4.5 Fuel injectors 4 WIRING
Some bikes are fitted with a Gear Position Sensor. This 0-5V analogue input can be used directly to determine
gear, and can connect to any unused analog input. The MS3Pro can also determine the gear you are in by
comparing the engine RPM and wheel speed.
When used with a MegaShift transmission controller, the MS3Pro can read speed and gear information through
the MegaShift over CAN. No additional sensor wiring is needed, other than the wires for the MegaShift.
4.4.8 Generic on/off switches
There are several inputs the MS3Pro can use as switch inputs for triggering launch control, nitrous, table switching,
or other functions. Valid inputs include the Digital Switched In inputs, the Digital Frequency In inputs, and Digital
Switched 12V In. Digital Switched 12V In activates when connected by a switch to a 12 volt source. All other on/off
switch inputs activate when connected through a switch to ground instead. The Digital Switched 12V In function is
set up this way to allow using it to detect when a nitrous system is energized and arm the system, but can be used
for other functions as well. The illustration below shows typical switched input wiring.
Caution: Do not wire the Digital Switched 12V In wire directly to any input that is supplying power to a trans
brake or other high powered solenoid. This may result in damage to the input circuit. Instead, use the 12 volt
power to the solenoid to switch a relay to control an on/off input.
4.4.9 Other sensors
You can connect any 0 to 5 volt analog signal to the Analog In inputs. The MS3Pro software can use these for data
logging or other functions.
4.5 Fuel injectors
Fuel injectors are pretty simple; one side gets switched, fused 12 volt power. The other side connects to the
MS3Pro injector output. They are not polarized so it doesn’t matter which is which. Current MS3Pro settings have
the firing order hard-coded in, so they always fire in alphabetical order.
If running sequential output on a 12 cylinder engine, High Current 1 and 2 fire the 11th and 12th injectors in the
firing order, respectively.
4.6 Ignition outputs
Ignition coils, as you probably know, require amps or tens of amps of current in order to work. The signal from
the MS3Pro is a much lower-power "logic-level" signal - the kind of signal seen inside computers. So some sort of
device is needed to allow the weak logic-level signal from the MS3Pro to drive the coils.
In other automotive scenarios, this might be done with a relay, which is commonly used to switch a high-power
signal from a source signal of lower power. But a relay isn’t suitable for driving a coil for a number of reasons,
so instead, there’s an electronic device called an ignition module, "ignitor," or "coil driver" to do the job. A few
AMP EFI MS3Pro manual version 1.202, firmware 1.5.0, 4/21/2017 Page 42
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