Hondata

I may be wrong here, but I thought that the L. Trim value was applied all the time regardless of whether the ECU is in open loop or closed loop, right? If so, then should there not be a way to have FlashPro Manager include the L Trim value in the Lambda overlay? When I toggle this option, I only see the lambda overlay alter the lower load columns.

No, the long term fuel trim is only used in closed loop.

Hondata wrote:No, the long term fuel trim is only used in closed loop.

Wow. Why wouldn't it be used in open loop? If LTFT is +10% due to the car continuously having large STFT's at part throttle, why wouldn't it be necessary to apply that 10% all the time, even at full throttle? Basically, it seems dangerous for the ECU to not apply LTFT at full throttle ...

Because LTFT and STFT are closed loop control parameters and don't function in open loop.

Let me put this scenario forward... even with the most perfect part throttle tune, you'll still get some STFT variance, and eventually adaptive logic applies a LTFT. Say my open loop (WOT) is also tuned, to say 12.8:1 a/f. Why would I want the adaptive logic (LTFT of say, 5%) being applied to my open loop fueling? That would put me at the low 12 a/f ratio in open loop.

Open loop is meant to run free of any ECU interference, and I wouldn't have it any other way. I have my car tuned to do "X" when I floor it, and I do not want the ECU to mess with it. My advice is to address the tune if you're seeing large amounts of adaptive correction being applied.

Gernby wrote:Wow. Why wouldn't it be used in open loop?

The same reason as to why the ECU does not run closed loop under load - so that a o2 sensor failure will not damage the engine.

O2 sensor failure seems like the only point that has made any sense to me.

It seems to me that there should be SOMETHING that the ECU will do to protect the engine from clogging fuel injectors. If you have a car with 150K miles on it, and are a "regular joe" that keeps it totally stock, and just does typical maintenance, then your fuel injectors might not flow as well as when they were new. Assuming your O2 sensor is okay, the ECU will compensate for the clogged injectors at part throttle, but why not at full throttle? I understand that it won't monitor O2 at full throttle, but why not go ahead and apply the LTFT just to protect the engine?

My brother's totally stock, low mileage '06 F22C runs very lean at full throttle (14+:1), so will it just detonate to deatth at full throttle as the injectors slowly clog?

Gernby wrote:O2 sensor failure seems like the only point that has made any sense to me.
but why not go ahead and apply the LTFT just to protect the engine?

This, I hadn't even thought about O2 sensor failure.

Hondata wrote: The same reason as to why the ECU does not run closed loop under load - so that a o2 sensor failure will not damage the engine.

What if the LTFT is -20% because the sensor reading is skewed? You want that applied at WOT?

Gernby wrote: My brother's totally stock, low mileage '06 F22C runs very lean at full throttle (14+:1), so will it just detonate to deatth at full throttle as the injectors slowly clog?

He needs to address the mechanical problem and not rely on the ECU to babysit him? :D

As I said, O2 sensor failure is not something I have considered until Hondata mentioned it. In the the case of O2 sensor failure, I would NOT want an LTFT of -20% to be applied. However, in EVERY other case I can think of, I would want LTFT applied in open loop.

The issue with my brother's car is not really an issue with HIS car. My low mileage '08 does the same thing. Both of our S2000's run in the low 14's at WOT with the stock tune.

On a stock tune and 100% stock car? I find that hard to believe...

I still can't think of any reason to apply fuel trims in open loop.

The stock tune is for the stock car, if you modified it by changing various parts and are then seeing 14's a/f... that's why we have a tuning solution.

If you have a 100% stock car in good working condition, then it seems that LTFT would be just as beneficial at full throtlte as it is in part throttlle. From what I've seen LTFT on a healthy stock car is mostly about making smallish adjustments for humidity or minor differences in the engine due to things like vlave adjustment or manufacturing tolerances.

I guess the fact that LTFT is not applied in open loop explains why my AFR values vary from day to day.

I guess it would just be dangerous to go WOT in an older stock car.