Megasquirt 2 Mod Kits

The 1.6L fuel pump

Wire your Purple Fuel Pump wire to 2O on your harness. This sends it to the AFM.

Jump the AFM connector like this:


This connects the Purple wire to the Fuel Pump Relay.

Fan Relay Control

If going standalone, you need to use MS to switch the fan on and off.

The easiest way to do this is using an existing circuit built in the MS, the Middle LED circuit. Since we don't install Q4, we can use that transistor to drive the circuit. The transistor that currently is in place is too weak to drive the relay.

Simply swap Q7 for Q4, and jump the flat side of the middle LED to your harness. That's it. Under the software you'll enable the middle LED circuit to use Output 4 and then turn output to drive the fan control.

After building the MS like outlines in Assembly - Standalone, you need to enable the output in Tunerstudio. Here is a screen shot to show you what to do:

If you followed the connection guide in the Assembly stage of this Wiki, your fan control output will be PM5 in your tuning software.


Electronic Boost Control

The built in boost control in MS2 is MUCH better than MS1, and very useful. I highly recommend it.


Mount the FET on the heatsink. Place the supplied insulator under the FET else it will cause the circuit to fail.

Top Leg: Goes to ground
Middle Leg: To harness (usally through the spare IAC outputs)
Bottom Leg: To JS11 through a 100ohm resistor

Jump the top and bottom leg with the 10K resistor

Solder the banded end of your diode to S12, and run it to the middle leg of the FET.


Boost Control Solenoid:

A source for it..


Purchase this solenoid to control your boost. Buy two 1/8" fittings to accept your vacuum lines.

To install:

Run your boost source off the turbo into the port labeled EXH. Run a line from the port labeled OUT to your wastegate.

Run one of the wires to a constant 12v source (most use the blue connector near the driver headlight). Run the other wire to your harness and back into the middle leg of the FET.

Tunerstudio Settings:

This is for a old GM boost control solenoid. If you have a newer one, your frequency and some other settings may be a little different


To Tune PID:

1. Set Integral and Differential Gains to 0% - To make tuning the Proportional gain easier, set the Integral and Differential gains to 0%.

2. Set Proportional gain to 150% and slowly lower - While tuning Proportional gain, higher numbers mean slower boost climb and lower final boost. For safety, start with a very high gain (150% should be sufficient). Find the RPM that typically spools quickly, and fully and quickly depress the accelerator. Note how much boost is reached. If boost overshoots the target, increase the Proportional gain. Otherwise, reduce the Proportional gain and try again. Do this until boost reaches the target with little or no overshoot.

3. Tune the Integral Gain - The next step after the target is reached consistently is to tune the Integral gain. Starting from the RPM used to tune the P-gain, fully depress the accelerator and watch the boost as the engine climbs through the RPM range. As the engine accelerates through the rev range, the boost will probably creep away from the target. Keep increasing the I gain until the controller adequately maintains the target with minimal oscillation.

4. Tune the Derivative Gain - If overshoot cannot be tuned out with the P gain on a quick acceleration, increase the D gain until the overshoot is minimized. Care must be taken when increasing the D gain as too much D gain can over-dampen the effects of the P and I gains.

Idle Control Mod

Idle Valve - DIYautotune

  • Mount your TIP120 to the heatsink, using a mica insulator and thermal grease under the transistor.
  • Connect pin 1 of the transistor to pin 2 of Q4, pin 2 to pin 3 of Q4 and pin 3 of the transistor to pin 1 of Q4
  • Refer to the posted picture to check that your pins are all jumpered correctly
  • Do not install Q20, R39 or D8
  • Jump R39 with a wire
  • Solder the banded end of your diode to S12, and connect the other end to the middle leg of the transistor. You can use one of the spare 1N4001s from D1 or D2
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