Hondata S300 and IAT compensation (IGN)

The previous article I mentioned that the Fuel Compensation for IAT was affecting my AFR readings.  After more datalogging and observations, I found that the bigger culprit was the Ignition Compensation for IAT.  Essentially it was retarding the ignition once the IAT sensor reads 51C and above, resulting in the leaning of the engine.  The leaning did not reoccur once I made adjustments to the compensation values.

However, the best way is still to relocate the IAT sensor to the air intake pipings like in the EKs instead of the intake manifold.

Hondata S300 and IAT compensation

More to share on tuning using S300.  

Background: I was tuning my car for part throttle (cruising) and managed to have a stable 14.7 AFR reading through column 1 to 5.  However after I shut down the engine for a while (couple of hours) and drove again,  I got lean readings (greater than 14.7).  I was expecting richer AFR than 14.7 rather leaner reading as the engine has cooled down.

I did a datalog and realised that the IAT readings were quite high which caused the ECU to reduce the duty cycle, resulting in a leaner AFR reading.  This might be the IAT sensor being heated up by the hot intake manifold.

2 lessons learnt:

1) When tuning your engine, try to make sure the IAT and ECT values are the same for each run as it affects the AFR value greatly.

2)   If possible, try to find a way to insulate the IAT sensor or minimise heat transfer from the Intake Manifold to get a more accurate reading.

Once u manage to tune your engine as desired (with constant ECT and IAT values),  you can adjust the fuel compensation for IAT and ECT accordingly since the default value may not be the ideal compensation required.

Hondata S300 closed loop operations

Since I had the S300 installed and tuned for more than one month ago, I have been trying to fine tune the fuel.  The main problem that I had was to enable closed loop operation after I have complete my open loop tuning.  The AFR runs really lean (17.0) after I enable the closed loop operation even though AFR reading during open loop operations were fine.

After going through the Hondata forum, I found some solution.

1) As the car was usually driven in closed loop operations, the ECU would have Long Term fuel trim inputs which will affect the duty cycle. The solution is to reset the ECU before tuning.

2) The symptoms above which I describe apparently affects only some ECU, the work around is to set the short term fuel trim settings under the closed loop tab to 0 for both maximum and minimum short term adjustments and tune the car in closed loop operation instead of open loop operations.  (remember set the values back to the original after completion of tuning)

3) Next is to adjust the Rate of change to the recommend setting by hondata as below:

This will minimise AFR fluctuations, thus improving drivability and milage.  The settings that I used was 5 for all slow value and 99 for all Fast value. 

Plse note: The tuning done on my car was based on the PLX wideband AFR.  Plse do not attempt to tune the car without at least wideband AFR, however u may try altering the rate of change even without a wideband AFR.

Definitions:
Short term fuel trim is the amount of fuel adjustment made by the ECU depending on the AFR reading

Long term fuel trim is the amount of fuel adjustment made by the ECU based on the average Short Term fuel trim made over a period of time

Rate of Change is the rate of change of fuel trim made by the ECU.