Engine Braking –
Rows P1, P2, and even part of P3 can be corrupted by engine braking. When lifting the
throttle during engine braking, the ECU does not inject any fuel. The engine is
effectively an air pump and the AFR will be off the scale lean. This is normal, however
the data collected during engine braking is useless and often causes users to add and
add fuel to try to correct this.
Missfires –
When an engine miss-fires it will pump unburnt fuel and fresh air into the exhaust
system. Because the Air fuel ratio is actually measured by an oxygen sensor, this
shows up as a lean mixture due to the excess of oxygen. This will often show up on the
LM1 display as a dancing AFR reading from rich to lean. On the logging this will be
averaged out, so you won’t see it. If you have misfires in a particular area, do not use
the logged data at face value.
Erroneous Data –
While logging, blipping the throttle, rev matching shifts, or engine braking can give bad
data in various spots on the map. If there is an odd air fuel reading surrounded by
reasonable numbers there is a good chance that it could be a bad number. To help
identify these bad numbers the map watch has an option that let’s you view the number
of data points that were collected in a particular cell. In step 6 we set the logging to view
the data. If we select NUM instead of average it will display the number of data points
collected in that cell. If only 1 point was used to generate the data and the data is
strange, it’s likely a bad data point. It is still a good idea to check the injection maps to
see if there is an unreasonable dip or spike in the numbers in that cell.
Data Interpolation –
While driving, the car does not really run in any one particular cell. The car will run in
between two or more cells. The ecu uses linear interpolation to calculate the values that
the ECU should use to run the car. If you have a high value in the injection map it will
tend to add fuel to the cells around it. For this reason tuning is a lengthy iterative
process that requires several sessions of data collection and manual smoothing of the
injection maps. After running some logging sessions and making changes based on
AFR, go back to the MAP and look for strange spots in the MAP. Look for high values
surrounded by low values, or dips in the curve. The fueling should increase with Boost,
and should generally increase with RPM near the torque peak of the engine, and then
drop off slightly.
Data Processing –
With all the data in the 20 x 20 grid it is very tedious to change all of the points in the
injection map. It is best to use a spreadsheet to process the data automatically, and
then paste the changes into the injection correction map. Using a spreadsheet to
process the data can often get the air fuel ratio within 5% in just a few logging sessions.
こんな感じです。。。（￣□￣；）えっ！！
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