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This is the index to the latest web-based version of the manual for the MegaSquirt® EFI Controllers. This index and the manual is for Bowling & Grippo code and hardware only. This manual is updated frequently, and contains the latest information on assembling, testing, troubleshooting, installing, and tuning your MegaSquirt® EFI Controller from Bowling and Grippo.

For the MegaSquirt® Frequently Asked Questions and answers, click here.

MegaSquirt® and MicroSquirt® controllers are experimental devices intended for educational and research purposes. MegaSquirt® and MicroSquirt® controllers are not for sale or use on pollution controlled vehicles. Check the laws that apply in your locality to determine if using a MegaSquirt® or MicroSquirt® controller is legal for your application.

Quick Links

↓↓↓The links in the left column take you to the various sections of the manual, the links on the right take you to the specific subsections.↓↓↓

Introduction to the MegaSquirt® EFI Controller

Start here if you are new to MegaSquirt® EFI Controller, this contains important background information.

How the MegaSquirt® EFI Controller Works

This section contains fundamental information on how the MegaSquirt® EFI Controller works, and how it doesn't.

MegaSquirt-II™ Processor Upgrade

Here is information on the MegaSquirt-II upgrade daughter card.

MicroSquirt™ EFI Controller

Here is information on the MicroSquirt® EFI controllers.

MS-II Sequencer™ EFI Controller

Here are links to information regarding the MS-II Sequencer™ fully assembled ECU that can do sequential injection and individual cylinder fuel and spark trim.

The V3.0 MegaSquirt® Main Board

This section contains the information on the V3 main board.

MegaShift™ Transmission Controller Code

The MegaShift™ transmission controller code is for the GPIO board from B&G. This can control up to 8 forward speeds and eight shift solenoids (plus a 16x9 table for controlling a PWM line pressure valve). It has manual and fully automatic modes (16x9 load x speed table), with under and over rev-limit protection, 'paddle' shift buttons, and full data logging of all inputs and outputs (among many other abilities). See the Introduction for many more of MShift™'s functions.

The GPIO Board

This section contains the information on the CANbus network enabled GPIO (general purpose input/output) I/O extender board from Bowling and Grippo. Click here to purchase a GPIO kit

  • GPIO Board:
  • Applications:

    • V3.57 SMD Main Board

    Information about the V3.57 SMD 'pre-built' MegaSquirt® main board.

    Assembling Your v2.2 MegaSquirt® Main Board

    This section contains the v2.2 main board assembly guide and troubleshooting information.
    If your V2.2 main board is RED, your board is NOT a Bowling and Grippo main board, and these instructions DO NOT APPLY to your board. Ask your seller to exchange it for a genuine B&G board, or give your money back.

    Schematics & Troubleshooting

    Various MegaSquirt® schematics and other info for troubleshooting.

    Wiring and Sensors

    This section has information on external wiring and sensors for use with the MegaSquirt® EFI Controller. It is mostly for MS-I, for MS-II, also see the individual documents (above) for IAC, ignition, MAF, knock sensors, etc.

    Injectors & Fuel Supply

    This section contains information on selecting and using air and fuel supply components for use with the MegaSquirt® EFI Controller.

    Tuning Your MegaSquirt™ EFI Controller

    This section explains how to configure and tune MegaSquirt™ on your engine.
  • MS-II™ FUEL:
  • MS-II™ IGNITION:
  • MS-I™ (fuel only):

    • TunerStudioMS

    TunerStudio is Phil Tobin's version of a tuning application for MegaSquirt®. It provides the ability to configure and tune all MegaSquirt® controllers.

    The tuning parameters available depend on the code and the associated INI files (not the tuning software), so the same descriptions applies to all tuning softwares.

    Files

    This section has links to various code files, software, and documents in PDF format.

    MegaSquirt® Embedded Code

    Here are guides to writing, compiling, and loading embedded code to MegaSquirt®.

    Appendices

    Miscellaneous MegaSquirt® Information.

    Last Updated: 04/26/2025 23:22:23
    MegaSquirt® and MicroSquirt® controllers are experimental devices intended for educational purposes.
    MegaSquirt® and MicroSquirt® controllers are not for sale or use on pollution controlled vehicles. Check the laws that apply in your locality to determine if using a MegaSquirt® or MicroSquirt® controller is legal for your application.
    ©2004, 2014, 2022 Bruce Bowling and Al Grippo. All rights reserved. MegaSquirt® and MicroSquirt® are registered trademarks. This document is solely for the support of MegaSquirt® boards from Bowling and Grippo.