You can look at this link how the summer works
http://www.aquamist.co.uk/vbulletin/...ead.php?t=1979
The v3 summer needs primary and secondary signal. Trigger point is bsed on the the sum of the IDC signal. The summer can also be triuggered by 0-5V or a voltage-based MAP sensor signal.
The summer is designed IDC to "sum" two idc signals, boost cannot influence the summed output. The RX7 summer is an "add-on" to solve the unusual stepped sequence of the primary and secondary injectors.
We believe the idc signal contains all the information of multiple sensors on the engine. tracking this signal is a good representation of all loads.
As I have mentioned before. It you only need to inejctor water above 25% IDC, you don't need it, just read the idc signal from the secondary injector.