jzxmaniac Posted March 17 Report Share Posted March 17 Hi, I have a 98 JZX100 with a link plug n play ecu. I am trying to get the oem tach working with an aftermarket coil on plug ignition system. The tach is normally powered by a high voltage ignition feedback wire however I no longer have that with the coil on plug setup. i am running out of aux outputs and have the tach currently hooked up to inj 8 output. Is it possible to make that work? I have a tach signal booster installed and have gotten the tach to work but it is very finicky and the rpm needle is constantly bouncing around. I then read that inj outputs don’t have a built in pull up so I tried wiring in a pull up with a 10k ohm resistor (same result) and then with a 1k ohm resistor and it didn’t work at all then. any ideas? Sorry for the long post. Thanks! Quote Link to comment Share on other sites More sharing options...
Adamw Posted March 17 Report Share Posted March 17 What tacho booster do you have? Where are you wiring the pull-up? Quote Link to comment Share on other sites More sharing options...
jzxmaniac Posted March 17 Author Report Share Posted March 17 I’m just using this ebay tach booster: https://www.ebay.com/itm/142171581596?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=UnShSJedRjW&sssrc=4429486&ssuid=LBScgMxOT2m&var=&widget_ver=artemis&media=COPY and I put one end of the resistor to 12v and the other went to the tach booster input side (signal from ecu). Quote Link to comment Share on other sites More sharing options...
Adamw Posted March 18 Report Share Posted March 18 I have used that same booster with other toyota's successfully. From memory it has a pull-up built in on the input side anyway but Im not sure why the 10K worked, but not the 1K, either should be fine and I wouldnt expect those to change the signal that the booster sees at all. Unfortunately hard to diagnose without a scope connected to confirm waveforms etc. You could possibly use the triggerscope as a tool by running a jumper wire from the tacho into trigger 1. Did you try larger duty cycle in the tacho settings? Quote Link to comment Share on other sites More sharing options...
jzxmaniac Posted March 18 Author Report Share Posted March 18 Good idea I will try that with trigger scope. I was seeing the voltage coming off the inj 8 output was very low around 150-200mV. Does that sound right? And yes I did try changing the duty cycle with no real difference. thanks for your help so far side note totally different question. why would my Link CAN gauge read -0.7 to -0.8 psi MAP with ignition on and the car off? On my laptop MAP shows around 101kpa or in imperial it shows 14.7psi, neither of which seem to match the -0.8 psi MAP. Not that it’s a big deal, I just want to be able to trust the MAP reading while driving. Quote Link to comment Share on other sites More sharing options...
koracing Posted March 18 Report Share Posted March 18 What is your BAP reading at the same time in the ecu (barometric absolute pressure)? I think some of the labelling in the gauge could be better because if you're seeing a negative MAP value then something is definitely wrong. Only MGP should show negative values. MGP is BAP-MAP. Quote Link to comment Share on other sites More sharing options...
jzxmaniac Posted March 18 Author Report Share Posted March 18 I’m guessing the reading its showing a map reading of map-atmospheric pressure because it shows around -8 psi at idle and goes to 15psi at WOT. I just figured it was odd that it wasnt reading 0 with the car off. I’m more or less at sea level and bap was 101kpa according to the ecu. bottom left of gauge. Unfortunately I took this with the car running but I will take another one with it off later to show you what I mean Quote Link to comment Share on other sites More sharing options...
Vaughan Posted March 18 Report Share Posted March 18 9 minutes ago, jzxmaniac said: bottom left of gauge. Unfortunately I took this with the car running but I will take another one with it off later to show you what I mean The PSIG means Gauge pressure in psi which is absolute minus barometric If you are seeing a negative value with the car off you will need to look at what your absolute and Barometric values are to make sure they are set up right, a drifting calibration can be indicative of a failing sensor Quote Link to comment Share on other sites More sharing options...
jzxmaniac Posted March 18 Author Report Share Posted March 18 Ok that’s what I thought. I will take a pic of it tomorrow but on my laptop map said 101kpa and bap was about the exact same. It’s just using the map sensor built into the ecu which is nearly brand new. Seemed like to me the reading on my laptop and the reading on the CAN gauge didn’t exactly match which is why I was confused. When I switched it to psi on the laptop it still reads in absolute so it was around 14.6 psi so I was confused where it was getting the -0.7 to -0.8 reading on the gauge. Quote Link to comment Share on other sites More sharing options...
Adamw Posted March 19 Report Share Posted March 19 Im pretty sure if MAP is set to kpa units on the gauge it will display correctly. With it set to Psig they just put a fixed -14.7psi offset on MAP, they dont actually use the BAP value. Quote Link to comment Share on other sites More sharing options...
shane110 Posted April 13 Report Share Posted April 13 Did you get sorted with tacho what did you have to do ? Quote Link to comment Share on other sites More sharing options...
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