While high humidity may help keep temps down it is indeed bad for making power. More water in the air means less oxygen and room for compression.

Humidity is not really your friend, unless you're having a day in the pool.

In reference to fuel trims, the MAF sensor is very good at compensating for air density based on temperature, but introduce big changes in humidity and it then becomes apperant the MAF has some limitations. In my experience, humidity was the single biggest contributor to varied results because of operating environment.

The PCM will apply the last used LTFT value just before entering PE mode. That means that if your LTFT value is -6.2 for example, this fuel correction value will be applied to all fueling while in PE mode. Since the LTFT is in percent, the example above would pull 6.2% of the fuel target (AFR) the entire time you're in PE (Power Enrichment) mode. I've seen many cases, even stock, where the LTFT locks at -12.5. When more than a few percent of fuel is pulled you could end up with problems. This value can and will change with weather.

As a rough rule of thumb, once your MAP value is above 100 Kpa (~atmospheric pressure), then you should be in PE mode, which means the O2 value is ignored and the fueling is aplied from predetermined values, subject to the correction factor of the LTFT.

Ideally the LTFTs would lock at 0 while in PE mode. This is possible under most weather conditions, but not all. Typically people have winter and summer tunes.

Maybe you'd want to consider investing in a PCM programmer/scanner instead. Even if you wouldn't want to make major PCM changes, there are some changes you could make to improve the effectiveness of your current PCM tuning that could never be made in advance on a bench. Since both HP Tuners and the DHP Powrtuner have built in scanners, could be a great idea for you at this point.

Cheers,

Thanks.
Learn something every day.
I won't consider dropping pulley sizes until I check it all out first.

This will probably be as far as I'm going to mod now.

It's time to concentrate on other things in life.......

Uh huh..... :roll: