Q. What is MegaSquirt-II?

A. MegaSquirt-II is an "intermediate" step from the original V1 and V2.2 MegaSquirt^® towards UltraMegaSquirt. It is basically a plug-in processor card which has the MC9S12C64 processor plus support hardware as well as a stepper motor chip.

Q. Why would I want MegaSquirt-II?

A. MegaSquirt-II adds the following enhancements over MegaSquirt:

1) Processor: When MegaSquirt^® was started almost five years ago, the best bang for the money was the HC08 family (also Atmel and Microchip). In those five years, looking at the next step range of processors, the family that stands out is the HC12/HCS12.

Specification	MC68HC908 (MegaSquirt)	MC9S12C32 (MegaSquirt-II)
CPU core	8 bit	24 bit
Speed	8 MHz	24 MHz
Flash	32 Kbytes	64 Kbytes
User RAM	512 bytes	2K bytes

2) Existing software: The goal of choosing a processor is to try to keep the current established code operational. With the HC12 family, it is extremely easy to modify existing assembly code for this processor - it amounts to about a two hour effort, without taking advantage of the HC12 architecture. And, if people want to code in C, there is a good GNU port available, as well as Metrowerks Codewarrior.

3) 12 x 12 Tuning tables: for Volumetric Efficiency (VE) table, 12 x 12 for Air Fuel Ratio (AFR) table, and 12 x 12 for Spark Advance table. There are separate AFR and VE tables for each injector bank (similar to the dual table code),

4) Stepper motor IAC control: for most common EFI idle control motors, as well as support for MegaSquirt's FIdle valve control.

5) Ignition Control: MegaSquirt-II code has the ability to control a variety of ignition modules (including those that require dwell control). It supports 1 coil/distributor configuration, as well as the Ford EDIS system, and GM DIS system.

Q. How do I install MegaSquirt-II?

A. Full installation instructions are at the MegaSquirt-II installation page.

Q. Does MegaSquirt-II work with the stimulator?

A. Yes, but with the limitation that you won't be able to verify or test the ignition or IAC controller functions, and the VR tach input circuit may not work (depending on tolerances).

Q. How do I upgrade the embedded code for MegaSquirt-II?

A. MegaSquirt-II embedded code can be upgraded with the bootloader using the same procedures as for the 68HC908 processor. The .s19 file is different, however, and care must be taken to load an appropriate file. Full details are here: www.megamanual.com/ms2/code.htm

Q. Does MegaSquirt-II need its own tuning software?

A. No, MegaTune works fine. However, to access the variables, you must configure MegaTune to recognize that you are tuning a MegaSquirt-II. To do this, you need to find the lines in the settings.ini file in your mtCfg folder (usually in C:\Program Files\MegaSquirt\Car1\mtCfg) that look like this:

#  set MS_I       ; Original MegaSquirt
#unset DUAL_TABLE ; MS-I with two pages
#unset MS_II      ; MegaSquirt-II
#unset MSNEDIS    ; MSnEDIS ignition variant
#unset PIC_SQUIRT ; PIC squirt
#unset MSNS_EXTRA ; James Murray's experimental quad table code

and edit it (using notepad.exe) to look like this:

#unset MS_I       ; Original MegaSquirt
#unset DUAL_TABLE ; MS-I with two pages
#  set MS_II      ; MegaSquirt-II
#unset MSNEDIS    ; MSnEDIS ignition variant
#unset PIC_SQUIRT ; PIC squirt
#unset MSNS_EXTRA ; James Murray's experimental quad table code

Note that we have 'unset' MS-I and 'set' MS-II. The mtCfg.exe utility can be used to do this.

Q. Does MegaSquirt-II work with the flyback board?

A. Yes. MegaSquirt-II fully supports the flyback board in a plug and play operation. Note that you may need to set-up your PWM parameters (as well as the rest of the tuning parameters), as you are installing a chip with 'default' values.

Note that in order to physically fit the MegaSquirt-II into the case with the flyback board, you may have to leave the:

• BDM header,
• a jumper header, and
• the bootloader switch

off the board to make room. None of these components are necessary to run the car.

Q. Does MegaSquirt-II work with the MegaView?

A. Partially. MegaView will display the fuel parameters, but not the ignition or IAC parameters. There is an embedded code update for MegaView that will allow these parameters to be displayed.

Q. How do I set up an ignition system with MegaSquirt-II?

A. To provide improved engine performance, better fuel economy, and reduced exhaust emissions, MegaSquirt-II can control spark advance (timing). MegaSquirt-II V1.000 has the ability to control a variety of ignitions which have 1 coil and a mechanical distributor to distribute spark.

To wire your ignition to MegaSquirt-II, you need to deduce the function of at least four wires:

• tach signal,
• advance control signal,
• override (cranking) signal (if used),
• ground.

For example, with a GM HEI 7-pin module, these wires are:

• tach signal is a purple wire with a white trace [pin R],
• advance control signal is a white wire [pin E],
• override (cranking) signal is a tan wire with a black trace [pin B],
• ground is a black wire with a red trace [grounded to distributor case].

GM and most other electronic spark driven reluctor electronics trigger on the negative going zero transition after a positive voltage. While they could trigger on the rise that is not how they were designed. Thus polarity of the reluctor signal is critical to proper function.

See the MegaSquirt-II Ignition page for more details.

Q. What types of idle air controllers (IAC) can I use with MegaSquirt-II?

A. MegaSquirt-II has a few options for controlling idle speed. These fall into the broad categories of stepper motor IAC, and Fast Idle Valves (ON/OFF or PWM'd). Note that the default is a fast idle valve (like MegaSquirt), so you will have to change this setting using the MegaTune^II to use a stepper motor IAC. You will also have to run additional wires from the MegaSquirt^® PCB to your IAC.

See the MegaSquirt-II IAC page for more details.

MegaSquirt-II can control an bipolar stepper motor Idle Air Controller (IAC) to adjust the amount of air entering the intake manifold based on the engine's coolant temperature. The number of IAC "steps" is user set in a 10 element table. With IAC control, MegaSquirt-II can be tuned to adjust the engine speed at crank, starting, warm-up, and running conditions, preventing stalling and lowering emissions. MegaSquirt-II version 1.000 code does not have feedback idle speed control based on actual RPM, however. This will be incorporated into later developments of the code.