Hey guys, I've currently got a s16 engine in my 205 and I cannot get the Speedo or rev counter working, I am looking at fitting digital gauges shortly but was wondering where the rev counter cables actually connect on the engine as I've been unable to follow the cables back, thanks
Speedo you can just use the standard 205 cable drive speedo, so there's no reason this shouldn't work just as it would have done with the original 8v engine - chances are either the cable has broken or it's come unclipped at one end. You'll ideally need to use the dual mechanical/electrical output speedo drive that's found on various 306 Phase 1 models like XSi's and S16's so that the ECU sees a speed signal.
For the rev counter you'll either need to use a tacho adapter of some form, or remove the rev counter and make a modification to the PCB to bypass the filtering circuit. The reason that it's not working is that the 205 rev counter expects to see the pulse back from the ignition coil, whereas the S16 ECU sends out a nice square wave 12v signal.