Pages: [1]
Author Topic: Understanding Short Term and Long Term Fuel Trim  (Read 10091 times)
userpike
Hero Member
*****

Karma: +22/-1
Offline Offline

Posts: 763


« 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!
Logged
IamwhoIam
Hero Member
*****

Karma: +52/-115
Offline Offline

Posts: 1070


« Reply #1 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.
Logged

I have no logs because I have a boost gauge (makes things easier)
nyet
Administrator
Hero Member
*****

Karma: +608/-168
Offline Offline

Posts: 12270


WWW
« Reply #2 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
Logged

ME7.1 tuning guide
ECUx Plot
ME7Sum checksum
Trim heatmap tool

Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your ex
elRey
Hero Member
*****

Karma: +32/-1
Offline Offline

Posts: 565


« Reply #3 on: May 17, 2013, 09:03:21 AM »

Great video .
Logged
julex
Hero Member
*****

Karma: +79/-4
Offline Offline

Posts: 923


« Reply #4 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?

Logged
phila_dot
Hero Member
*****

Karma: +173/-11
Offline Offline

Posts: 1709


« Reply #5 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
Logged
julex
Hero Member
*****

Karma: +79/-4
Offline Offline

Posts: 923


« Reply #6 on: May 19, 2013, 06:30:40 AM »

Thanks.

What's the upper threshold (load, rpms?) for RKAT/RKAT2 being active?
Logged
phila_dot
Hero Member
*****

Karma: +173/-11
Offline Offline

Posts: 1709


« Reply #7 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.
« Last Edit: May 19, 2013, 07:32:45 PM by phila_dot » Logged
phila_dot
Hero Member
*****

Karma: +173/-11
Offline Offline

Posts: 1709


« Reply #8 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)
Logged
phila_dot
Hero Member
*****

Karma: +173/-11
Offline Offline

Posts: 1709


« Reply #9 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).
Logged
julex
Hero Member
*****

Karma: +79/-4
Offline Offline

Posts: 923


« Reply #10 on: May 20, 2013, 06:30:41 AM »

Thanks for the thresholds!
Logged
ABCD
Full Member
***

Karma: +4/-0
Offline Offline

Posts: 78



« Reply #11 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.
Logged
bomby
Jr. Member
**

Karma: +0/-0
Offline Offline

Posts: 29


« Reply #12 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
Logged
phila_dot
Hero Member
*****

Karma: +173/-11
Offline Offline

Posts: 1709


« Reply #13 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
 
Logged
Pages: [1]
  Print  
 
Jump to:  

Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Page created in 0.107 seconds with 17 queries. (Pretty URLs adds 0.009s, 0q)