Q&A Forum
Hi, has anyone encounter problems with elm obd not getting correct rpm on low gears?
is there a solution or can someone recommend a good obd conector for dyno data?
I just read admin is working on it for newer version. Thought it was a hw issue of my elm.
thanks
Hi, which work are you referring to?Note the obd plugin is the best to use for obd.
I refer to this.
- OBD2 support for engine RPM. This will enable automatic gear ratio calculation and slip can be monitored. It will support Bluetooth and USB ELM327 adapters. Bluetooth is very practical here!
- obd plugging does not work on mini for example, or vw uds. at least with my hardware.
I think maybe you misunderstood. Please use the OBD2 plugin (ScanTool). It works in all gear. You need press the "Lock gear ratio" button when you have selected the correct gear. Engine RPM is the calculated from the roller rpm and gear ratio. If you want to test in a different gear, then you need to do the Lock gear ratio again.
@admin this is how we are currently getting our great ratio, however with an automatic transmission I am getting a difference at higher rpm due to converter. So wide open throttle is different rpm at same wheel speed as part throttle.
With an auto gear box and torque converter you need to plot vs speed.
@admin Hmmm I have not even seen speed as an option, I'll have to play around in the software some more. With Plotting over speed how do you get an understanding of what RPM the engine is making torque and Power, or know where to adjust fuel or spark tables?
I know these sound like rookie questions, but I am a rookie on the chassis dyno, always had engine dynos before so it was much easier.
Install the Speed and Distance plugin.
With an auto it is tricky to see the power vs RPM. Most just plot vs speed.
Alternatively you can download the OBD2 plugin (SCANTool) an use a high speed OBD2 adapter, or the CANTool and use a CAN adapter to get high frequency RPM. Then plot HP vs that RPM signal. Use Results vs XXX option to setup which parameter you want to plot against.