Yaqub Baiani Posted January 23, 2021 Report Share Posted January 23, 2021 I wanted to ask you a question, we are trying to wire up the tach output and get it working with the factor cluster (just a side note, I replaced it with the OEM digital gauge cluster). The ECU I have is the Link G4X AtomX and I got a custom harness from MRP to work for my AE86 with the 16v 4AG motor. that tach output from the ECU is not working with the factory gauge cluster and I didn’t know if you could help guide us to the right path on wrapping this up. It’s the last thing before we can dyno the car. Let me know if you can help. Quote Link to comment Share on other sites More sharing options...
essb00 Posted January 23, 2021 Report Share Posted January 23, 2021 You've got similar issues with @Sushpants He's got it solved. Check out his thread (watch the video link he posted). Quote Link to comment Share on other sites More sharing options...
Adamw Posted January 23, 2021 Report Share Posted January 23, 2021 Your tacho is designed to be driven by a high voltage signal from an ignition coil, not from an ECU. If you have changed to coil on plug then you will have to modify the tacho (not sure if the above post applies to your digital tacho), or you can use a tacho booster like this: https://www.ebay.com/itm/142171581596 Quote Link to comment Share on other sites More sharing options...
koracing Posted January 27, 2021 Report Share Posted January 27, 2021 MSD 8920 tach adapter typically works to convert a low volt ecu output to drive the factory toyota tachs that require the 28v (voltage triggered) input from factory igniter. I've used it on several SW20 single coil/igniter distributor cars with swaps to Gen4 3sgte with coil on plug. Power, ground, input signal from ecu, and output to dash signals. Pretty simple. There are also modifications to the resistor values on the factory tachs if you want to google it that can sometimes be made to allow them to read in the ecu level low voltage directly. I imagine even though the AE86 is older, it still operates under this same prinicple. Quote Link to comment Share on other sites More sharing options...
Yaqub Baiani Posted January 28, 2021 Author Report Share Posted January 28, 2021 23 minutes ago, koracing said: MSD 8920 tach adapter typically works to convert a low volt ecu output to drive the factory toyota tachs that require the 28v (voltage triggered) input from factory igniter. I've used it on several SW20 single coil/igniter distributor cars with swaps to Gen4 3sgte with coil on plug. Power, ground, input signal from ecu, and output to dash signals. Pretty simple. There are also modifications to the resistor values on the factory tachs if you want to google it that can sometimes be made to allow them to read in the ecu level low voltage directly. I imagine even though the AE86 is older, it still operates under this same prinicple. So I bought the following things: 1) https://www.ebay.com/itm/DUAL-STEP-UP-STEP-DOWN-SINE-TO-SQUARE-DIGITAL-SIGNAL-CONVERTER-0-8V-Trigger-/143103138738?_trksid=p2349624.m46890.l49292 2) https://www.ebay.com/itm/DUAL-STEP-UP-STEP-DOWN-SINE-TO-SQUARE-DIGITAL-SIGNAL-CONVERTER-0-8V-Trigger-/143103138738?_trksid=p2349624.m46890.l49292 3) https://www.diyautotune.com/product/axm-100-high-voltage-tach-adapter/ will this work for me @koracing Quote Link to comment Share on other sites More sharing options...
Adamw Posted January 28, 2021 Report Share Posted January 28, 2021 The DIYautotune tach adapter should be similar to the one I suggested or the 8920 that KO suggested, however I have no personal experience with it to say with confidence. The one I suggested is less than 1/2 the price and has worked on everything I have tried it on. The 8920 is also good, but quite expensive here. I have no idea what you were planning on doing with the Sine to square wave conditioners but they are not needed. Quote Link to comment Share on other sites More sharing options...
koracing Posted January 28, 2021 Report Share Posted January 28, 2021 2 hours ago, Yaqub Baiani said: So I bought the following things: 1) https://www.ebay.com/itm/DUAL-STEP-UP-STEP-DOWN-SINE-TO-SQUARE-DIGITAL-SIGNAL-CONVERTER-0-8V-Trigger-/143103138738?_trksid=p2349624.m46890.l49292 2) https://www.ebay.com/itm/DUAL-STEP-UP-STEP-DOWN-SINE-TO-SQUARE-DIGITAL-SIGNAL-CONVERTER-0-8V-Trigger-/143103138738?_trksid=p2349624.m46890.l49292 3) https://www.diyautotune.com/product/axm-100-high-voltage-tach-adapter/ will this work for me @koracing The DIY Autotune device is probably all you need and similar price and function to the MSD 8920. On 1/23/2021 at 12:18 PM, Adamw said: Your tacho is designed to be driven by a high voltage signal from an ignition coil, not from an ECU. If you have changed to coil on plug then you will have to modify the tacho (not sure if the above post applies to your digital tacho), or you can use a tacho booster like this: https://www.ebay.com/itm/142171581596 This looks good. I typically sell the 8920 for $66 so it is a bit more money but it's a known quantity to me thus far. I'll give this a try when the opportunity arises as that is a very good price. Quote Link to comment Share on other sites More sharing options...
essb00 Posted January 28, 2021 Report Share Posted January 28, 2021 If you would watch sushpants' video about his tach fix, the problem with some tach adapters is that they seem to lose enough duty cycle above 6k rpm... The best fix is still the resistor mod (this I have also done myself with 80s/90s analog Toyota tach). Though I'm not sure how the tach circuitry is with the digital AE86 gauge cluster. https://youtu.be/y2TRMWldaQA Quote Link to comment Share on other sites More sharing options...
Adamw Posted January 28, 2021 Report Share Posted January 28, 2021 19 minutes ago, essb00 said: If you would watch sushpants' video about his tach fix, the problem with some tach adapters is that they seem to lose enough duty cycle above 6k rpm... No, I think his problem was he had no aux outputs left so he had the tacho adapter connected to a coil drive, so you only get a very short pulse the length of your dwell setting. If it is connected to an aux output that is set to the tacho function you have full control over the duty cycle and scaling. I have never had any drama achieving a fully working tacho with one of these coil simulator type devices. For me a $25 (or even the $100 8920) adapter is a no brainer, the hours it takes to pull the dash apart, modify it, reassemble, risk of breaking brittle plastic trim clips etc is a last resort. koracing 1 Quote Link to comment Share on other sites More sharing options...
Vaughan Posted January 28, 2021 Report Share Posted January 28, 2021 I modified the tacho in my MR2 a few years ago using the two resistors metioned elsewhere in the forum and that has worked reliably, I imagine it is possible to do a similar thing cheaply to the 86 and other older toyota tachos but it does involve disassembly and soldering Quote Link to comment Share on other sites More sharing options...
Adamw Posted January 28, 2021 Report Share Posted January 28, 2021 He has the "night rider" digital AE86 dash though, where the tacho is a bunch of LED lights. Vaughan 1 Quote Link to comment Share on other sites More sharing options...
ljkayess Posted May 19, 2023 Report Share Posted May 19, 2023 About to get into this exact issue. Can anyone provide confirmation that the tacho booster suggested got the AE86 digi dash to work? Quote Link to comment Share on other sites More sharing options...
DerekAE86 Posted May 19, 2023 Report Share Posted May 19, 2023 2 hours ago, ljkayess said: Can anyone provide confirmation that the tacho booster suggested got the AE86 digi dash to work? I've got a digi dash in mine and the booster works. But I ended up just modding the dash to work directly off the ECU's output. Quote Link to comment Share on other sites More sharing options...
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