Hondata

Engine: B18C Spec R
S300 (P28)
Smanager V1.4.8
WB: PLX SM-AFR WB inputs to D14 (Gauge AFR values matches with S300 AFR values)
Part throttle tuning done at Closed Loop with S.Trim adjustment set to 0%
And ECU reset done prior to tuning.
Engine is warmed up to 81C (178F) before commencement of tuning.
Average ambient temp: 32C (90F)
The problem:
I was able to tune the engine at part throttle to AFR 14.7 and the values were pretty stable throughout.

However, after I shut down the engine for about 5 hours and went for a drive, the AFR was lean (15.5 - 16.5) until the engine reaches 81C (178F).

I would understand that if the values reflected rich before the ECT reaches 81C (178F). Need advise on why are the readings lean prior to the engine warm up to 81C.

Thanx

check your ECT compensation tables and adjust as needed. You will need to see what the ECT compensations are while datalogging.

Spunkster, thanx for the advice.
I did a datalog and found out the cause of the problem.

It is due to the IAT compensation.
During the tune, the IATc was 0% as the IAT was about 47C (117F).
After I stop the car, the IAT reading went up over 50C (122F) and the IATc was at about -1% which cause the engine to run leaner.

I guess the hot intake manifold actually heats up the IAT sensor. Therefore I will be looking for a solution to reduce the heat transfer from the manifold to the sensor to get a more accurate reading.

Will_B18C wrote:Spunkster, thanx for the advice.
I did a datalog and found out the cause of the problem.

It is due to the IAT compensation.
During the tune, the IATc was 0% as the IAT was about 47C (117F).
After I stop the car, the IAT reading went up over 50C (122F) and the IATc was at about -1% which cause the engine to run leaner.

I guess the hot intake manifold actually heats up the IAT sensor. Therefore I will be looking for a solution to reduce the heat transfer from the manifold to the sensor to get a more accurate reading.

Just a update. Further datalogging and observation leads me to the actual issue causing the leaning out. It is actually the IAT Ignition Compensation, when the temperature goes up, the timing was retard. This resulted in the leaning of the engine.

Problem solved by reducing the retard.