MegaSquirt
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MegaSquirt is an aftermarket electronic fuel injection (EFI) controller designed to be used with a wide range of internal combustion engines. It is an open source project headed by Bruce Bowling and Al Grippo, engineers that work on the U.S. East Coast. The project's do-it-yourself approach makes it the least-expensive system for this purpose. Basic costs can be below US$200 as of 2005, although this will vary widely depending on application.
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[edit] History
The EFI332 project started around 1995, and culminated in the release of about 200 kits in 2000. The system used a 32-bit MC68332 microcontroller from Motorola. A steep learning curve is believed to have prevented the system from gaining wider acceptance.[1] The MegaSquirt is considered to be the open source successor to the EFI332.
The two engineers decided to simplify the design and focus on managing the fuel injectors (the EFI332 could also control the spark plug ignition system if so desired). This was the basis for the first Open Source MegaSquirt.
[edit] Models
| MegaSquirt | MegaSquirt II | MicroSquirt | MegaSquirt-II Sequencer | |
|---|---|---|---|---|
| Released | 2001 | 2005 | 2007 | Not yet available |
| Processor | 8-Bit MC68HC908 | 16-bit MC9S12C64 | 16-bit MC9S12C64 | Dual 16-bit MC9S12C64 |
| Speed | 8 MHz | 24 MHz | 24 MHz | 2 x 24 MHz |
| Flash | 32 kB | 128 kB | 128 kB | 2 x 128 kB |
| User RAM | 512 B | 4 kB | 4 kB | 2 x 4 kB |
| Features | Depends on firmware, Inexpensive | Ignition Control, CAN Bus, GPIO, Inexpensive | Same Features as MS-II, plus Small Size, Sealed case, Dual Ignition/Injection Channels, Assembled | Sequential Injection (8 channels), COP (8-channels), individual trims, uses MS-II and MS-II Extra Firmware, Assembled |
[edit] Hardware
The assembled controller takes input from a few different sensors in order to manage the fuel injectors, including a throttle position sensor (TPS), exhaust gas oxygen sensor (EGO or O2 sensor), MAP sensor, intake air temperature sensor (IAT), and a coolant temperature sensor (CLT). The latter two sensors themselves are usually the General Motors type, although you can recalibrate the controller to use other sensors including Ford and Bosch.
As the project has gone through multiple hardware and firmware revisions, along with parallel projects that effectively "forked" the project and interlinked compatibilities, it is difficult to say with certainty which MegaSquirt is a specific version without knowing three things: microcontroller, printed circuit board and firmware versions.
[edit] Microcontroller
The version 1.0 MegaSquirt used an 8-bit Motorola MC68HC908 microcontroller, and all versions of the PCB support this processor. The later MegaSquirt-II upgrade includes a 16-bit MC9S12, and is considered an "intermediate" step from the original V1.01 and V2.2 MegaSquirt towards UltraMegaSquirt[2]
[edit] Printed Circuit Board
The first group buy of printed circuit boards was performed in 2001. These boards are considered V1.01, and are no longer available. The second group buy in 2002, as well as all following purchases until 2005 are considered V2.2, and have a V2.2 printed in the upper left corner of the PCB. Starting in July 2005, the V3 PCB was made available to use some of the advanced features of the MegaSquirt-II. As of Aug 2007, the v2.2 and v3 boards are still available.
There is a new version of the PCB. The V3.57 is a surface-mount device (SMD) version of the MegaSquirt V3 'thru-hole' main board. The 3.57 version of the board was created in order to allow for automated assembly of the majority of components using automated pick and place (machine assembly) and reflow soldering.
Although this board uses surface-mount components, the layout is the same as in the V3 main board. Component numbering remains the same in nearly all cases. In fact, this board version started with the V3 main board, and maintains the 4-layer construction and power distribution. It is the same size (4" x 6") and the connectors are in the same places, so it fits in the standard case with no modifications (though some modifications may be necessary for additional functionality).
Note that the V3.57 board is not a replacement for the 'build-it-yourself' boards, but rather an additional version of the MegaSquirt main board intended to make life easier for distributors who are building their boards for resale.
[edit] Firmware for MS1 chip
- standard V3.000 code
- This is the default pre-loaded code from Bowling and Grippo. It is a simple and effective fuel injection controller with an 8x8 fuel table for speed density or alpha-n. Narrowband or wideband oxygen sensors can be used for closed loop control and an on/off idle valve may be used.
- MegaSquirt 'n Spark-Extra (MS1/Extra)
- MegaSquirt 'n Spark-Extra is a firmware modification to the original Bowling and Grippo MegaSquirt written by Philip Ringwood and James Murray (with contributions from many more). As the name implies it adds ignition management, as well as a large number of other features such as boost control, nitrous, fan control, programmeable outputs, water injection and more to MegaSquirt. Hardware modifications are required to run ignition and the learning curve is steeper than a fuel-only implementation, but many hundreds of users use the "MS1/Extra" firmware. The firmware is has been very actively developed and is now a stable alternative to the base MS code. Most Megasquirt distributors ship the MS1/Extra firmware as standard on MS1 boards. The firmware is designed to operate using either a supported ignition system, such as GM HEI, or Ford EDIS, or it can decode certain trigger wheel signals from crank/cam sensor pickups and run wasted spark or coil on plug.
[edit] Firmware for MS2 chip
- 'standard MS2 code'
- This is the default Al Grippo code that you can load to your chip.
MS2 has (multiple) 12x12 fuel and spark tables. Can control distributor or EDIS ignitions and decode many standard toothed wheels. Additional features includes X-Tau transient enrichment compensation (acceleration enrichment), enhanced closed-loop mixture control, injector test mode, etc See the Megamanual for download and documentation
- 'MS2/Extra code'
- This is an extension of the base code with enhanced wheel decoding, wasted spark, EAE and other features. It adds many of the MS1/Extra features to the MS2 chip along with a significant amount of new features. Code is free download for MS2 and variants.
The latest variant is the MS2 EXT (Extended)with built in expansion Module, allowing GPS/GPRS/GSM/Bluetooth giving compete comms. This hardware is under beta test, and not a Bowling & Grippo product. With e I/O it over comes some weaknesses of the original, and allows more DIY involvement.
[edit] MegaSquirt-based projects
- MS1/Extra[3]
- MS2/Extra[4]
- MegaSpark[5][6] - DIY Ignition Advance Controller & Data Logger (obsolete)
- MegaJolt[7] - concept
- VEMS[10]
