The MegaSquirt fuel tuner is a build it yourself ECU. It takes some skill to do this, but look at the information below. You may find you CAN do this yourself.
Understanding how MegaSquirt controls the fuel injectors will help you to assemble, test, and tune your MegaSquirt for best performance. MegaSquirt works on a number of levels to inject the correct amount of fuel into your engine. Most tangible is the hardware. This consists of:
CPU (U1, the 68HC908) and clock section (Y1, the 32768 Hz crystal), that perform computations,
Serial communications section (most notably U6, the MAX232 chip) to enable tuning software to read and write parameters to MegaSquirt,
Power section (especially U5, the LM2937 voltage regulator) to provide a constant 5 volts for many of the other components,
Various input conditioning circuits (consisting mainly of capacitors, resistors, and diodes, but also including: U3, the MPX4250 MAP sensor, and U4, the opto-isolator for the ignition signal, and
A number of outputs to drive the injectors, relays, and LEDs. Significant components include U7, the 34151 FET injector driver, Q2 and Q7, the two IFRIZ34N FETs (field effect transistors) for the injector banks, Q1, the TIP32C flyback transistor, and a number of other transistor, capacitors, and resistors.
There are also a number of other associated parts, such as connectors, the case, cables, etc.
The MC68HC908 CPU is controlled by “embedded software”. This is “burned” into the non-volatile memory (remembers data even when the power is turned off) of the CPU. It is written in assembly language. The embedded code and its variants are freely available. Another part of the CPU memory is burned with the “bootloader”, which tells the CPU how to interpret and store new versions of the embedded code sent through the serial communications port. The parameters that adjust the embedded code to your specific vehicle are configured using a laptop and tuning software, such as MegaTune. These are Windows9x/Me/XP applications. They can read information coming from the MegaSquirt, as well as send parameters to MegaSquirt for use and storage.
The amount of fuel injected by MegaSquirt depends on several factors:
The Ideal Gas Law that relates the amount of air to its pressure, volume and temperature, (this is a fundamental part of the embedded code).
Measured values: manifold pressure, engine and intake air temperature, rpm, etc. (these are taken from the sensor measurements).
Tuning parameters: REQ_FUEL, volumetric efficiency, injector open time, etc. (these are input and adjusted using the tuning software).
MegaSquirt uses all these factors to determine the fuel pulse width - longer pulse widths mean more fuel (richer), shorter pulse widths mean less fuel (leaner).
More information can be found at MegaSquirt.
Spectre eMS-Pro Standalone
Based on the MegaSquirt-N-Spark Extra code, but taken 'to the next level' in nearly every way possible, the Spectre eMS-Pro is not really playing in the same court as some of our traditional more DIY oriented products. With roots firmly set in MegaSquirt technology, Spectre has stopped at nothing to add just about every 'extra' feature they could pack in the case. They started by changing the connector used to a heavy-duty Amp-Seal connector rated for automotive use, good move. Next they incorporated separate power regulators for the mission-critical and non-mission critical functions, keeping anything that could interfere with the running of your engine, but was absolutely critical, isolated and in its own safe little sandbox. Next Spectre added USB connectivity, you read that right.... the serial interface is still there if you want it, they simply ADDED USB, you can actually use both at the same time, potentially to allow datalogging (read only) on the serial, while tuning on the USB, or vice-versa.
External DIP switches to configure spark inputs and outputs
Nitrous Oxide Control
Knock Sensor Input (tunable to OEM sensors)
2-step launch control
Shift Light output
Cooling fan control
4-bar MAP sensor for up to 44psi of BOOST!
Second barometric pressure sensor for automatic baro correction
Fast-idle warm up or closed loop idle control via a PWM idle valve
Support for high or low impedance injectors
Support for single crank angle sensor or dual crank/cam sensor ignition setups
And plenty more... these are just the highlights!
AEM Universal EMS
AEM’s Universal Programmable Engine Management System adapts to any vehicle using the company’s flying lead wiring harness and sensors (sold separately). In addition to the features found in our Plug & Play EMS, AEM’s Universal EMS also includes 10 independent, built-in peak & hold injector driver channels, direct drive ignition and dual wideband UEGO controllers. Peak & Hold injector drivers enable users to utilize low impedance injectors with a true 4/1 Peak & Hold injector drive circuit. The Direct Drive ignition feature allows users to drive a coil directly from the ECU without the need for an igniter or ignition module, and a wideband UEGO controller is an essential tuning tool that provides a 0-5 signal for monitoring and tuning air/fuel ratios (AFR) on heavily modified high-performance engines.
System is fully enabled—Never pay for upgrades!
Runs on Windows™ compatible software
Live help window eases tuning process
Free software updates on aempower.com
Fuel table automapping
Programmable traction control
Onboard 512kb datalogger
Up to 10 cylinder sequential fuel injection
10 independent peak & hold injector drivers
Direct drive ignition feature eliminates need for igniter or ignition module
On-board wideband UEGO controller
6 general-purpose outputs
7 definable switch inputs
Electronic boost control
Soft cut rev limiters
Two step launch control
Wet or dry nitrous control
Definable knock control
Full idle control
4 EGT inputs with fuel control
16/32 hybrid high speed processor