how much does weather effect readings?

[CANUCKPREDATOR]

I haven't had a chance to do any logging on my truck and now that I do have some time, its gotten REALLY cold. Just wondering how air temp and humidity effect the readings you'll get from your engine?

[Sc00teR2009]

It does but the ECM still has some control to fine tune the parameters. You can tune it to get it close and hook the DS up and monitor it any time you want. Drive a few days and make minor adjustments.

[Torrid]

That's the best way to do it. It was raining the first day I started adjusting my injector slope and I monitored it and adjusted it over the next 3-4 days just on my to and from drives to work, that way you're getting multiple situations to assure you're making power safely. With the IAT timing adjustments (AKA heatsoak), the timing doesn't start pulling until around 80-90 degrees, so as long as your IAT is reading below this as you do your adjustments and you aren't getting knock retard, youshould be fine. I had my timing too advanced for my fuel settings at first and heatsoak was pulling timing to safe limits, which ikept throwing me off until I understood the IAT timing tables.

[Grumpy_Aero_Guy]

weather can effect a LOT....

your control is trying to deliver an air-fuel ratio of about 14.7 normally (unless you're at WOT --- where it wants to be around 12.6 --- not a GM thing but a physincs thing)

If the air is more dense (more mass per unit volume), then it will add more fuel accordingly.

Trims are a (second order) function of ambient conditions as well.

Humidity is more complicated. The mass of water vapor per unit mass of air will amount ot more mass per unit volume of air, thus more mass flow through the engine than on a dry day.

So, yes, weather effects stuff..

[08_Z71]

If the air is more dense (more mass per unit volume), then it will add more fuel accordingly.
Trims are a (second order) function of ambient conditions as well.
Humidity is more complicated. The mass of water vapor per unit mass of air will amount ot more mass per unit volume of air, thus more mass flow through the engine than on a dry day.
So, yes, weather effects stuff..

Exactly!
Weather conditions have a considerable effect on power output of an internal combustion engine. High temperatures, low barometric pressures and high humidity all combine to reduce engine power. The horsepower, that any engine makes largely depends upon the density of the air that it consumes and, in turn, this density is dependent upon the temperature of the air, its barometric pressure and water vapor (or humidity) content.