Issues with data logging on JDM ECU
Posted: Tue Jul 01, 2025 1:31 am
Hello! I'm new to the open source tuning world, so apologies if some of this should be obvious. And if there's a manual to read, I'm happy to RTFM so please feel free to link me to docs. 
My setup:
When I start logging from FastECU the RPM shows in single digits. It looks approximately like it's being divided by 250 or so. i.e., when the car settles down to warm idle it hovers around "3 RPM" when I'd expect the engine speed to be around 700-750RPM. I see up to "7 RPM" on initial startup (which would correspond to 1750RPM, which looks about right judging from the tach). The latest BtSSM version seems to log RPM accurately. I'd love to do logging directly from FastECU though. I was debating just editing the logger XML until I guessed the "right" conversion factor, but if there's other parameters that are somewhat off I might not notice at a glance so I'd like to get to the bottom of this mystery.
Should I grab different ECU & logger definitions? Could this be some weirdness specific to this ECU? Am I holding it wrong?
My setup:
- 2005 USDM Legacy GT 5spd
- 2004/2005 EJ20Y with stock TD04HLA turbo
- AVO twin scroll catted downpipe + modified 2015 WRX catback exhaust
- ECU from 2005 JDM Legacy GT 5spd: Part number 22611AK223, Internal ID string in the dump of the tune: A2WD012B
- Tactrix Open Port 2.0
- Dumped the immobilizer EEPROM on my USDM ECU and flashed it to the JDM ECU (status: works, starts up)
- Installed iWire exhaust AVCS harness (status: works, no CELs)
- Dumped the tune from the JDM ECU (status: looks good, same MD5sum as: https://github.com/bludgod/RomRaider/bl ... acy-GT.hex)
- Using definitions from here: https://github.com/TD-D/SubaruDefs/tree/Stable
- ECU defs: https://github.com/TD-D/SubaruDefs/blob ... u_defs.xml
- RomRaider Logger File: https://github.com/TD-D/SubaruDefs/blob ... STD_EN.xml
- ECUFlash Definition Files Directory: https://github.com/TD-D/SubaruDefs/tree ... 20standard
- (All other FastECU config values left at defaults)
When I start logging from FastECU the RPM shows in single digits. It looks approximately like it's being divided by 250 or so. i.e., when the car settles down to warm idle it hovers around "3 RPM" when I'd expect the engine speed to be around 700-750RPM. I see up to "7 RPM" on initial startup (which would correspond to 1750RPM, which looks about right judging from the tach). The latest BtSSM version seems to log RPM accurately. I'd love to do logging directly from FastECU though. I was debating just editing the logger XML until I guessed the "right" conversion factor, but if there's other parameters that are somewhat off I might not notice at a glance so I'd like to get to the bottom of this mystery.
Should I grab different ECU & logger definitions? Could this be some weirdness specific to this ECU? Am I holding it wrong?