03-12-2003, 07:58 AM
View Full Version : Does the HEX-COM allow a higher sampling rate than ISO-COM?
03-12-2003, 07:58 AM
03-12-2003, 02:03 PM
<ul><li><a href="http://autos.groups.yahoo.com/group/VAG-COM/message/11310">Read More Here</a></li></ul>
03-13-2003, 04:40 AM
03-17-2003, 10:10 PM
OK, let's go over this stuff again:
If you're looking for better sample rates, the first thing you should do is go to the Options Screen:
<A HREF="http://www.ross-tech.com/vag-com/tour/option_screen.html" TARGET="_blank">http://www.ross-tech.com/vag-com/tour/option_screen.html</A>
Make sure Blk_Int is set to 25, Char_Int is set to 0, and neither of the "Reduce CPU Usage" boxes are checked. Then click SAVE. If you haven't done this, your sample rate will suck.
Now, all 2.7T's are Bosch ECU's running the older KW1281 protocol. As I've mentioned before, Bosch implemented the KW1281 protocols in it's ECUs in a totally brain dead way. There's no way to get a more than one new character every ~10mS from these ECUs. So despite the fact that they run at 10,400 bits / second, the *effective* data rate is only about 1 kbps. Are any of you people old enough to have used a 1200 baud modem? That's roughly how Bosch has got these ECUs "throttled" when it comes to sample rates with the VW protocol. There's nothing any scan tool can do to speed this up -- something between 3 and 4 samples per second looks like the absolute limit. Somewhat strangely, the older M5.9 (cable throttle) ECUs seem to be a little faster than the newer ME7 (Drive-By-Wire) boxes.
This problem is not limited to 2.7Ts, it's all Bosch ECUs running KW1281 -- in other words almost all US-model engines, except some 2002+ stuff. If you've got a 2002+ 3.0 or 1.8T (Audi A4 and Passat only, not Golf/Jetta, etc) which uses KWP2000, then it's possible to get *much* faster sample rates -- up to 10 samples/second with a HEX-COM.
HEX-COM vs. TWIN-COM (actually HEX-COM vs. all "dumb" interfaces):
The HEX-COM will get you a somewhat faster sample rate than a dumb interface. How much faster? It really depends on how the protocols are implemented in the control module you're talking to. Figure a 20-40% improvement on averge -- but I make no guarantees on this, there are simply too many variables, including the PC you're running on, the version of Windoze, etc, etc.