improves significantly as the combustion chambers heat up a similar result as for fig5 and fig6 is also valid for the nox emissions fig7 and fig8 show a glowplug control algorithm according to the application fig7 illustrates an activation of a glowplug it also refers to the activation of several glowplugs which may be activated simultaneously or sequentially in decision steps 60 it is tested whether the crankshaft revolution speed is between a lower threshold v1_on and an upper threshold v2_on if this is the case it is tested in a further decision step 61 if the fuel intake is between a lower threshold q1_on and an upper threshold q2_on if the crankshaft revolution speed and the fuel intake lie in the respective ranges a timer is started in step 62 otherwise decision steps 60 61 are repeated after start of the timer it is again tested in decision steps 63 and 64 if the crankshaft revolution speed and the fuel intake lie in their respective ranges if this is the case it is tested in decision step 65 whether an activation time t_activate has been reached otherwise the timer is reset in step 67 and the algorithm loops back to decision step 60 if in decision step 65 it is determined that the activation time has been reached the glowplug is activated in step 65 otherwise the algorithm loops.