1998 gauge cluster - Holley Dominator
11-13-2015, 11:05 PM
#21
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I was hoping Soundengineer was going to chime in again since it seems like he had first hand experience with this scenario.
11-24-2015, 07:23 PM
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Ok trying to wrap this project up, any tricks on getting the tach to read right? Mine is currently reading double the engine rpm according to the holley software.. been poking around and trying to figure out if there is a way to halve it.. but no luck. Ideas?
11-25-2015, 05:46 PM
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You can get a signal off one side of the coil harness. I believe the coils have constant + while the negative side is triggered as each coil fires. If you tap into the ground that feeds all the coils, it would be similar to tapping the negative side of the coil, like on an old SBC.
This is just pure conjecture on my side, but it might be worth researching further to make sure I am on the right track.
Andrew
11-26-2015, 09:12 PM
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The stock tach is looking for a 4 cylinder signal, while the Holley is sending an 8 cylinder signal, hence the double reading. I don't think this can be changed in the Holley software without effecting the operation.
You can get a signal off one side of the coil harness. I believe the coils have constant + while the negative side is triggered as each coil fires. If you tap into the ground that feeds all the coils, it would be similar to tapping the negative side of the coil, like on an old SBC.
This is just pure conjecture on my side, but it might be worth researching further to make sure I am on the right track.
Andrew
You can get a signal off one side of the coil harness. I believe the coils have constant + while the negative side is triggered as each coil fires. If you tap into the ground that feeds all the coils, it would be similar to tapping the negative side of the coil, like on an old SBC.
This is just pure conjecture on my side, but it might be worth researching further to make sure I am on the right track.
Andrew
AFAIK the tach uses a 12v square wave, in stock application its looking for a 2pulse per revolution, and the holley is outputting 4 pulses per revolution, since its using a 12v signal (right?) would setting up a PWM output work and reference RPM as the output?
I have the screen pulled up now, and its asking for 2 axis, what would the other one be??
12-02-2015, 03:42 PM
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), but it is where it is supposed to be. I'll get my car warmed up and take it for a spin and see if its reading 100%, and see if I got my speedo working now that I got my hands on the J4 connector from Mouser Electronics and transferred the VSS wires to it.Here is a screenshot of the PWM+ output that seems to have gotten it working, note that it seemed to responded faster IMO at 80% as compared to 25.. not much but a little bit, if you increased it past say 85 it actually reved in reverse (tach dropped to 0 instead of jumping to say.. 2000rpm) so once we get it out and about might have to drop it lower than 80 .. maybe 65-75%.
