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| HOW??: After market TACHO with S13 SR20det ECU http://ozdat.com.au/forum/viewtopic.php?t=33839 |
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| Author: | stevoooish [ Wed Jul 01, 2015 6:34 pm ] |
| Post subject: | HOW??: After market TACHO with S13 SR20det ECU |
Hello everyone, yes the tacho is supposed to be suited to 5v ECU output. i have been trying to get a new tacho working with the SR ECU. i have joined the TACHO out put from the ECU to the green on the Tacho and nothing. can i seek signal from Positive on the coilpack or any other source. my auto electrician sad that the signal required a pull down resistor. i will try but have little faith with this suggestion. this is supposed to be simple my god. anyone else feeling my pain or have solutions. Cheers, |
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| Author: | danielmcdonald [ Wed Jul 01, 2015 7:48 pm ] |
| Post subject: | Re: HOW??: After market TACHO with S13 SR20det ECU |
Hey mate Wire in a resistor between ign 12v wire and signal wire from Ecu. |
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| Author: | Baz [ Thu Jul 02, 2015 10:45 am ] |
| Post subject: | Re: HOW??: After market TACHO with S13 SR20det ECU |
1.2k to 1.5K 1/4 watt will do the job. Works for us. BTW, usually called a pull up. |
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| Author: | stevoooish [ Thu Jul 02, 2015 11:19 am ] | |
| Post subject: | Re: HOW??: After market TACHO with S13 SR20det ECU | |
Attachment: Diagram.jpg [ 18.87 KiB | Viewed 3494 times ]
1.2k to 1.5K 1/4 watt will do the job.
sorry guru,Works for us. BTW, usually called a pull up. Is this what you mean? i dont see why i need to pull up as the tacho is supposed to be 5v and i thought the ECU output 5v also. |
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| Author: | stevoooish [ Thu Jul 02, 2015 11:20 am ] | |
| Post subject: | Re: HOW??: After market TACHO with S13 SR20det ECU | |
Hey mate
hello Dan,Wire in a resistor between ign 12v wire and signal wire from Ecu. thank you. do you mean as per my reply to GURU? |
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| Author: | xfacta [ Thu Jul 02, 2015 7:53 pm ] |
| Post subject: | Re: HOW??: After market TACHO with S13 SR20det ECU |
Go with the pull-up resistor. A range of values will work, it's not to critical. 1.2k ohms to 4.7k ohms. The reason is your tacho is expecting to see a signal pulsing from 0volts to 5 or 12volts, the tacho has strictly an input only. The ECU tacho output is "open collector" - it switches a voltage to ground (0 volts) and doesn't "output" a voltage. So all your tacho sees is 0volts the whole time. The pull up resistor puts a voltage on the tacho signal wire for the ECU to pull down to 0 volts periodically. Too small a value resistor and the transistor in the ECU will be trying to switch amps instead of milliamps and will blow. |
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| Author: | stevoooish [ Fri Jul 03, 2015 11:21 am ] | ||
| Post subject: | Re: HOW??: After market TACHO with S13 SR20det ECU | ||
Ok randomly this worked. i found this by fluke
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