Ben.C Posted February 22, 2023 Report Share Posted February 22, 2023 Hi, I'm finalizing my wiring and I want to be sure what I have planned will actually work. I'm running a B18C in a 6th gen Civic, it's a pure track car, ALL THE FACTORY WIRING IS GONE. I'm running K-series individual coils in wasted spark with a crank trigger only (24-1 tooth pattern). I want to use the 2 unused ignition outputs to drive the factory tacho and speedo. I've inserted both the internal cluster wiring diagram and the cluster specs. The tacho is 2:1 so at 9500rpm I'll need to pulse it at 18KHz. The speedo is pretty vague, not too sure, experimenting maybe required! I'm using a SSR to drive the fuel pump with variable speed with AUX 1 I'm using a relay to drive VTEC with AUX 2 I'm using a relay to drive the RAD fan with AUX 3 AUX 4 is currently unused but I would like to use this as a shift light DI 1 is vehicle speed in IGN 3 will drive the tacho (hopefully) IGN 4 will drive the speedo (hopefully) I'm totally open to changing the allocations, let me know if this won't work. Thanks in advance! Quote Link to comment Share on other sites More sharing options...
essb00 Posted February 22, 2023 Report Share Posted February 22, 2023 Tach driven by Aux 4 instead. Shift light to Ign 3 (active low). Speedometer driven directly by VSS -- Ign 4 unused. Quote Link to comment Share on other sites More sharing options...
Adamw Posted February 22, 2023 Report Share Posted February 22, 2023 5 hours ago, Ben.C said: The tacho is 2:1 so at 9500rpm I'll need to pulse it at 18KHz. RPM = revolutions per minute, not per second. 9500/60 is 158Hz, for 2 pulses per rev that would be 316Hz. I agree with essb00 that a proper aux will be better for the tacho as they have a built-in pull-up, if you used an ign drive you would have to add an external pull-up. A shift light wont need a pull-up as the bulb will act as one. How was the speedo driven originally? It was unlikely connected to the ecu, was the sensor a hall effect or AC? Quote Link to comment Share on other sites More sharing options...
Ben.C Posted February 22, 2023 Author Report Share Posted February 22, 2023 Ah yes, I'm an idiot. My math was way off. I'll do as recommended and use AUX outputs for the speedo and tacho, then use IGN3-4 for grounding a relay to keep it simple. The speedo was driven directly from the VSS in factory configuration. The VSS is 3 wire; 12v power, GND, and signal. The factory service manual says you should see 5v at the signal wire and at the cluster. I'll need to add a voltage regulator to regulate down the AUX 12V signal. The reason I don't want to run the speedo directly off the VSS is because I want the dash harness to remain untouched when I eventually switch to a K-series. I plan to change the ECU to an Extreme G4X and would like to just adjust the ECU settings depending on what K-series transmission I end up with (some use counter shaft speed, some use speed at the differential). Also, as dumb as this sounds...I want gauge sweeps at key on. Some people want crackle and bang tunes, I want gauge sweeps. Quote Link to comment Share on other sites More sharing options...
Adamw Posted February 22, 2023 Report Share Posted February 22, 2023 5 hours ago, Ben.C said: The speedo was driven directly from the VSS in factory configuration. The VSS is 3 wire; 12v power, GND, and signal. The factory service manual says you should see 5v at the signal wire and at the cluster. I'll need to add a voltage regulator to regulate down the AUX 12V signal. The aux is only weakly pulled up to 12V, it can connect directly to the speedo. Quote Link to comment Share on other sites More sharing options...
Ben.C Posted February 22, 2023 Author Report Share Posted February 22, 2023 Ah perfect, Thanks for the help. Quote Link to comment Share on other sites More sharing options...
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