Well what you can do is increase the starting size and the target size, then also the emit amount. Messing around with the settings would probably be the best thing to do if you are trying to create a massive flame. i could tell you how, but you might want yours different Hope this helps out at least a little.
Just fyi, "massive" flames intended to cause lag to others are strictly forbidden as far as I know, would also cost you a shitload of tc and annoy the shit our of other players thus giving you a shitty reputation.