Megasquirt Introduction

   Megasquirt is a DIY ECU that uses a programmable chip to completely run your engine if you want it to.  When buying megasquirt from websites prebuilt or not, the Motorola chip that is at the heart of megasquirt is preprogrammed with a basic firmware so you can get a car running off the bat.  If you want more specific information, http://www.megasquirt.info/ has a great manual, I will try to make things less technical so those of you who are less techno-savvy may have an easier time understanding what exactly is going on.

   Megasquirt uses an algorithm that controls injector and ignition pulses based on a number of different inputs from sensors.  Megasquirt requires you to have a coolant temperature sensor (CLT), intake air temperature sensor (IAT), exhaust gas oxygen sensor (EGO or o2 sensor), throttle position sensor (TPS) and manifold absolute pressure sensor (MAP, which is included when you buy megasquirt).

   As I said before, the chip at the heart of megasquirt has an embedded code, we will refer to this as firmware.  This firmware is upgradeable/updatable.  The basic megasquirt firmware uses a volumetric efficiency (VE) table that has 8 cells by 8 cells for MAP and RPM.  This table is what you use to "tune" your car, MAP (measures pressure in kilo-Pascals or kPa) determines how much load is on the engine, and compares to what RPM you are at. Volumetric efficiency is the ratio of the amount of air actually fills the cylinder to the amount that would fill the cylinder in a static situation. The VE table is used in the equation to tell how much fuel the engine needs.  Upgrading to MSnS-Extra will allow you to use a 12x12 VE map, which allows for more fine tuning.  The -extra code will also allow you to have multiple inputs and outputs to control things such as spark, boost control, idle control, shift lights, the list goes on.

    I would highly suggest you upgrade the firmware to the highest beta version available (v025 in March 2006) and run MSnS-Extra so you can run a 12x12 VE table, and have various other features

   The coolant temp sensor (CLT) is used to tell how cold or hot the engine is, so while warming up, megasquirt can give the engine more or less fuel.  When warming up, a car needs extra fuel to keep running, however it will die if it is too rich, or too lean.  The intake air temp (IAT) is used in the fueling code as well to calculate how much fuel your engine needs.

  The exhaust gas oxygen (EGO) sensor is not necessarily needed to run megasquirt, but will definitely help gas milage and helps fine-tune while driving.  If you use a wideband o2 sensor, you will be able to tune your car by yourself, instead of going to the dyno and using theirs to tune your car.  Innovate has a very good wideband sensor that connects to Megasquirt, and you can use it to tune your car.