Thought i'd make a quick post on this as DaveG had asked me previously about the possibility of making a box to change rpm signals for engine swaps. ie driving a 4 cylinder tach from a v8 etc. Had to knock something up quickly for myself yesterday for the E31 as i foolishly thought the tach was 2 ppr. Can be setup anyway you like via software. I'll also be making a CAN version to drive the E46 instrument cluster for the drift build. So if you need one let me know or i'm happy to post the code and schematic for diy builds.