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Title: Understanding Short Term and Long Term Fuel Trim Post by: userpike on May 17, 2013, 12:59:41 AM This is a good explanation. First part is lecture and last 10 minutes is live demonstration.
http://youtu.be/oRX2V6_a3dc enjoy! Title: Re: Understanding Short Term and Long Term Fuel Trim Post by: IamwhoIam on May 17, 2013, 03:47:44 AM What he fails to understand, or maybe it's different on US cars, is that short term is an additive correction, long term is multiplicative. Otherwise it's not a bad explanation.
Title: Re: Understanding Short Term and Long Term Fuel Trim Post by: nyet on May 17, 2013, 07:56:33 AM What he fails to understand, or maybe it's different on US cars, is that short term is an additive correction, long term is multiplicative. Otherwise it's not a bad explanation. I don't think that is true... idle correction is additive (both long and short), part correction is multiplicative (long and short)... AFAIK anyway Title: Re: Understanding Short Term and Long Term Fuel Trim Post by: elRey on May 17, 2013, 09:03:21 AM Great video .
Title: Re: Understanding Short Term and Long Term Fuel Trim Post by: julex on May 17, 2013, 11:41:18 AM I am having prolem with VCDS... what is the unit it display short term additive trims? % doesn't make sense, shouldn't it be in ms?
Title: Re: Understanding Short Term and Long Term Fuel Trim Post by: phila_dot on May 17, 2013, 11:52:08 AM I am having prolem with VCDS... what is the unit it display short term additive trims? % doesn't make sense, shouldn't it be in ms? Percentage of fuel mass rk_w (relative fuel mass) gets translated to on time in RKTI Title: Re: Understanding Short Term and Long Term Fuel Trim Post by: julex on May 19, 2013, 06:30:40 AM Thanks.
What's the upper threshold (load, rpms?) for RKAT/RKAT2 being active? Title: Re: Understanding Short Term and Long Term Fuel Trim Post by: phila_dot on May 19, 2013, 07:27:27 PM RKAT
------- ml_w <= 25 kg/h (NO1) nmot_w <= 1000 rpm (MLO1) RKAZ ------- rl_w >= 24% (RLU3) <= 48% (RLO3) ml_w <= 90 kg/h (MLO3) nmot_w >= 1800 rpm (NU3) RKA ------- rkat_w * (640/nmot) + rkaz_w The 640 is N0 and nmot is really max(nmot, NRKAB), but NRKAB is 400 rpm. Title: Re: Understanding Short Term and Long Term Fuel Trim Post by: phila_dot on May 19, 2013, 07:54:04 PM FRAU
------- ml_w >= 35 kg/h (MLU2) <= 250 kg/h (MLO2) rl_w >= 20.25% (RLU2) <= 99.75% (RLO2) FRAO -------- ml_w >= 300 kg/h (MLU4) rl_w >= 75% (RLU4) Title: Re: Understanding Short Term and Long Term Fuel Trim Post by: phila_dot on May 19, 2013, 08:31:23 PM What he fails to understand, or maybe it's different on US cars, is that short term is an additive correction, long term is multiplicative. Otherwise it's not a bad explanation. I don't think that is true... idle correction is additive (both long and short), part correction is multiplicative (long and short)... AFAIK anyway Short term fuel trim (fr_w) is multiplicative. Long term fuel trim is additive (rka_w) and multiplicative (fra_w). Title: Re: Understanding Short Term and Long Term Fuel Trim Post by: julex on May 20, 2013, 06:30:41 AM Thanks for the thresholds!
Title: Re: Understanding Short Term and Long Term Fuel Trim Post by: ABCD on June 02, 2013, 08:38:08 PM Short term fuel trim (fr_w) is multiplicative. Long term fuel trim is additive (rka_w) and multiplicative (fra_w). If i understand correctly, fr_w which is output of lambda controller isa called short term part. Thanks. Title: Re: Understanding Short Term and Long Term Fuel Trim Post by: bomby on June 10, 2013, 12:09:07 PM and how to interpreter the value of FR_W? cause i see only values around 1
Or is there an other variable to log and see the actual percentage like you see in the measure blocks like vcds of the actual current sort fuel trim? Pieter-Jan Title: Re: Understanding Short Term and Long Term Fuel Trim Post by: phila_dot on June 10, 2013, 01:53:14 PM and how to interpreter the value of FR_W? cause i see only values around 1 Or is there an other variable to log and see the actual percentage like you see in the measure blocks like vcds of the actual current sort fuel trim? Pieter-Jan fr is the same variable that you see in block 33. To veiw it as a percentage: (fr-1)*100 |