bales 1 Posted August 13, 2007 Have been trying to get the tacho to work tonight and am getting a bit frustated to be honest. Has anyone actually done this and got it to work as there seems to be a lot of talk and showing of diagrams but no actual experience of someone who has done it and has it running. I have tried both methods shown on here, the first one I tried was posted by PeterT I think and had the zener diode aswell in it with a 1k resistor. This worked but the rev counter had no correlation to the revs just wobbled about a lot So then I tried the one that Hilgie posted yesterday which strangely didn't have a zener in the circuit and used a 2k2 resistor instead of the 1k. This didn't work at all without the zener - not even a flicker. So we tried the first circuit with the 2k2 resistor and it started to be a bitt more promising as it idled roughly correct but was very laggy - though it did actually increase and decrease the revs, just slowly and behind the engine by a fair amount. It doesn't really fill me with confidence as I am not sure even if it does get less laggy that it is going to be particularly accurate, does anyone have a definitive diagram that they know actually works and have done it themselves. I thought that Hilgie's would work as he has a lot of experience but it didnt seem to work at all. On the plus side though whilst we were trying it and my dad was revving it a bit it was dark and I was stood behind I did for once see a foot long flame out of the exhaust which is nice Though it isn't running right and it was also putting a distressing amount of smoke out of the exhaust from the turbo Any help would be very greatly appreciated. Alex Share this post Link to post Share on other sites
Mikey G 3 Posted August 13, 2007 Ive done it, used the standard diagram with 2 1N4004 diodes, 1 1N4744 zener and a 1k 1w resistor. If youve had it working and its lagging you may be having the same trouble as welshpug but i'm not sure if he's cured it yet. Ours worked perfectly first fit. Share this post Link to post Share on other sites
welshpug 1,657 Posted August 13, 2007 not tried mine recently, I'm not sure if the higher wattage Resistor to earth has anything to do with the reaction speed (its not that slow), not had a chance to try a different Wattage resistor as yet but it certainly works well apart from this Share this post Link to post Share on other sites
bales 1 Posted August 14, 2007 Did both of you have the the resistor in the tacho bypassed? Share this post Link to post Share on other sites
welshpug 1,657 Posted August 14, 2007 nope, done sod all to the tacho. Share this post Link to post Share on other sites
bales 1 Posted August 14, 2007 (edited) hmm interesting.... Edited August 14, 2007 by bales Share this post Link to post Share on other sites
bales 1 Posted August 16, 2007 Just to let people know if they may be about to do this mod DO NOT BYPASS THE RESISTOR ON THE PCB INSIDE THE TACHO, I did this as outlined in one method posted on here. This has broken my tacho as it had knackered the IC on the pcb, it is obviously there as a buffer to the incoming signal and by removing it it has fried the chip. The only people who have this mod working as who have posted on this thread have not touched the indside of the tacho, and there's works fine so this is the only reason I can think of. We have been through every component on the tacho pcb with a multimeter and everything else works fine other than the black IC. So this is as a warning. So if anyone has a tacho I could purchase cheap second hand I would be interested, thanks. Alex Share this post Link to post Share on other sites
whizzer71 0 Posted August 16, 2007 I have used this method on two Gti6 conversions and two Turbo conversions and they all worked perfectly fine,didnt do anything to the tacho either !,Fangio now has my Gti6 and can confirm that works perfectly fine. (Got the info from hilgie). Just keep at it mate,(once you get a new tacho of course) Good luck Tris Share this post Link to post Share on other sites
maxi 36 1 Cars Posted August 19, 2007 You either modify the signal to work with a 205 tacho, or you modify the tacho to work with the signal. Nobody should modify them both. My gti6 I modified the 205 tacho with no problems whatsoever (bypassed the resistor and capacitor), then took the output from the ecu, connected it to it and bobs your inlaw. Cant understand how you blew up your tacho??!?!?!?!?!? Maxi Share this post Link to post Share on other sites
Super Josh 4 Posted August 19, 2007 Just to clarify, you mod the tacho if you are going to use the output from an ECU, either original pug or aftermarket one. Don't modify the tacho if you are using the output from a coil/coilpacks etc. The resistor/capacitor combination protect the tacho IC from the relatively high voltage produced by the coil/coilpacks. Josh Share this post Link to post Share on other sites
petert 586 Posted August 19, 2007 Ive done it, used the standard diagram with 2 1N4004 diodes, 1 1N4744 zener and a 1k 1w resistor. I've done the same with a VDO tacho and it's 100% accurate from 100% accurate from 1000-7500. I can't make any guarantees for Peugeot tachos! Share this post Link to post Share on other sites
