Perhaps you cant.
Theres been loads of input on this thread, from various models including 147 156 etc
Somebody said that the 147 dial is designed to operate so that it shows 90oC steady when the actual temp fluctuates between 85 and 95
Yes, but that's only for later models with a CAN bus, like 147. The temp as measured by the ECU is processed and sent via CAN to the guage, see