There are two options for this:
1) Mount the filesystem as ext2, and/or use tune2fs to eradicate the journal:
2) Try setting the journaling mode to "writeback," which will only journal the filesystem metadata, not the actual data:
From a data integrity standpoint, both of these are probably bad ideas. However, if your goal is to write data a little bit faster without much regard for whether or not it will be corrupted after a crash, it might be worth a shot.