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Hardware requirements

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Speeduino uses the Arduino Mega 2560 R3 as the controller. All official and most clone boards appear to work fine. Note that there are minor differences with the Mega R2 board that can cause some small issues, however as it is nearly impossible to find an R2 board currently (R3 has been the available version for a long time) this should not be an issue for most people.

Update: While the connection issues with some clone boards appear to have been resolved, an alternative solution is to use Bluetooth for wireless tuning of any Mega version, as the Bluetooth option bypasses the on-board UART (serial) chip.


Crank sensor

This is arguably the most important sensor for Speeduino to function correctly. The signal going to the arduino needs to be a 0v-5v square wave series of pulses representing teeth on a wheel running at crank (or cam) speed. This wheel must have a 'missing' tooth in order to provide position information as well as the engine RPM. Tested wheels currently are 4-1, 12-1, 36-1 and 60-2 wheels.

A VR sensor can be used, however as the board does not contain any sort of conditioner, an external module will be needed. The JBPerf dual VR conditioner (http://forum.jbperf.com/viewtopic.php?f=6&t=1089) has been tested to work, however any similar module that outputs a 0v-5v square wave should work fine.


TPS sensor must be of the 3 wire potentiometer type, rather than the 2 wire on/off switches found on some throttles. If your TPS is a 3 wire sensor then it will almost certainly work, but remember to calibrate it within Tuner Studio when you first plug it in.

MAP (Manifold Pressure)

Recommended MAP sensor is the MPX4250 from Freescale, however many MAP sensors are supported. If you want to use one that is not included in the list (Under Tools->Map Calibration in TunerStudio) then please make a new thread in the forum requesting this. Other sensors can and will work just fine, but you will need to calibrate these within TunerStudio against a different set of values.

Temperature Sensors (CLT and IAT)

Any standard 2-wire thermistor sensor can be used for these temperature functions. Calibration of these sensors can be performed through the Tools menu in TunerStudio. The default bias resistor value is 2940 Ohms.



Speeduino injector drivers use on/off (not PWM) control and are designed to work with "High-Z" injectors. This type of injectors are also known as "saturated" or "high-impedance" that use full battery voltage to control the injector open cycle, and generally the impedance is greater than about 8 Ohms. If you are running "Low-Z" ("peak and hold" or PWM-controlled) injectors that are lower impedance, you will need to install series resistors on these to avoid damaging the board with excessive current. The resistor ohms and watt rating can be calculated by Ohm's Law, or use an Internet calculator page such as the Speeduino Injector Resistor Calculator.


Current versions of the Speeduino use low-power output signals, designed to work with external small-signal ignition coil drivers, whether a separate type (module or ICM, igniter, IGBT, etc.), or built into the coil assembly ('smart' coils). This method permits Speeduino to have great flexibility to control most types of ignition systems. Attaching the Speeduino outputs directly to a traditional high current ("dumb" or 2-pin) ignition coil without an ignition coil driver WILL cause damage to your Arduino.

How Speeduino controls ignition circuit power In prior history, the coil driver was a set of mechanical contact points ("points"), simply replaced today by an electronic version. The added coil driver can be anywhere from inside the Speeduino to inside the coil assembly; though near or in the coil reduces electrical noise:

The wasted-spark version is below to show how it is identical in operation, but with the high-voltage spark returning through the second spark plug to complete the circuit:

A good run down of 'smart' coil types can be found at: http://www.megamanual.com/seq/coils.htm. There are many ignition modules available that Speeduino can use to control standard coils, or for smart coils you can generally use 4 or 5-pin types as these will always be logic level, although some 3-pin coils are also of this variety. GM LS1/2 coils are an example of powerful smart coils that are commonly used and can usually be obtained easily and cheaply.

(Note: In the past, some ignition control modules with current limiting or dwell control features (e.g., 1970s GM HEI, Bosch '024' types, and Ford DS1) were referred-to as "smart" modules. While still true, common terminology of individual ignition coils with at least a driver integrated, or newer technology with greater controls (e.g., controlled spark duration or multi-spark) are all considered "smart" coils. You must know the control requirements of the specific drivers, control modules, or coils you intend to use in order to operate them properly with Speeduino.)

Aux Outputs

Low Current

Some Speeduino versions include an 8-channel ULN2803A Darlington transistor array IC that is capable of switching up to 1/2 amp per channel. These auxiliary outputs are sufficient to switch small devices directly, or to switch power-handling devices, such as power MOSFETs and solid-state or electro-mechanical automotive relays. Configuration and settings of these outputs is described in the Configuration / Tuning section.

Medium Current

v0.3x and later boards include medium-power MOSFET auxiliary outputs to switch up to 3 amps directly. These outputs are commonly used to operate idle valves, boost-control valves, VVT solenoids, etc., or to control relays for handling much larger loads, such as electric radiator fans. Configuration and settings of these outputs is described in the Configuration / Tuning section.