Hi. Does anybody know that w108/109 rpm Gauge (7000rpm) works properly on a w115 4 cycl.? We have installed today, but watched that the gauge shows the revolution remarkably less than the normal, even, could never pass 3000 rpm. Is it a fault to install 6 cycl. gauge on a 4 cycl. engine or is there another problem with the gauge?

Thanks in advance..