Version 1.4 Now Available for the APR 2.9T B9 RS4/RS5 ECU Upgrade!

10 min read

Version 1.4 Now Available for the APR 2.9T B9 RS4/RS5 ECU Upgrade!

10 min read

Version 1.4 is now officially available for the Audi B9 RS4 and RS5 2.9 TFSI! This update is recommended for all customers on previous file versions and is available at all APR dealers across the globe. This update brings new features and updates and is free for all existing APR Plus, APR Stage 1, and APR Stage 1+ customers. The following items have changed from version 1.0 to version 1.4:

New Features:

  • Stage 1+ was created to support use of our new High Pressure Fuel Pump (HPFP)
  • Launch control was optimized with a 2-step style limiter
  • Driveline protection was included to protect components upon a launch
  • Auto Start/Stop, a feature on ROW market vehicles, now defaults to the off position
  • Exhaust crackle is now enabled under more scenarios, such as neutral revving
  • Support was added for valveless exhaust systems


  • Cold start RPM oscillation is now addressed
  • Exhaust crackle was disabled on some codes and is now addressed
  • All driveline faults presents on some codes are now addressed


Upon flashing this update, it’s critical all fault codes, which naturally occur during the flashing process, must be cleared before driving. Clearing fault codes resets all adaptation data. A few drive cycles will be necessary for some driving behavior, such as transmission shifting, to return to normal. Exhaust crackle may take up to 5 minutes to function fully for the first time as some exhaust temperature modeling data must accumulate after flashing.


Q: What caused the RPM oscillation during cold start?

A: Catalyst temperature protection was enabling during the catalyst heating routine. This scenario did not cause any harm. The updated corrects this behavior.

Q: Why were there faults on 1.3?

A: The original launch control routine inadvertently disabled the exhaust crackle. This did not cause any harm to the engine. Furthermore, some ECU codes had a threshold that was too low, causing a fault code or driveline malfunction error. This also did not cause any harm to the engine.

Q: What vehicles get Auto Start/Stop and how does this feature work?

A: Non-North American vehicles get Auto Start/Stop. Our feature defaults it to the off position. Pushing the (A) button reenables the feature.

Q: What is the valveless exhaust feature?

A: The factory ECU has an aggressive protection routine that enables when the ECU believes the valves in the mufflers are not working correctly. We physically measured back pressure in the system under full power operation with the valve closed and found the difference to be negligible. Proving this was safe on this platform for a customer with an actual valve issue, we’ve altered setting so the exhaust can be modified and not trigger the power reduction routine.

Q: How do I use the new Launch Control?

A: Video tutorial:

Q: How much is Stage 1+

A: Stage 1+ is the same price as Stage 1. It’s a free upgrade for existing Stage 1 or Plus customers.

Q: How much power does stage 1+ make over Stage 1?

A: We measured a maximum gain of +37 AWHP and +50 AWHP over Stage 1 on E85. Graphs on our website on the ECU and HPFP product page. Gains were ONLY observed on E85. On all other octanes the system has plenty of fueling and does not have room to make more power.

Q: How much do your updates cost?

A: Updates a free. A dealer may charge labor for their time.


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