Alfasprinter Posted February 24, 2012 Share Posted February 24, 2012 Hi all ive just wired up a linkplus v14 into my racecar with its new motor, trying to tie up the loose ends/wires. it says it runs a low level tacho of the tacho output, i hav an autometer tacho in it now which i ran with the old engine with a single coil and dizzy, now it has subaru coilpack running wasted spark so i cant just run of coil negative. how do people get around this or where can i buy a low level tacho? Cheers Quote Link to comment Share on other sites More sharing options...
DJZ Posted February 24, 2012 Share Posted February 24, 2012 The Autometer tach should work fine off the computer or the ignitor depending on which one you are using, I had to run the tach in my Z off the Link ignitor originally. Quote Link to comment Share on other sites More sharing options...
keltik Posted February 24, 2012 Share Posted February 24, 2012 The output from the Link is to drive the Tacho. So you dont need to hook the tacho in to anything else. The ECU will give it the rpm signal. The link can only drive a low level tacho tho. 99% of aftermarket tachos are low level and all of the factory tachos ive seen with the exception of diesels are also low level. So it will work fine. Quote Link to comment Share on other sites More sharing options...
kpr Posted February 24, 2012 Share Posted February 24, 2012 most older stuff will be coil negative. wont run off link output. your autometer may run off either / i haven't had anything to do with them. otherwise you can make a small circuit that will combine the signal from your wasted spark coils (long as ignitor isnt built in) to go to your tach. mitsi vr4's have these or you can make your own for 50C or so. easy as. will find the diagram if you need to do this.. Quote Link to comment Share on other sites More sharing options...
keltik Posted February 24, 2012 Share Posted February 24, 2012 I thought the link output grounded the signal to the tach....hence low level drive. Its unable to supply a voltage from that output. So will work with any tacho that runs from a coil negative. Or at least - mine does. Quote Link to comment Share on other sites More sharing options...
kpr Posted February 24, 2012 Share Posted February 24, 2012 low level they mean just gives a negative pulse, running from coil neg is far more agressive. sometimes you may get away with it, sometimes you can change a resistor in the tach circuit to a lesser value to make the low level input work. some people even use a relay coil on low level signal, to up the signal for coil neg tach. ^ probably not the right tech explanation. but pretty much how it goes Quote Link to comment Share on other sites More sharing options...
thegreatestben Posted February 24, 2012 Share Posted February 24, 2012 Rich, this is what I had to make for my MR2 when converting to wasted spark. Worked like a treat Quote Link to comment Share on other sites More sharing options...
keltik Posted February 24, 2012 Share Posted February 24, 2012 low level they mean just gives a negative pulse, running from coil neg is far more agressive. In the G3 and G4 firmware you can change the duty cycle of the tacho drive. Not sure about the linkplus. Quote Link to comment Share on other sites More sharing options...
mjrstar Posted February 25, 2012 Share Posted February 25, 2012 I have a link plus and autometer tacho in my starlet... i have tried it with it wired from the igniter output and from the ecu output, and although it does work it seems slow/lazy either way.. Pretty much gave up on paying attention to RPM's, just change up when it's feels about right.. Quote Link to comment Share on other sites More sharing options...
kpr Posted February 25, 2012 Share Posted February 25, 2012 Rich, this is what I had to make for my MR2 when converting to wasted spark. Worked like a treat this is drawing i was talking about ^ +1 for change gear when it stops revving Quote Link to comment Share on other sites More sharing options...
madmitsi Posted February 25, 2012 Share Posted February 25, 2012 wonder if i make one of those^^^ up it will fix this Quote Link to comment Share on other sites More sharing options...
kpr Posted February 25, 2012 Share Posted February 25, 2012 maybe, more details on setup Quote Link to comment Share on other sites More sharing options...
madmitsi Posted February 25, 2012 Share Posted February 25, 2012 got a 4g63t in my 1978 galant and the vid with the tacho bouncing is from the -ve of coil 1 its the only signal i can get to move the tach originaly they run from coil -ve but with the new setup it bounces, had it wired into the ignitor for tach signal but i think the signal is to low to run the old school tach been tryin to suss it for ages Quote Link to comment Share on other sites More sharing options...
thegreatestben Posted February 25, 2012 Share Posted February 25, 2012 you should make one and try it, it's like $4 worth of bits or something rediculous Quote Link to comment Share on other sites More sharing options...
madmitsi Posted February 25, 2012 Share Posted February 25, 2012 yea mite be the go, a guy on msport said to try a signal amplifier http://www.anythingelectronic.co.nz/pdf/ta12.pdf he recons make him an offer cost 160 retail thought theres gotta be another way Quote Link to comment Share on other sites More sharing options...
Ned Posted February 25, 2012 Share Posted February 25, 2012 Low level means it gives a PWM output of 0-5V. It could be an open collector output which means you can get any signal as it only shorts to ground so you could have a pullup resistor to any voltage to create a PWM signal from 0-5V or 0-12V or any other rail you have available. Old tachos that go to the negative of the coil do not actually work by shorting the input to ground, they work on a 30-40V pulse that occurs when the negative of the coil is released and a high voltage is created for spark by the coil. To get old tachos to work with your link output, you need a resistor, (a diode and a zener diode isn't a bad idea), an inductor and a transistor. Feed the output from the link to the anode of a diode (like a 1N4007) and the cathodes of the 1n4007 and a 5V1 zener diode together. The zener diode Anode goes to ground. Now put a 1K resistor from the two diodes to the base of an NPN transistor (like a BC337 or a PN2222 etc) and the emitter to ground. The collector fo the transistor goes to one side of the coil/inductor (just use a cheap 12V relay coil for this) and the other side of the coil goes to 12V. The bit you now feed into the tacho comes from where the transistor and the coil connect. I should have just drawn a fricken picture, would have been quicker :/ Quote Link to comment Share on other sites More sharing options...
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