If your RPM shows "dips" (sometimes jumping, usually to 0), use the latest firmware, at least [ 2009-10-12]

To understand more of the analog and rpm input, a schematic would really help.

RPM and wheelspeed input

Beware that using the RPM input might require input voltage threshold adjustment with a simple pullup / pulldown resistor in some cases, depending on input voltage level. It is easy, but not plugandplay in all cases.

RPM input HW

rpm_input measures 5V if left open

rpm_gndref to adjust voltage threshold with pullup/pulldown resistor

RPM input config

Known as "RPM settings" in megatune.

The precision is 1 RPM. Note that display from 230 .. 15999 is possible. Above 9999 the first digit is hexa, so

For wheelspeed input

To support 1 pulse per cam-rotation: experimental [doubleRPM-firmware]

RPM tricks

The sensing voltage-level-threshold is adjusted with RPM-gndref pulldown/pullup resistor (yes, soldered; not configurable in software) value. Depending on the input signal specs, you might not need to connect RPM-gndref at all (eg. for 5..10V amplitude AC signal). The round device will not be harmed if you first try with RPM-gndref not connected.

First measure DC voltage on the output RPM signal (that you want to measure) when connected to nothing, but engine running.

Measure DC voltage

Mega Tune Setup

RPM gauge range (max RPM) can be increased in round.ini file, change the line:

 tachometer        = rpm,           "Engine Speed",       "RPM",     0,  8000,    300,   600, 3000, 5000, 0, 0


 tachometer        = rpm,           "Engine Speed",       "RPM",     0,  11000,    300,   600, 3000, 7000, 0, 0

or whatever max RPM you find appropriate if 11000 is not enough. The last values are responsible for the color-"alarms".