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BMS JB4 R specific thread

George Smooth

Drag Race Newbie
Location
South Africa
George, the CANBUS part in the FAQ is a bit interesting. Why would adding another device to the OBD port cause latency? As far as I know it's a broadcast network and other devices will see ALL traffic regardless.

Does it matter what device is connected? Or what the device actually does? Say, I have a Arduino CANBUS Shield (Seeed) connected (not necessarily to the OBD port but to the CANBUS anyway). Would that affect the JB4 in any way?

I am not sure why it causes lag as I do not do the hardware development and only the settings and tuning.

The CANBUS bridges between modules so what you see on the engine side will not necessarily be seen on the cluster side for example so attaching devices on other side of modules will not affect.
 

md2185

Passed Driver's Ed
Location
South FL
I can confirm that you can not run 2 devices simultaneously on the obd.
I have a split obd connector.
Wanted to pull some logs with the vcds while having the jb4 on.
The ecu and engine did not like it at all.
PS: An obd cable extender did not cause any latency issues.
 

vanos

Passed Driver's Ed
Location
Germany
I haven't seen what the JB4 does on the canbus (apart from an early alpha version) but judging from its features, I would say it keeps the ECU busy enough. The ign.timing alone (ign corr 2 3 4 and ign tot 1) is enough to be near the limits of a good data rate. Add then everything else the JB4 wants like current gear, afr and so on...
For example, you could experience knock @4500rpm and get a false reading that it occured @4700rpm because of the delay (clogged bus/ecu).

All in all, do not use obd modules like P3 together with jb4..

Also, for those that are logging with Android. I would use the cable and not a bluetooth connection for best accurancy (timing wise).

0) JB4 query the ECU
1) JB4 fetches value from ECU via canbus
2) JB4 does internal decoding and sends modified value to the serial port
3) Bluetooth module fetches the value from the serial port and relays to bluetooth serial (including additional overhead for connection purposes)
4) Smartphone app receives via bluetooth/serial port and displays the value.

Step 3 can be cut, using a cable only.

@hal, you can use arduino if you want and also connect to the obd bus. Just make sure you are not querying the ECU at high frequency or even better don't query at all.
 

rscott4563

Ready to race!
Location
Australia
I haven't seen what the JB4 does on the canbus (apart from an early alpha version) but judging from its features, I would say it keeps the ECU busy enough. The ign.timing alone (ign corr 2 3 4 and ign tot 1) is enough to be near the limits of a good data rate. Add then everything else the JB4 wants like current gear, afr and so on...
For example, you could experience knock @4500rpm and get a false reading that it occured @4700rpm because of the delay (clogged bus/ecu).

All in all, do not use obd modules like P3 together with jb4..

Also, for those that are logging with Android. I would use the cable and not a bluetooth connection for best accurancy (timing wise).

0) JB4 query the ECU
1) JB4 fetches value from ECU via canbus
2) JB4 does internal decoding and sends modified value to the serial port
3) Bluetooth module fetches the value from the serial port and relays to bluetooth serial (including additional overhead for connection purposes)
4) Smartphone app receives via bluetooth/serial port and displays the value.

Step 3 can be cut, using a cable only.

@hal, you can use arduino if you want and also connect to the obd bus. Just make sure you are not querying the ECU at high frequency or even better don't query at all.

Only problem I see with the logic you are using is that if you are saying the delay introduced due to the processing and various comms protocol conversions is going to affect the speed of say when a knock event is occurred is that if there is a delay then it will be global i.e. it will affect all parameters read and displayed by the JB4 software.

Therefore if the knock occurs at 4500rpm then it will be recorded at the 4500rpm point in the log it's just that you won't see it displayed until a few hundred milliseconds later but the event will be recorded with the correct RPM as they were both recorded from the CANBus datastream at the exact same time.
 

vanos

Passed Driver's Ed
Location
Germany
Only problem I see with the logic you are using is that if you are saying the delay introduced due to the processing and various comms protocol conversions is going to affect the speed of say when a knock event is occurred is that if there is a delay then it will be global i.e. it will affect all parameters read and displayed by the JB4 software.

