finding out the injection pulse width thereafter is the same as that of the conventional operations so that the explanations therefor will be dispensed with by repetition of the above mentioned operations the injection pulse width can be sequentially obtained incidentally the most recent atmospheric pressure conformed corrective value c p which has been found by the above mentioned calculation remains stored in the non volatile ram even after turning off of the key switch the portion shown by the double dot dash line in fig3 and 6 indicates another embodiment of carrying out the filtration process on behalf of the atmospheric pressure conformed corrective value c p in fig3 the atmospheric pressure conformed corrective value calculating section 187f and the multiplier 187g are not directly connected but they are connected through a filtration processing section 187i as shown by the double dot and dash line in the drawing the remaining construction is exactly same as the above mentioned embodiment while there is no difference in the operating flow between fig4 and 5 there is interposed in fig6 step s28 between the step s23 and the step s24 as shown by the double dot and dash line in more detail at the step s28 the filtration processing section 187i which has introduced thereinto an input signal of the atmospheric pressure conformed corrective value c p from the atmospheric pressure conformed corrective value calculating section 187f calculates the current atmospheric pressure conformed corrective value c p i by the filtration process in accordance with the following equation 4 where k is a constant to satisfy a relationship of 0 lt k u2267 1 and c p i 1 denotes a previous.