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datalogging refresh rates

Practical Reflash Tuning

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Discussion and questions related to the course Practical Reflash Tuning

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You mention in the video that some parameters need to be logged at a rate of 20Hz. That would be every 0.05s, right? I've never seen anything close to that while datalogging. Best I seem to be able to get is 2Hz, and that's only with a few monitors. Is 2Hz even a usable rate? I'm worried I might be missing something critical.

I work on mostly FIATs and Alfas. The most popular scanner software for them is Multiecuscan, which I'm using. I have supposedly the fastest interface available for it (OBDlink SX), and made sure the COM port settings on my laptop are set to 115200bps.

Any suggestions? Is there better software/hardware that supports FCA vehicles I should get instead?

What you want to find is any channels that are "broadcast" on the CAN bus instead of having to request/respond like OBD2. I don't know if your scan tools can be setup to receive this, but it's worth finding out. You will get these for "free" and often they are transmitted at 20 - 100 hz. Due to the request/response, often if you ask for fewer channels, you will get a faster data rate. There are still lots of ECU sthat only respond with data updated every 1-2 hz, which is not really usable for tuning or data analysis.

Forget about OBD-II for any meaningful data logging analysis, it has too slow a response rate to be used.

OBD was not designed for this sort of usage, it was designed for vehicle emissions testing back when a i286 was a fast computer, and hasn't changed much since then. Being a request/response system, rather than a broadcast as CAN is, you only get one channel updated at a time, and if the channel that is being requested hasn't updated since the last request to that channel, you can then have the system pause whilst waiting for the channel to update, rather than going to the next requested channel.

Ok, I'm beginning to understand. Sorry, I'm still learning this stuff.

So I need an interface that will read directly from the CAN bus, and associated software to decode it? I've been googling CAN logging solutions, but I'm not sure what would be appropriate for my needs. Any suggestions?

It's a shame HP Tuners doesn't support the FCA vehicles as they seem to have the most complete solution. Would their VCMscanner still work for the generic parameters?

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