Standalone Engine Management SEM301 Based on MS3x

$USD 345.0

SKU: sem301 Category:


Standalone engine management system based on Megasquirt MS3x Processor and firmware with enhanced inputs and output ports in sealed enclosure and sealed automotive connector. It is capable of controlling sequential injection on engines up to 8 cylinders, or semi-sequential up to 16 cylinders, combined with direct fire ignition for engines up to 8 cylinders or wasted spark ignition on engines up to 16 cylinders. Can be connected as fully standalone ECU or as piggyback and share the sensor reading with the stock ECU as it has differential trigger inputs, The 4 bar internal MAP sensor can read up to 44psi of boost, 2 Programmable knocking detector circuit can be used to adjust the ignition timing,  5V ref voltage, and internal switch to pull up resistor.  It has dedicated inputs (Crank, CAM, CLT, IAT, MAP, TPS, O2 and knocking) and 16 low side outputs to drive injectors or any solenoid valve. 4 dedicated ignition outputs and 4 ignition outputs shared with inputs. 9 digital inputs 5 of them can be used as analog or digital. It comes with 1.4 meter harness. Bluetooth as optional connectivity , SD card logging, Real time clock.


  • 2x Deffrential Trigger inputs (Hall, VR and Opto).
  • 16x High impedance low side output  3A each to drive injectors or to be used for auxiliary outputs.
  • 8x Ignition output 1A max (5V or 12V)/ 4 of them shared with inputs
  • 5x Inputs can be used as analog or digital input.
  • 1x Digital inputs one of them differential.
  • 4x dedicated analog input, coolant temperature, Intake air temperature,  O2 sensor, Throttle position.
  • 2x Programmable knocking input ./ shared with analog input.
  • 4 bar built in MAP sensor.
  • Fully compatible with MSextra Software
  • Fuel Table 16×16
  • Ignition Table 16×16
  • Connected to computer through USB.
  • USB cable
  • 1.4 meter harness + connectors
  • Supports CAN Bus
  • Bluetooth connectivity.
  • SD card logging.
  • Real Time Clock with backup battery
  • Can be connected as standalone or piggyback


Fuel table size 16×16
Fuel table resolution 0.10%
rpm resolution 1 rpm
Accel enrichment Simple (TPS,MAP), Enhanced (wall-wetting)
Spark table size 16×16
Advance resolution (commanded) 0.1 deg
Injector phasing Bank/batch fire
Fully sequential (up to 8cyl)
Injector timing Timed for start, middle, end of injection pulse
Injector trim Mapped trim table per cylinder.
Spark trim Mapped trim table per cylinder
Distributor spark Y
Trigger return dizzy Y
Simple wheel decoding Y
Every tooth wheel decoding Y
Wasted spark Y
Coil on plug Y
Dual dizzy Y
Cam / 2nd tach input Y
Number of spark outputs 8
Rotary trailing Y
HEI7, GMDIS Y (with bypass control)
Oddfire wheel decoder Y
Oddfire dizzy Y
Neon/420A Y
36-1+1 Y
36-2-2-2 Y
Subaru 6/7 Y
IAW Weber-Marelli Y
Mitsubushi 6g72 Y
4/1 CAS Y
4G63 (Miata) Y
99-00 Miata Y
Renix 44-2-2 Y
Twin trigger (aka. dual spark) Y
Suzuki Swift Y
Suzuki Vitara Y
Daihatsu 3 cyl Y
Daihatsu 4cyl Y
Rover K Series 36-1-1 Y
Rover K Series 36-1-1-1-1 Y
Rover K Series 36-2-2 Y
Honda VTR1000 12-3 Y
Chrysler 2.2/2.5 Y
GM 7X native Y
Nissan 360 tooth CAS SR20, RB25
Load methods SD, AN, map/baro (load%), MAF, ITB
Load blending Y
Load tables 2
Staged injection Y
Includes sequential staging and multiple banks.
Over-run fuel cut Y
Tachometer output Y
Launch Control/flat shift Y
Spark cut rev limit Y
Dwell duty% Y
Dwell battery correction table of %ages
Cranking pulsewidth table of %ages
Alternate cranking injection Y
Specific cranking advance, dwell Y
Fixed timing for setup Y
Test mode Pump, Inj, Coils, Idle
Closed loop idle control Y
Boost control Y (open or closed loop with PID control)
Nitrous control Y (2 stage progressive)
Knock sensor (software) Y
Realtime barometric correction Y
Water Injection Y
Table Switching Y
Configurable outputs Y
AFR target tables Y
Dual fuel tables (per bank) Y
Synchronous sensor sampling Y
CAN communications Y
Built in tooth/trigger loggers Y (tooth, trigger, composite, sync-errror)


About the author


  1. I want to use this for a fuel only setup. I was going to use tach signal to trigger it. This will be setup as a piggyback. I currently have a tach signal but how would this be wired to accept 1 wire tach signal.

      1. My buddy ordered it for me. Name should be Chris. If the harness is extra i will gladly purchase it.

        1. it depends on your order, can you send me photo of invoice, then i can tell if it is with harness or not and how to add it if you ordered without.

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