've created a bolt in trigger disc as an optional mod you can install with the MSPNP (not included). This trigger disc has a pattern that works better with MS2, allowing more precise timing control, sequential injection, and distributorless ignition conversions.  It bolts right into the stock distributor with no cutting or rewiring required (unless you change to distributorless ignition).  This trigger disc is available in two sizes to accommodate different models.  These motors need a 50 mm disc (Part No. TW_SR20).

To install, simply remove the distributor cap and rotor. There's a single Philips head screw that holds the trigger disc and its mounting plate in place. Unscrew this, remove the disc and put ours in its place and bolt it back together. Our trigger discs are meant to be installed with the side shown below facing up as you look into the distributor; if they are installed upside down, you'll need to change the trigger angles in TunerStudio at the minimum.

50 mm trigger wheel (50 mm trigger wheel)

Once you have the disc installed, use these settings in TunerStudio:

  • Settings under Ignition Settings:
    • Spark mode: Toothed Wheel
    • Ignition input capture: Falling Edge
    • Spark output will depend on what output setup you're using. IGN-1As, LS coils, and QuadSparks all use Going High / Inverted. Getting this setting wrong can damage the ignition module and/or coils. If the ignition module or coils get hot with the key on and the engine off, turn the key off immediately and select the opposite output setting.
  • Settings under Ignition Settings:
    • Trigger wheel arrangement: Dual wheel with missing tooth
    • Trigger wheel teeth: 12
    • Missing Teeth: 1
    • Tooth #1 angle: 345 (This varies slightly between individual engines. Check with a timing light and adjust as needed.)
    • Wheel speed: Crank wheel
    • Second trigger active on: Rising edge

Because the distributor has some built in adjustment, it's likely that many installs may need as much as 20 degrees of adjustment to the Tooth #1 angle setting, so you will need to check your timing with a timing light. Treat these values as a starting point, not the definitive, final numbers.

If you are converting to distributorless ignition, you will also set the Number of Coils setting to Wasted Spark. This will let you use the spark outputs on the option connector.  Spark A fires cylinders 1 and 4, and spark B fires cylinders 2 and 3.  These signals may be wired directly to GM LS coils or DIYAutoTune.com's IGN-1A coils (each output will fire two coils), or other coils that take a 5 volt logic level trigger and have a built in ignition module.   Other coils will need an ignition module, such as DIYAutoTune.com's QuadSpark.

To enable sequential injection, go to the Advance menu, select Sequential Injection, and set Sequential Injection to "Sequential / Semi-Sequential." Click Burn, and turn the MSPNP off.  There are a couple jumpers that need to be adjusted inside the MSPNP before you turn it back on.  Take the MSPNP lid off, and place the J8 jumper (upper right hand corner) and the J10 jumper (upper left hand corner) both in the "4" (outermost) position. This will put the MSPNP hardware in sequential injection mode.

Sensor Calibration

If you need to recalibrate your temperature sensors, such as after loading firmware, here are the values to use for the stock sensors.  The bias resistor is 2490 ohms. Use this chart for the CLT sensor. 


  Temperature (degrees F) Temperature (degrees C) Resistance (Ohms)  
  68 20 2500  
  94 35 250  
  230 110 145  

Use this chart for the factory IAT sensor. GM IAT sensors can use the defaults in TunerStudio.


  Temperature (degrees F) Temperature (degrees C) Resistance (Ohms)  
  14 -10 9000  
  68 20 2500  
  122 50 820  


 

The MegaSquirtPNP, as with any programmable engine management system, may not
be legal for use on pollution controlled vehicles and is therefore produced and sold for off road/race use only. Check federal/local laws.

MegaSquirtPNP, MSPNP, MegaSquirt PNP, and MS PNP, are trademarks of Hoffmann Innovations, Inc d/b/a DIYAutoTune.com.