Serial OBD data resolution

[Xavier]

After upgrading to 4-cam Video 4, I've placed one of the two addicional cameras in the foot area, to see how good -or bad- I'm playing with the pedals.

With the new video information, I've confirmed what I've previously suspected: throttle position and RPM data isn't really acurate, specially the first one that, for exemple, remains constant when I'm doing fast heel & toe gear reductions.

Additionally, I can see some data delay between throttle position data and pedal position in the video, about half a second.

I've ckecked Video-4 data configuration, both storage and serial output are set to the maximum rate.

Is this a SerialOBD limitation or am I missing something ?

Regards.

[Support]

Serial OBD can be quite slow to update - it really depends on the car. For RPM I would recommend a direct connection ot the car if at all possible.

Thanks,

support

[midlana]

Are you saying that rpm is not accurate at all, or that it is accurate but delayed?

[Support]

accurate but slow... if you turn off all RPM filtering, you will see the updates as they "arrive".

Thanks,

Support

[osborni]

Most driver input data (brake, throttle, steering) should be recorded at a 10-20hz rate. Stuff like engine pressures and temps do fine at 10Hz. Faster or bigger swinging stuff like AFR or EGT should probably be at 25-50Hz.

All of that is typically MUCH faster then what a serial OBD bus can provide.

Probably better off tapping into the TPS for direct measurement of throttle and an independent pressure sensor for brakes and a string pot (or something) for steering.

The engine criticals are probably just fine for OBD speeds. Temps and Pressures don't move that fast and you're really just monitoring them for issues and diagnostics, not for direct driver feedback. Still should have pressure and temp guages (if you don't have a digital dash) to monitor that stuff anyway.

But then you cold just look at the side by side video for different laps to see where you are on the track and when you are making inputs into the car.

[Xavier]

Thanks for the replies, guys.

RPM data comming from Serial OBD isn't as bad as throttle position. During heel & toe, RPM is more less in concordance with my foot movements, but throttle position curve remains almost plain.

Maybe CAN OBD provides better data update rates than Serial, but unfortunately my car don't support the first.

I should consider some analog sensor for throttle, but not as easy as it seems on an electronic one...

Regards.

[osborni]

Your car has a TPS? Yes? If it has EFI, then 99% sure it has a TPS. You can just tap into the sensor output for your logger (DL1?)

I'm assuming you do since you have a car with an OBD system in it, hence efi.