Spark Manual

The controller box is the MegaSquirt EFI hardware. The MegaSpark was initially designed and tested on version 2.2, but it may also be compatible with other versions. The software aims to provide a fully functional advance controller without requiring modifications to the MegaSquirt hardware, aside from standard experimentation with the MegaSquirt tach input. Some options may necessitate modifications or the addition of a daughterboard. For inquiries regarding the purchase and construction of MegaSquirt hardware, please refer to the provided link. The MegaSpark is designed to operate with a single input trigger per spark. This requirement can be met in various ways, with the input source potentially coming from the distributor (which must be locked), crank, cam, or flywheel. Similar to MegaSquirt, experimentation may be necessary depending on the sensor used. A clean input signal is essential for the proper functioning of MegaSpark. The input trigger must occur at least 5 crank degrees before the total desired advance (for 8K RPM, this should be increased to 8 crank degrees before for 12K RPM). It must also occur after the previous spark, imposing a maximum limit on the degrees BTDC of the input trigger. For odd-fire engines, the "Static Timing" must be less than the shorter spark interval. For example, in a V-6 engine with 90-degree and 150-degree spark intervals, the input trigger must be closer than 90 crank degrees BTDC. Additionally, each trigger must occur at the same degrees BTDC for each spark, meaning the spacing of the triggers must match the odd interval spacing of the sparks. Engines with an odd number of sparks per crank revolution, such as a 4-stroke 6-cylinder engine (which produces 3 sparks per revolution), cannot trigger from the crank. When mounting a sensor, it is recommended to position it for an input trigger approximately 45 crank degrees BTDC, allowing for up to 40 degrees of total timing advance. The input trigger position can be adjusted in the PC software under the label "static timing," so an adjustable sensor mount is not strictly necessary. However, for a Hall effect sensor, the ability to adjust the sensor/magnet air gap is advisable, which can be accomplished using washers to shim the mount. The exact position of the sensor relative to the TDC mark is not critical; what matters is the sensor's position concerning its triggers. It is important to ensure that there will be no issues with mounting triggers, such as interference from balance holes in the back of a crank pulley, before finalizing the sensor installation. The sensor/triggers can be positioned for a static timing greater than 45 BTDC, provided the specified limits are not exceeded. A static timing of 56.5 degrees has been successfully tested, but smaller values are recommended for optimal timing accuracy at lower RPMs. The spacing between triggers should be as precise as possible. When sensing triggers on the distributor or cam, it is important to remember that distributor/cam degrees are half of crank degrees. Therefore, with the crank at TDC, a distributor/cam trigger 22.5 degrees from the sensor is equivalent to 45 crank degrees. The outer ring of harmonic balancers is subject to vibration, which may not be the most suitable location for mounting triggers. Specifics on connecting particular OEM sensors are not provided, and while some possible interfaces are mentioned, any issues will need to be addressed by the user. Circuit #1 has been verified with a latching Hall effect sensor, but other circuits remain untested, and their functionality cannot be guaranteed. It is also important to note that the logic sense is critical; the microcontroller detects the input trigger when U4 is activated. The sensor requires +5V, and Hall effect sensors may have an internal regulator, accepting power from 5V to 30V, but the noisy nature of the environment should be considered.

The MegaSquirt EFI hardware serves as a versatile engine management solution, allowing for precise control over ignition timing and fuel delivery in various engine configurations. The MegaSpark system is specifically tailored to enhance ignition timing through a single input trigger, ensuring that the timing is accurate for optimal engine performance. The requirement for a clean input signal cannot be overstated, as any noise or interference can severely impact the system's ability to function correctly.

When implementing the MegaSpark, it is crucial to consider the timing of the input trigger relative to the engine's crankshaft position. The specified timing parameters, such as the need for the trigger to occur before the desired advance, are essential to prevent misfires and ensure smooth engine operation. The system's adaptability to different input sources, including locked distributors, crank sensors, and cam sensors, highlights its flexibility in accommodating various engine designs.

