Edit Mar 3 2022: Users have been reporting issues with the BETA firmware, the BETA firmware has been taken down, working on fixing the issues.
Get the firmware here, Software and Documentation | 14Point7
-For MegaSquirt 3 ECU, when “SLOWHEAT2” serial command is sent, Spartan 3 will delay the LSU heater startup for up to 10 minutes until it detects that RPM is greater than 300 over CAN Bus. After 10 minutes the LSU heater will heatup even if no RPM is detected. Simplified Dash Broadcasting must be enabled on the MS3 ECU; Tuner Studio → CAN-Bus/Testmodes → Dash Broadcasting → Set Enable to “On”.
-Delay CAN Bus initialization for 10 seconds.