There has been a lot of mis-information on the web about exactly how the S13 gauge cluster operates. Hopefully this article clear things up.
First of all, everyone that said 2k, 4k or 8k ppm for the gauge cluster is wrong. 60Hz AC sine wave, ~3V p-p into Y/L with Y/B grounded gave me 13mph. This means the gauge cluster needs 16,000 pulse per mile by the following calculation:
60Hz * 3600 sec/hour * 13 mile/hour = 16,000 pulse / mile
You also don’t really need a Dakota Digital box, unless you like to blow $70. Reason being the LS1 ECU can be configured using HP tuners to give the correct 16,000 PPM output. (VSS Output Pulses per mile)
However, the LS1 ECU send out a DC square wave, 12v p-p. It looks like this:
The s13 gauge cluster needs to see 0 crossing on the Y/L line. Instead of using a dakota digital box, go to radio shack and build this.
The circuit is not all that complicated. I crammed it all together, put some heatshrink tube around it and tied it into the main dash harness.
Voila! Although it is not a perfect sine wave, the s13 gauge cluster will happily give you an output using the following waveform.