As outlined earlier, diesel engines rely on the
temperatures at the end of the compression stroke to be
high enough to ignite the injected fuel. Since the autoignition
temperature of hydrogen is significantly higher
than diesel fuel, it is not easily reached with conventional
compression ratios. Therefore, hydrogen is better suited
for spark ignition operation rather than compression
ignition, although the latter is not impossible and can have
its advantages, as explained in Section V-C.