MR2 rpm signal direct from standalone

Hello

I am trying to get the rpm single working direct from a link on my mr2 rather than taking the signal from the IG amp because i am going coil on plug and planning on nremoving the amp. The signal from the amp spikes below 0v and that seams to be what the rpm counter measures below i have attached a screen shot yellow is the amp output and green is the link out put that does not fire the tacho. I can get it working if i leave the factory IG amp and coil in place and feed the tacho output into the IG amp which obviously is not practical

You need to remove a resistor from the tacho module in order to drive it with the Link. There's a thread on the Link forum that covers the modification required which in this case was on an ST205 Celica but should also cover the MR2: http://forums.linkecu.com/topic/7238-st205-with-cop-conversion-rev-counter/