From DD-WRT Wiki
Despite previous postings and the help info in DD-WRT Web GUI that Afterburner only works on the GS models, this speed-enhancing feature is available on all DD-WRT enabled G routers. It is hardware independent. Afterburner will only improve speeds when used with clients that also have the Speedbooster/Afterburner feature; use with "normal" 802.11g clients will actually lower performance.
- Afterburner can be used in networks that also have 802.11b devices, and will not disable the use of them.
- Afterburner can help in environments dense with wireless signals.
- Many MiniPCI cards built into notebooks and many PC Cards are based on Broadcom chips whose configurations support Afterburner
Afterburner is also known as:
- Turbo G 125mbps
- 125* High Speed
- G Plus
- Xpress Technology
Afterburner is not:
- Super-G / 108 mbps (Super-G is an Atheros technology)
 Check if Your Router Supports Afterburner
- Connect to your router using telnet or ssh. Telnet/SSH and the Command Line
- Type wl cap and press enter. It will return a list of capabilities.
- If afterburner is listed you may enable Afterburner on the Advanced Settings tab under Wireless in DD-WRT.