Ted 0 Posted April 7, 2006 can anyone tell me what type of signal is generated form a wasted spark system (i,e modern pugs), is it sinusoidal from each coil ? what type of signal do the standard 205 dials look for ? thanks Share this post Link to post Share on other sites
M3Evo 0 Posted April 7, 2006 Think the 205 dials look for some funny 350v signal whereas more modern things seem to put out a square wave 5v thing (might be totally wrong about the modern bit though) Share this post Link to post Share on other sites
petert 607 Posted April 7, 2006 what type of signal do the standard 205 dials look for ?thanks The back emf from the coil, typically 350-400V. Share this post Link to post Share on other sites
Mad Professor 7 Posted April 8, 2006 If i renamer right from the msefi site that the ford edis coil pack's CTO (Clean Tacho Output) is a +5v or +12 Sqare wave. Share this post Link to post Share on other sites
jochem 0 Posted April 8, 2006 I connected my gti6 tacho wire from the ECU to an osciloscope. I made a drawing of the signal that i can scan in if that is of any interest? It was indeed square and 6volt. Share this post Link to post Share on other sites
petert 607 Posted April 8, 2006 I'm not sure if you're missing the point, but I'll elaborate anyway. When an ignition coil is grounded, by points or ignition module, then released, a high voltage will be induced on the primary side of the coil of approx 400V and a very high voltage (20kV) on the secondary side. If you connect a CRO to the primary side, set read a high voltage, you will see two wave forms - a 12V square wave and a 400V wave, called a back emf (electro motive force). Some tachos are designed to read the 12V square wave (eg 405) others the 400V wave (eg 205). Share this post Link to post Share on other sites