The installation of the sensor should be approached with care, ensuring that the position allows for the necessary timing adjustments while avoiding potential mounting conflicts. The recommendation to set the sensor approximately 45 degrees BTDC is based on providing sufficient timing advance while allowing for adjustments through the software interface. This feature simplifies the installation process, as precise physical alignment is not mandatory.

In terms of wiring and interfacing, users should be aware of the electrical characteristics of the sensors used, particularly the Hall effect sensors, which may operate over a range of supply voltages. The importance of logic sensing in the circuit design is critical, as it directly affects how the microcontroller interprets the input trigger. Therefore, careful attention must be paid to the circuit design and component selection to ensure reliable operation.

Overall, the MegaSquirt EFI hardware and MegaSpark ignition controller represent a sophisticated solution for engine management, providing users with the tools necessary to optimize engine performance through precise timing control and adaptability to various engine configurations.The controller box is the MegaSquirt EFI Hardware. The MegaSpark was originally designed & tested on v2. 2, but may work on other versions. The software was designed to yield a fully functioning advance controller with no modifications to the MegaSquirt Hardware (beyond the normal MegaSquirt tach input experimenting). Some options may require modi fications or an additional daughter board. Please refer to the above link and for questions on purchasing and building the MegaSquirt hardware. The MegaSpark is designed to operate with *one and only one* input trigger per spark. This requirement can be satisfied in a variety of different ways. The input source can come from the distributor (required to be locked), crank, cam, flywheel. As with MegaSquirt, some experimenting maybe required depending on the sensor. A clean input signal is an absolute must with MegaSpark! The input trigger must occur at least 5 crank degrees before the total desired advance (for 8K RPM, increase to 8 crank degrees before for 12K RPM). Also, it must occur after the prior spark - this places a maximum on the degrees BTDC of the input trigger: For Odd-Fire: The "Static Timing" must be less than the shorter spark interval.

For example, on a V-6 with 90 degree & 150 degree spark intervals, the input trigger must be closer than 90 crank degrees BTDC. Also, each trigger must occur at the same degrees BTDC for each spark, so the spacing of the triggers must match the odd interval spacing of the sparks.

This means that engines that have an odd number of sparks per crank revolution, such as a 4-stroke 6 cylinder (3 sparks per rev), can not trigger off the crank. When mounting a sensor, it is suggested to position it for an input trigger ~45 crank degrees BTDC. This will allow up to 40 degrees total timing advance. Note: the input trigger position is settable in the PC software (under the label of "static timing"), so it is not necessary to have an adjustable sensor mount (though for a hall effect, you should have the ability adjust the sensor/magnet air gap - I just use washers to shim the mount).

Nor do you have to try to achieve an exact 45 degree position. Also note the position of the sensor relative to the TDC mark is not important - it is the position of the sensor relative to its` triggers. In the diagram, I purposely put a funny angle between the TDC mark and Hall Effect sensor to empathize this point.

So you are free to position the sensor where ever it is easiest to mount. However, you should verify that there will not be any problems in mounting triggers, such as might be caused by balance holes in the back of a crank pulley, before actually mounting the sensor. You can position the sensor/triggers for a greater than 45 BTDC static timing as long as the limits above are not exceeded.

I am running 56. 5 degrees, but smaller values of static timing are suggested for best timing accuracy at lower (idle) RPM`s. The spacing between the triggers needs to as accurate as possible. When sensing triggers on the distributor or cam, remember that the distributor/cam degrees are 1/2 of the crank.

So with the crank @ TDC, a distributor/cam trigger 22. 5 degrees from the sensor to be equal to 45 crank degrees. The outside ring of Harmonic Balances are subject to vibration (kind of what they`re designed to do), so may not be the best location for mounting triggers. Given that I have no knowledge of OEM sensors, I can not give you any specifics on connecting particular sensors.

Below are some possible interfaces, but you will have to resolve any problems. I have checked Circuit #1 with a latching hall effect, but otherwise the circuits are untested. I can not promise that they will work. Please note that the logic sense is important. The uP sees the input trigger when U4 is turned ON. * +5V for Sensor - Hall Effects may have an internal regulator and accept power from 5-30V. But considering the noisy natur 🔗 External reference