Megasquirt-3 MS3 Ignition - LS1 (24X)

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GM LS1 and family 24X reluctor engines.

The MS3+MS3X can easily interface with stock LS1 crank and cam sensors, high impedance injectors and standard logic coils.

Crank and cam sensor inputs
These sensors need +12V, ground and supply a 'clean' logic signal for the Megasquirt. The Megasquirt will need setting internally for the 'VR' circuit and set to accept a LS1 input without a pullup.
(If you have a DIY V3.0 mainboard ensure that U7 is not an LM2904 as it will almost certainly cause problems with the LS1 24X wheel. It needs to be MC33072 or TLC2272AIP or MCP6002-I/P)
See the Tach input sections

  • Crank input on V3 board
  • Crank input on V3.57 board
  • Cam input on MS3X

    See the wiring diagrams page for the main plug and stepper idle wiring.
    V3 LS wiring
    Looom colours taken from one engine loom, may vary.
    LS crank/cam sensor wiring


    General layout of ignition and injector wiring:

    LS1 coil wiring
    GM LS1 coil wiring
    A dwell figure of 4.0ms is advised for LS1 coils.(was 4.5)
    Note that some coils have a built-in overdwell protection feature. If given too much dwell the coil will automatically spark. This can give a dangerous advanced spark. Be sure to strobe your timing at high revs to ensure this is not happening.

    LS2 coil wiring
    GM LS2 coil wiring
    A dwell figure of 4.0ms is advised for LS2 coils.(was 4.5)
    Note that some coils have a built-in overdwell protection feature. If given too much dwell the coil will automatically spark. This can give a dangerous advanced spark. Be sure to strobe your timing at high revs to ensure this is not happening.

    See also the general documentation on Ignition outputs and Injector wiring

    Settings

    On 'Engine and Sequential settings' set Main Fuel outputs to MS3X fuel and enable fully sequential.

    On 'Ignition Options and Wheeldecoder' set Spark mode to LS1, input capture to 'Rising Edge', Spark output to 'Going high (inverted)', coils to 'Coil on Plug', spark hardware to 'MS3X spark', Cam input to 'MS3X Cam in'
    ls1 settings

    If you have a question, comment, or suggestion for this FAQ please post it on the forum.

    No part of this manual may be reproduced or changed without written permission from James Murray, Ken Culver and Philip Ringwood.