First, be aware that the client-side framerate is capped for a reason: to reduce bandwidth to and from your computer. The higher your framerate, the more times per second the game is updating your screen, which means more data. That said, only do this tweak if your internet connection is pretty solid. It will hurt you more than benefit you to enable this on something like a 32-man ONS pub, while it is great for something like 1on1 DM.

The Tweak

The first step is to open up your UT2004.ini and go to the section titled [Engine.LevelInfo]. Under this section, there should be a field called MaxClientFrameRate (if there is more than one entry of this field, feel free to delete all but one of them). This field controls the maximum online FPS. Feel free to set this as high as you want (set it to 0 for no limit) but keep in mind that higher framerate = more bandwidth. I have mine set at 170, which is double the regular framerate.

Netspeed

However, this is not enough. The max framerate is also tied to your client-side netspeed (if you don't believe me, try setting it to the minimum of 2600, then watching your framerate). As I stated above, since a higher framerate will impact the amount of data through your connection, a higher netspeed is required. A lot of topics on this matter say to simply set your netspeed to 10001. This is not a good idea. Why? Netspeed is the limit beyond which unnecessary (and sometimes necessary, in extreme cases) data will be dropped. Setting your netspeed to 10001 will break the 85-fps limit, but unfortunately since you are sending far more data through your connection, a lot of packets will be dropped. Therefore, the ideal netspeed for us to use is 20000, but the game caps netspeed at 15000, so let's stick with that.

Setup Netspeed

Open up your User.ini and go to the section titled [Engine.Player]. Under this section, there should be a field titled ConfiguredInternetSpeed. Set this to 15000. So are we done? No, for some reason, after a map change your netspeed is reset to 10000. To get around this, make a bind that simply sets the netspeed to 15000. The easiest way to accomplish this is to bind it to your "gl hf" key or something else you will hit at the beginning of every game. The command to change netspeed is simply "netspeed 15000" (no quotation marks). For example, my bind looks like this:

F12=say hfhf | netspeed 15000

*The pipe character denotes multiple commands per bind. Just remember to hit the bind every time a new map loads, and you'll be enjoying high FPS! Notes:

• As I said above, this tweak will significantly increase the bandwidth between you and the server. If you are experiencing lag or packet loss with the tweak on, just turn it off by setting your netspeed back to what it was before.
• You may see a slightly higher ping (by 4 ms or so) on the scoreboard. This is due to the fact that UT2004 pings players by sending to each of them small packets created solely for pinging. If there is more data being sent through the connection, the ping packets take slightly longer to be processed. It is not that huge of a difference, but some people have noticed it.
• AntiTCC and SafeGame track netspeed changes and can kick/ban players who change their netspeed too frequently. Don't bind the netspeed command to your movement keys or to your fire button or anything like that. Bind it to something you will hit once or twice when the map starts, and that's it.