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These are the parts needed for the 'TIP120 PWM IAC' mod as described in the blue box after step 62 of the MS v3 Assembly Guide. This mod supercedes the previous 'mk-FordIAC' as it's more robust since it allows you to heatsink the transistor. If you are installing all optional components on the v3 heatsink (leaving no extra space for this transistor there) then you can drill a hole in your case and use it as your heatsink.
This kit will work with both the V2.2 and V3.0 PCBs. (Not needed on PCB 3.57 SMT ECUs)
V3.0 Installation
From the blue box after step 62 of the MS v3 Assembly Guide:
DO NOT install Q4 for use with PWM idle valves - it cannot handle the current directly for PWM idle valves. ('On/Off' type idle valves used with a relay are fine with the default Q4.)
Instead, for a PWM idle valve, use a TIP120/121/122 transistor (included in this kit) mounted on either the heat sink (if you have a spare spot) or the case. You should use a mica insulator with heat sink grease (both also included) as well. Run wires to the Q4 connections as shown below:
Do not install Q20 or D8, and jumper R39 as well. You will also have to put a 1N4001 diode (included) across the PWM Idle valve itself - the banded end goes to the 12 Volt supply, the non-banded end goes to the lead that goes to MegaSquirt (this diode is for flyback purposes on the idle valve).
V2.2 Installation
Replace transistor Q5 with the TIP120/121/122 transistor. You should mount the transistor to the case using the included mica insulator and heat sink grease. Wire it to the board as shown:
You do not need any further modifications to the board or external wiring when installing this with a V2.2 board. (Ignore the line about Q20, D8 and R39 in the image above, that applies to V3.0 boards only)
Wiring and Configuration
To wire this up without the relay board (directly to the ECU), wire up the hot wire from the idle valve to switched 12v+, and wire the negative wire from the idle valve directly to pin 30 on the MegaSquirt DB37.
To wire this up with the relay board, you will need to jumper the FIDLE relay to take it out of the loop; below is a picture of how to do this. Then you will still wire up the hot wire from the idle valve to switched 12v+ (you could use the fuel pump power from the relay board), and wire the negative wire from the idle valve directly to the FIDLE terminal on the relay board. This will allow full control of your PWM idle valve.
Image 'borrowed' from the MSnS-E pages
Configuration with the MS-I and MSNS-E firmware
For tuning the PWM Idle using the MSnS-E firmware the information is located in the MS1/Extra Manual on the Idle Valves page.
Configuration with the MS-II
For usage with the MS-II you first use the MegaTune Configurator, and open CAR1>SETTINGS.INI>SETTINGS>IDLE_CONTROLLER and select PWM_GAUGE from the dropdown box at the top right.
Then save and exit the Configurator.
Open MegaTune and connect to the ECU, and from the SETTINGS menu choose IDLE CONTROL. Select the PWM Warmup ‘Algorithm’ and then you can configure the values for your vehicle and click ‘Burn to ECU’.
More information on tuning these settings can be found here: http://www.megamanual.com/megatune.htm#sd
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