tachtest

#include <Tone.h> //download: https://github.com/daniel-centore/arduino-tone-library

Tone speedtone;
Tone tachtone;
Tone fueltone;

long randNumber;
long tachPulse;

void setup()
{
  tachtone.begin(4); //pin that tach is hooked to(PWM PIN REQUIRED)
  speedtone.begin(11); //pin that speedometer is hooked to(PWM PIN REQUIRED)
  randomSeed(analogRead(0));
}
void loop()
{
 randNumber = random(14400,1   000); // generate random number between 100rpm & 7000rpm
 tachPulse = randNumber/144; // 1 puls per varv
  speedtone.play(100, 0); //frequency, duration(0 usually)
  tachtone.play(tachPulse, 0); //frequency, duration(0 usually)
delay(1000)
}