benyeats wrote:
Beaten to it. The 'USB' OBDII loggers are using USB in its serial port emulation mode.
That may or may not be an issue. The advantage to this is that Windows has built-in drivers for common USB/serial chipsets. So if you plug the device into a different PC, you get an automatic driver install, rather than having to hunt for the driver disc that came with the gizmo.
And just because it appears to the host as a serial port, doesn't mean it is limited to RS-232 speeds. The
FTDI FT2232H (which just happens to be the first chip I thought of) can do serial speeds up to 12Mbit/sec (that's 20% faster than original Ethernet) or if used in other modes, up to 8 Mbyte/sec.
OBDII has been around since approx the early 90s and the ECU in the Atom (any version) likely has its roots in many years old electronics.
As for it being slower than the real time signals that the dash gets / throttle pedal generates of course it is!
Depending on which particular OBDII signalling system is used by a car, you will get faster or slower data at the OBDII connector. The high-speed CAN bus on the Ecotec operates at 500Kbit/sec. Unfortunately, Brammo didn't connect it to the OBDII port on any Atom I've seen, but it is relatively easy to do so - you need to run a twisted pair of wires from the ECU to the OBDII port. (Brammo "stole" the existing CAN wires in the harness for the Masterlube power).
Remember, almost the entire dash of the Cobalt SS / ION Red Line that this engine was intended for run off the CAN bus. The only 2 exceptions that I've found are the boost gauge and the Check Engine Light.