CAN ID for RPM

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Bentleytrackboys

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Hi

Stab in the dark, but does anyone know the CAN id that shows the RPM on a 2004 Bentley Continental GT

Thanks,
Louis
 
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Uwe

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A 2004 Bentley doesn't do diagnostics via CAN -- it's all K-Line. So if you wanted to see CAN messages with RPM, you'd need to tap into the powertrain CAN bus somewhere. In fact, the same is true of just about every other VAG product, even the ones that do diagnostics via CAN. With one exception, the CAN bus at the diagnostic connector is a "blind" bus that only goes to the car's Gateway, which in turn acts as a firewall. The only want to get RPM at the diagnostic connector is to make individual requests of Measuring Block or Value that has RPM. If you just want to passively listen for RPM, you still have to find and tap into the internal CAN buses.

The exception is the B7 A4 Audi (and the its SEAT sibling). Those cars didn't have a Gateway and had the Powertrain CAN bus right on pins 6 and 14 of the diagnostic socket.

-Uwe-
 
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Bentleytrackboys

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Hiya,

Yeah we’ve bought a ECUMaster CAN to USB device and tapped into the Canbus, we’ve got the software that shows us the active CAN signals and hexadecimal bytes, so just been testing it by using throttle and looking to see if there’s any noticeable changes in the ID values.
 
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NEtech

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You can post 2 CAN trace logs here, one with Ignition ON and one with engine at idle.
 
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NEtech

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Is "20230526_1504_engineIdle.trace" at idle 100% of the time?
Some condition change 2/3 from the beginning.
If idle is first after 2/3 time, then one Rpm is CAN id 280 Byte 3 (MSB) + Byte 2 (LSB) div 4.

id280.png
 
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Bentleytrackboys

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Is "20230526_1504_engineIdle.trace" at idle 100% of the time?
Some condition change 2/3 from the beginning.
If idle is first after 2/3 time, then one Rpm is CAN id 280 Byte 3 (MSB) + Byte 2 (LSB) div 4.

id280.png
Cheers, got that working. What's the software you're using to view the logs, next on our list to identify is:

Fuel Level
Speedometer
Water Temperature
EML
 
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NEtech

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I guess Water Temperature is id 0x420 Byte 4 (Byte 0 is first from left).
It is a program I am making.
 
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Bentleytrackboys

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I guess Water Temperature is id 0x420 Byte 4 (Byte 0 is first from left).
It is a program I am making.
That seems to be working ;) Would love to pick your brains and software recommendations for reverse engineering the Bentley CanBUS system.

Finding what gear the car is in, is our next main challenge. But the software we use isn’t very good for data logging from the can.

Any pointers?

Thanks
 
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NEtech

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I guess it should be easy (if it is available), make a log, from neutral, through all gears and back through all gears, ending in neutral.
 
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Bentleytrackboys

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I guess it should be easy (if it is available), make a log, from neutral, through all gears and back through all gears, ending in neutral.
Hi,

Please find log file of car running, starting in neutral and then going from 1st to 6th gear and then back from 6th to 1st and ending in neutral.

https://filebin.net/5d1kd04krx0hwwux

Thanks,
Louis
 
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NEtech

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CAN id 0x440 Byte 1 Bit 0..3 (From left), Source vw_golf_mk4.dbc commaai GitHub.

id440.png
 
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Bentleytrackboys

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CAN id 0x440 Byte 1 Bit 0..3 (From left), Source vw_golf_mk4.dbc commaai GitHub.

id440.png
So looking at our side, here are the numbers we're getting for the gearings on 440A

P - 128
R - 119
N - 96
D - 81
D - MANUAL 1 - 225
D - MANUAL 2 - 226
3 - MANUAL 3 - 227
4 - MANUAL 4 - 228
5 - MANUAL 5 - 229
6 - MANUAL 6 - 232

I think our ECU Master ADU is looking for 'he value of a displayed gear is -1 for the reverse gear, 0 for the neutral gear, 1 for the first gear, etc., respectively.'
 
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Bentleytrackboys

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gearsecu.png


Just messing about with the byte positions and extracting bitfields at the moment, any guesses?
 
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Bentleytrackboys

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gearscan1.png


Been playing around with it, closest I've got it using the following configuration:

P - 0
R - 7
N - 0
D - 1
D - MANUAL 1 - 1
D - MANUAL 2 - 2
3 - MANUAL 3 - 3
4 - MANUAL 4 - 4
5 - MANUAL 5 - 5
6 - MANUAL 6 - -8


CAN id 0x440 Byte 1 Bit 0..3 (From left), Source vw_golf_mk4.dbc commaai GitHub.

id440.png
 
   #17  

Bentleytrackboys

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CAN id 0x440 Byte 1 Bit 0..3 (From left), Source vw_golf_mk4.dbc commaai GitHub.

id440.png
Managed to get the gear indicator working now, using custom functions to match the ID’s given to the Gear indicator letters.

Now moving onto Fuel Level, Speedometer, and EML.

We have a log from when EML was off, and EML is on now. Would it be easy to identify the change using your software?

Thanks,
Louis
 
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