Ok I found this thread and it was very helpful:
http://www.gearhead-efi.com/Fuel-Inj...-OBDII-plug-in

Wiki also shows the PID info here:
https://en.wikipedia.org/wiki/OBD-II_PIDs

So, we know vehicle speed is:
0x4D 0x30 0x31 0x50 0x30 0x44 0x53 0x30 0x31 0x52 0x31 =
M01P0DS01R1=
'M' + HH + 'P' + HH + 'S' + HH + 'R' + H
Where 'M' is for Mode, "HH" is two hex ASCII bytes (e.g. 'F' 'F' for 0xFF). 'P' is for PID, 'S' is for size of PID data reply, and 'R' is for reply count. Note that the 'R' data is a single hex digit (e.g. '2').
= Mode 1 PID 13, get only 1st reply

So for PID 2811 I'm thinking: M01PAFBS01R1 (hopefully 3 hex bytes is not a problem and it still figures the delineation via the S after it for the size packet)
0x4D 0x30 0x31 0x50 0x41 0x46 0x42 0x53 0x30 0x31 0x52 0x31