selected for reading. When we want to use OBD corrections it is recommended to leave only
Long Time Fuel Trims 1 [%] (and Long Time Fuel Trims 2 [%] in case of having 2 banks)
parameter selected for quicker update.
“Read error codes”
-reads stored error codes from the OBD with the description of each code.
“Erase error codes”
-erases stored error codes from the OBD. In some particular cases for
successful erasing of OBD error codes we need to do it when the engine is off, and +12V from the
key is being given to the controller (ACC position of the key).
Parameter
“Max. correction [%]”
shouldn't be bigger than 15%. This parameter sets the maximum
value of
Long Time Fuel Trim
which gas controller will try to adjust by changing gas injection
opening time. In example, when this parameter will be 15% and the LTFT value will be
±
25%, the
OSCAR-N OBD CAN SAS controller will be trying to adjust the injection opening time just like
for the
±
15% value.
OSCAR-N OBD CAN SAS controller reads the value of mixture correctors from OBD and sets the
amount of gas injected so the
„Short Time Fuel Trim”
(STFT) i
„Long Time Fuel Trim”
(LTFT)
will be oscillating as close to expected car's manufacturers default values (so called “
neutral
point”
) as possible. It is possible to set different neutral points for idling and higher revs conditions.
STFT and LTFT mixture correctors are referring to the corrections dynamically imported to table of
injection opening times in original petrol ECU. These corrections are being made all the time to
obtain the ideal proportions of stochiometric value of air/fuel mixture (14,7 : 1). STFT are referring
to temporary conditions of driving (like rapid accelerating, braking etc.). LTFT are referring to long
lasting conditions (like work of the engine on idle) and they are being an averaged value from
STFT.
Corrections are showed up as a percentage. Positive value means that in that particular moment the
mixture is too lean and petrol ECU is trying to elongate the petrol injectors opening time to enrich
it. Negative value means that mixture is too reach and petrol ECU is trying to shorten the injection
opening time to make it leaner.
The concept of
banks
is referring to “V” type engines. Cylinder marked as no. 1 should be always
in bank no. 1. “V” type engines should always have one side assigned to bank no. 1 (cylinders with
numbers from 1 to 3 or from 1 to 4) and another side to bank no. 2 (cylinders with numbers from 4
to 6 or from 5 to 8). Straight type engines should have all the cylinders assigned to bank no. 1.
Algorithm of controller's adaptation in dependency of OBD corrections is basing on reading actual
values of STFT and LTFT and depending on these values elongating or shortening gas injection
opening times. In result of such actions mixture is being enriched or leaned to keep the STFT and
LTFT in desired range.
In example: if LTFT are going too far in positive direction (they are growing), algorithm is
increasing the gas injection opening time to enrich the mixture, so finally the LTFT are going in
negative direction (they are falling).
If the LTFT are going to far in negative direction (they are falling), algorithm is shortening the gas
injection opening time to lean the mixture, so finally the LTFT are going in positive direction (they
are growing).
Actual value of calculated corrections we should control from time to time. To big absolute value of
these correction mean that some mechanical part might be worn out and we should make some
mechanical adjustments to some parts of sequential gas injection system.
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