iOS 8.1.1 Jailbreak not released yet?
Pangu 8 is the only jailbreak method that supported to install cydia on iOS 8 and iOS 8.1 yet. So you have to download pangu 8 mac or pangu 8 windows version to jailbreak any iphone, ipad or ipod. You can use pangu 8 for iOS 8 jailbreak on iphone 5s, 5c, 5, 4s, ipad mini, air, 4, 3, 2 and ipod touch. But if you upgrade your idevice upto iOS 8.1.1, you unable to jailbreak it using pangu8.
Because Apple patched pangu 8.1 jailbreak to update as pangu 8.1.1 jailbreak download. So you haven't any tool for install cydia on iOS 8.1.1 yet. But there is a video about iOS 8.1.1 jailbreak in untethered condition by iH8sn0w. So we can have hopes on that to install cydia on iOS 8.1.1 now. This tool hasn't released to the public yet.