Can anyone tell me the Enchantment Id for the longhammer?

I have no idea what you're talking about but if you look http://uesp.net/wiki/Skyrim:Items you can find all item ID's there.

he's talking about the speed of the longhammer (two handed warhammer), which is as fast as a one-handed waraxe.
i don't think it's an enchantment, though, because you can enchant it like a regular item.

It's not an enchantment.

The weapon speed just has a different setting. When the CK comes you will be able to easily change the speed of any weapon, assuming it works like it did in the CS for MW and OB.

Is in not faster because it has a lower weight than standard but still has near the same hit power?

Interesting idea, but I don't think weight is the determining factor for speed. If it was then those two handed axes you can find in the Labrynthian would be uber, since they only weigh 5.

no, weight doesn't influence damage or speed in any way. maybe they influence stagger - have to test that with the labyrinthean weapons - but it's just a guess.

Here's a thread dedicated to the longhammer: http://www.gamesas.com/topic/1340172-best-2h-weapon-the-longhammer/page__fromsearch__1

does it occasionally hit 2-3 times but lower damage? more hits means more tp, more weapon skills. lower dmg cap means lower weapon skill damage though which at least in my opinion evens out, may even get you killed drawing hate with nothing close to a death blow. when it comes to DPS though everyone has an opinion.