MartinM 0 Posted June 16, 2006 I have an installed Megajolt Lite Junior system on my 1987 GTi 1.6 8v, which is a complete "add-on" system and I left all the OEM stuff else in place right down to the plug leads cable tied to the strut brace - so it will be easy to revert back if the Megajolt fails - which it shows no sign of doing BTW! It works fantastic! When I finished the install I took the connections off the primary side of the coil, one by one, when the engine was running, to see what would happen. The engine stopped whichever one (of the three) I removed. So does this mean I have: - the Megajolt components supplying the sparks (it has independent power connections to the standard ignition system, so the engine wasn't stopping due to lack of power to the Megajolt) - the ECU picking up something from the standard ignition system to fire the injectors ...and I'll never be able to get rid of the standard ignition components? I believe the rev counter (which works fine) is also being run off the standard ignition system, since I didn't wire up the Megajolt rev counter connections. Is that correct also? Now I've just got a 205Rallye, I've got a Megajolt system lined up for that also. I guess as that is not fuel injected, I will be able to get rid of all the standard ignition components? TIA, Martin Share this post Link to post Share on other sites
jackherer 543 Posted June 16, 2006 - the ECU picking up something from the standard ignition system to fire the injectors the wire coming from the distributor sends a signal to the ECU... ...and I'll never be able to get rid of the standard ignition components? that should be possible, just need to send a signal to the ECU. I believe the rev counter (which works fine) is also being run off the standard ignition system, since I didn't wire up the Megajolt rev counter connections. Is that correct also? yes the tacho will be being driven by the standard ignition stuff, and driving that with the MJ may be trickier. Now I've just got a 205Rallye, I've got a Megajolt system lined up for that also. I guess as that is not fuel injected, I will be able to get rid of all the standard ignition components? yes although the same tacho issues may also apply (do rallyes even have tachos?) Share this post Link to post Share on other sites
MartinM 0 Posted June 16, 2006 the wire coming from the distributor sends a signal to the ECU... that should be possible, just need to send a signal to the ECU. yes the tacho will be being driven by the standard ignition stuff, and driving that with the MJ may be trickier. yes although the same tacho issues may also apply (do rallyes even have tachos?) Thanks Any idea what signal and what timing - and how I can get the equivalent signal from the wasted spark coil pack? I'm sure I could drive the tacho with the MJ - I just never bothered! Yes, Rallyes do have tachos! Share this post Link to post Share on other sites
jackherer 543 Posted June 16, 2006 Any idea what signal and what timing - and how I can get the equivalent signal from the wasted spark coil pack? sorry I don't know, but I would guess its one pulse per cam revolution but no idea of the timing... I'm sure I could drive the tacho with the MJ - I just never bothered! trust me its not as simple as you would have thought... this recent thread by PeterT will give you some idea... Share this post Link to post Share on other sites
MartinM 0 Posted June 16, 2006 I'll get my oscilloscope on the tacho input and see what's going on then....! Share this post Link to post Share on other sites
jackherer 543 Posted June 16, 2006 ah well if you have a scope you'll be able to work out the signal from the distributor to the ECU... as for the tacho, I seem to recall its a high voltage EMF that triggers it.... might be worth a search. Share this post Link to post Share on other sites
M3Evo 0 Posted June 18, 2006 I didn't think the ECU had anything to do with the ignition on GTi cars? Share this post Link to post Share on other sites
MartinM 0 Posted June 18, 2006 I didn't think the ECU had anything to do with the ignition on GTi cars? It doesn't - but it seems to take signals from the ignition to do its thing I think is is true, due to: - my experiments - the lack of any other sensors on the GTi engine to feed into the ECU Share this post Link to post Share on other sites
pugrallye 0 Posted June 18, 2006 to trigger revcounter using later/aftermarket management, you either have to adopt the raping a tacho from a newer pug/citroen or the old diode trick, both of which have been covered on here in past i believe Share this post Link to post Share on other sites
