this is a s13 tachometer.
this is a little potentiometer. you can adjust so your stock tachometer will work with a 6 or 8 cylinder engine.
you can make adjust from that hole. BEFORE YOU DO ADJUST, TAKE POTENTIOMETER OHM READING OR MAKE SOME MARKS.
if you have a msd ignition module, you need to put some rpm limiter to a 4000rpm or whatever you want , then make your engine bounce in rev limiter and see if potentiometer needs more adjust. repeat adjust til rpm limiter match rpm in gauge. adjust needs to be done in small steps because this potentiometer is very sensitive.
GND = GROUND ; IGN = 12V FROM THE "ON" KEY SWITCH POSITION ; SIG = TACHOMETER SIGNAL INPUT. SQUAREWAVE FROM YOUR MSD TACH OUT OR IGNITION MODULE TACH OUT.
SPEEDOMETER.
our speedometer uses VSS sensor . its a "ac generator" . you can test with multimeter in ACV and turn gear sensor with your fingers. it will show some ACV in multimeter.
this blue piece is a potentiometer. adjust in same way as tachometer. some little adjust. this will work with a non nissan vss sensor and with bigger or smaller tire size. right now, im running a vss sensor from a t5 transmision. it works fine.
GND = GROUND ; IGN = 12V FROM "ON" KEY SWITCH POSITION ; SIG = 1 PIN FROM YOUR VSS SENSOR. 2ND PIN FROM VSS GOES TO GND ; 2P = VCD OUTPUT . ITS A CONVERSION FROM SPEED TO VOLTS. NO CONNECTED.
idea:
remove potentiometer from speedo so you can do tweak without remove cluster. potentiometer has 3 pins. 2 pins are welded together . so orange wire is welded in the middle pin and side pin. violet wire is welded in the other side pin. dont worry if you weld together middle&left side OR middle&right side in the potentiometer. important thing is weld wires as pictured in pcb.
red dot is place where you need to cut a little of plastic.
if you have some questions about potentiometer and wires in this last pictures, just ask and i will help asap. i have 1 more cluster alone so i can take some more pictures.
if you havent a gps speedo, you can use this web tool to calculate your speed at desired rpm.
http://vexer.com/automotive-tools/speed-rpm-calculator
you can do adjust for a 55mph. just use web tool to know at wich rpm and wich gear u are at 55mph and make adjust in potentiometer.
if you do adjust for a lower speed, it will be less accurate.