7.8 Advanced Engine 7 ADDITIONAL ITEMS: BEYOND BASIC FUEL AND IGNITION CONTROL
7.8.1.3 Speed value from a remote CAN device In the case where you have, say, a CAN-connected transmis-
sion controller that is already calculating vehicle speed, you can simply configure MS3Pro to collect this number.
Analogue sensor should be set to Off and CANVSS specified as the Input. Set scaler% and lag factor. Internally,
MS3Pro stores speed in units of 0.1 ms-1 (meters per second). To convert from a remote device using mph, a
scaler of 46% would apply. Configure the CANVSS offset/table/id through the CAN menus.
7.8.1.4 Pulse data from a remote CAN device This is similar to option 2, but the VSS connects to a remote
CAN device, the time between pulses is collected and MS3 calculates the speed. Analogue sensor should be set
to Off and CANPWMin specified as the Input. Set wheel diameter, VSS position, number of teeth, PWM port and
lag factor. Configure the CANPWM offset/table/id through the CAN menus.
7.8.1.5 Menu settings
• Analogue sensor - If using an analogue sensor (method 1) this is set to the analogue input. Otherwise, set
it to Off
• Full scale speed - only used with an analogue sensor. Sets the speed reported on a 5V input. Assumes 0V
= 0 speed.
• Input - specifies either the digital pulse input or CAN input. Not used with analog sensors.
• Wheel diameter - only applies to methods pulsed input modes.
• VSS position - either wheel or driveline - applies to methods pulsed input. If using driveline, be sure to set
your final drive ratio.
• Speed sensor #teeth - how many teeth the reluctor has - used with pulsed input
• PWM port - the CAN PWM "port" being used - only used with pulsed input over CAN.
• Scaler - applies a scaling to the CAN collected speed value, for units conversion. Applies if using CAN.
• Smoothing lag factor - Smoothing on the speed value. Lower numbers mean more delay and smoothing.
Sensible range is 15-100.
7.8.1.6 VSS dot smoothing These settings control how the VSSdot (acceleration) calculation is performed.
The lower the sample interval, the more responsive the calculation but the noisier it will be. Experimentation will
be required to get the best settings for your application. Calculating launch acceleration is particularly difficult to
get right. Very low tooth counts and wheel speed collected via CAN will be the most difficult due to the low data
rate and the communication delays.
7.8.1.7 VSS sampling The MS3Pro calculates vehicle speed by counting the number of pulses in a sample
interval time, separate from (and shorter than) the VSSdot sample interval. Normally 50ms is OK and gives
excellent smoothing. Hard accelerating vehicles will need to lower this number for improved zero-speed response.
7.8.1.8 VSS output This allows the MS3Pro to provide a scaled output based on speed sensor #1 to control a
speedometer.
• VSS output - specifies which output channel to use.
• VSSout units - valid units are as follows:
– Time
– Pulses per mile
– Pulses per kilometer
• Scale - If “pulses per mile” or “pulses per kilometer” is selected, this is how many pulses to put out per unit of
distance. If “time” is selected, the time between output pulses is calculated as time factor / speed in meters
per second.
AMP EFI MS3Pro manual version 1.202, firmware 1.5.0, 4/21/2017 Page 230
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