Megasquirt Terminology

This covers all of those abbreaviations used in megasquirt talk. TPS, MAP, and all that stuff!  

Here is some common terminology used in the Megasquirt Articles

CIS – this is the Bosch Continuous Injection System we are replacing. It works by a mechanical MAF sensor that opens a valve to inject fuel into the engine.

CPU – Central Processing Unit – refers to the Megasquirt chip itself

DB37 – This is the main 37 Pin connector on Megasquirt.

DB9 – this is the Serial communications and tuning port on Megasquirt. It is used for tuning, and is not used during normal running.

ECU – Engine Control unit – Many manufacturers call it an ECM – engine control Module, or PCM for Powertrain Control Module.

EFI – Electronic Fuel Injection

F_IDLE – this is Megasquirt terminology for the Fast Idle Solenoid, which boosts idle speed when the car has not warmed-up.

Hall Sender – The magnetic pickup used in VW distributors for RPM detection, there are 3 wires, power, Ground and the signal

MS – Shorthand for Megasquirt

Megasquirt I or MS1 – This refers to the 68HC908 CPU made my Motorola and flashed with Megasquirt I Code.

Megasquirt II or MS2 – This refers to the faster MC9S12C64 CPU made my Motorola and flashed with Megasquirt II code.

MSnS-e – Megasquirt ‘n Spark -Extra – this is special code for the Megasquirt I chip that extends it’s capabilities further, and gives it features comparable to the Megasquirt II chip.  This code does NOT work on a Megasquirt II chip though.  The code works with both versions of the PCB.

MT – Shorthand for Megatune

MegaLogViewer – this is a program that you use to analyze Megasquirt Logs taken in Megatune while driving the car. It can adjust your fuel maps based on oxygen sensor readings.

MegaTune – this is the program you install on your laptop to tune the Megasquirt ECU

PCB – Printed Circuit Board – this is the green board that is inside Megasquirt – there are currently two different versions. The V3 board is more robust and has many more built in options, but more expensive. The V2.2 board is inexpensive, and simpler than the V3

TPS – Throttle Position Sensor – it’s a 3 wire variable resistor mounted on the throttle plate to detect the position of the throttle.

USB Serial Adapter – This connects your tuning laptop to the Megasquirt unit. Most computers made after 1998 have USB ports.

V2.2 PCB – This is the earlier version of the Circuit board available. It does not have any advanced features, but it is simple and inexpensive.

V3 PCB – this is the later more advanced version of the circuit board. It adds flyback injector circuits to be able to run low impedance injectors like those available in the aftermarket, it adds more robust components and circuit protection, it has a 4 layer board that shields signals from external interference, it has a VR sensor circuit, a large heat sink, and best of all, a built in ignition coil driver. The disadvantage is that the board costs more, and is a lot more complicated to build.

V3.57 PCB – this is an advanced version of the V3 board that uses surface mounted components and is not generally available to DIY users. You can buy a pre-assembled one though.

Vref – this is the 5 volt reference signal that comes out of the Megasquirt. You can connect it to the TPS and the Hall Sender for power. It gives a VERY accurate regulated signal for Megasquirt to measure things by.