UDS Protocol - Long term adaptation of mixture formation not available

   #1  

dynamike

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I got a Q7 from 2011 that runs on UDS protocol. I'm looking to read out long term and short term fuel trim but the following three option are not (!) available to me under advanced measuring values.

IDE00597 - Long term adaptation of mixture formation bank 1
IDE00604 - Short term adaptation of mixture formation bank 1
IDE01869 - Long-term fuel trim bank 1 at idle

Any help would be much appreciated.



Code:
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Address 01: Engine (J623-CJGA)       Labels:. 059-907-401-V2.clb
   Part No SW: 4L1 910 401 H    HW: 4L0 907 401 C
   Component: 3.0TDI EDC17  X37 0003  
   Revision: 53X37---    Serial number:               
   Coding: 2A2A4012A52701020000
   Shop #: WSC 31414 790 00001
   ASAM Dataset: EV_ECM30TDI0114L1910401H 001008
   ROD: EV_ECM30TDI0114L1910401H.rod
   VCID: 2809F8A4E2733C77A17-807C
 
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   #2  

Uwe

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Uhm... That's a diesel. The concept of "fuel trim" doesn't really apply to them.

Gasoline engines control power by controlling the airflow. The engine management then supplies an appropriate amount of fuel, with a feedback loop that "trims" the amount of fuel injected to keep the mixture stoichiometric. Bottom line: The pedal controls the throttle, which controls the amount of air the engine can ingest.

Diesels control power by controlling fuel flow. The pedal controls the amount of fuel injected. In days gone by, diesels just allowed air to flow freely and ran quite lean at partial loads. However, that produced a lot of NOx emissions, which isn't acceptable anymore. Now you can't just restrict the airflow to a diesel because that would reduce the effective compression ratio, and you'd give up the efficiency, and you might not generate enough heat on the compression stroke to ignite the fuel. So what they do now is to mix incoming air with recirculated exhaust gasses in an attempt to keep the mixture in a range where it will neither produce soot or excessive amounts of NOx, but in the end, they still control power by more-or-less directly controlling fuel flow, so the concept of "fuel trim" simply doesn't apply.

-Uwe-
 
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dynamike

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Thanks Uwe for taking the time to explain in such detail. Much appreciated. All my acquired knowledge evolves around petrol engine.
 
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