Therefore if the knock occurs at 4500rpm then it will be recorded at the 4500rpm point in the log it's just that you won't see it displayed until a few hundred milliseconds later but the event will be recorded with the correct RPM as they were both recorded from the CANBus datastream at the exact same time.

What you are saying would be true, if every message received by the JB4 contains both RPM and KNOCK.
 

rscott4563

Ready to race!
Location
Australia
What you are saying would be true, if every message received by the JB4 contains both RPM and KNOCK.



But it does doesn't it? Every message on the CAN line will include all data on every address the BMS hardware is actively reading it's just that when there isn't knock the address will be reading a null value either as a binary 0 or if it's actually reading the knock sensor voltage then it will be a value lower than the limit set for registering it as knock.

Isn't the point that every thing being transferred from the CAN network to the JB4 will be subject to the same level of introduced lag/delay on every read cycle?

If I'm off the mark I'm happy to learn and be corrected if you have actual knowledge of the comms protocol and how it is read by an external device.


Sent from my iPhone using Tapatalk Pro
 

vanos

Passed Driver's Ed
Location
Germany
But it does doesn't it? Every message on the CAN line will include all data on every address the BMS hardware is actively reading it's just that when there isn't knock the address will be reading a null value either as a binary 0 or if it's actually reading the knock sensor voltage then it will be a value lower than the limit set for registering it as knock.

Isn't the point that every thing being transferred from the CAN network to the JB4 will be subject to the same level of introduced lag/delay on every read cycle?

If I'm off the mark I'm happy to learn and be corrected if you have actual knowledge of the comms protocol and how it is read by an external device.


Sent from my iPhone using Tapatalk Pro

No, it does not. Every message does not include all data BMS is requesting.
Feels a bit childish saying I did this and that but here you go, I developed this :D
https://www.youtube.com/watch?v=4_X-vregqpU
aaand this
https://www.youtube.com/watch?v=m8SzfXNR904

Anyway, I posted just to inform you guys that obd-readers with jb4 is not a good idea. You do as you like :)

sorry to interrupt or to retract but how are you guys gettin knock and or worried bout knock

RmayT

Knock was just an example.
 

rscott4563

Ready to race!
Location
Australia
No, it does not. Every message does not include all data BMS is requesting.

Feels a bit childish saying I did this and that but here you go, I developed this :D

https://www.youtube.com/watch?v=4_X-vregqpU

aaand this

https://www.youtube.com/watch?v=m8SzfXNR904



Anyway, I posted just to inform you guys that obd-readers with jb4 is not a good idea. You do as you like :)







Knock was just an example.



Hey don't feel childish at all. Everyone here should be here to learn something new and if someone comes along with new information or better knowledge it benefits everyone. [emoji106]

So the question now is when do we get to see JB4 integration with the DIS??
L


Sent from my iPhone using Tapatalk Pro
 

vanos

Passed Driver's Ed
Location
Germany
Hey don't feel childish at all. Everyone here should be here to learn something new and if someone comes along with new information or better knowledge it benefits everyone. [emoji106]

So the question now is when do we get to see JB4 integration with the DIS??
L


Sent from my iPhone using Tapatalk Pro

:) My guess is as good as yours but I would say.. never! On the other hand, they have the cool app where you can change JB4 settings.
 

md2185

Passed Driver's Ed
Location
South FL
Hey don't feel childish at all. Everyone here should be here to learn something new and if someone comes along with new information or better knowledge it benefits everyone. [emoji106]

So the question now is when do we get to see JB4 integration with the DIS??
L


Sent from my iPhone using Tapatalk Pro

Im sure George will wanna find out how you got the codes for their future firmware release on the JB4;)
 

Sa-Gti2

Passed Driver's Ed
Location
SA
George, post some settings to get to 350Whp and 500NM. Supporting mods are TBE, Cooler and Intake.
 
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