[Longshot270]

Good post Skip
But I want to add to a few of your points.

Originally Posted by Skip_1074

You never experienced a lean code with a CAI and the Edge because even though the Edge wasn't calibrated specifically for the CAI that you were using, it had altered your fuel trim already thus providing more fuel to the engine. That being the said, without actually knowing the strategies, or understanding them for that matter, that Edge uses (and many other factors such as tune used, octane used, CAI brand and tube diameter at MAF sensor in comparison to stock), I believe that your the Edge kept your A/F ratio with CAI somewhere around the what the stock programming had.

That is a good observation. One thing that is recommended for people with CAIs are the canned tow tunes. They are written with a richer A/F ratio and it helps counter act the lean effects.

But you also have to remember every truck runs a bit different so there is a bit of luck involved. He was lucky and no codes came up.

Originally Posted by Skip_1074

If you have a two hoses and pretend that the small one is stock and the larger is a CAI...lets say a 3" (7.07 square inch cross section) and 4" (12.57 square inch cross section)...and a sensor that is 1" by 1" (1 square inch) that extends into them. The sensor is designed to take a sample from 14.14% of the 3" hose and that is needed to provided accurate flow calculations, but when placed in the 4" hose, it only takes a sample from 7.95%. That means only 56.22% of the required sample is being provided for the calculations.

I bolded the part that I usually find important. Air is a fluid and fluid dynamics is a tricky subject. A more important comparison would be the velocity of a specific amount of air through different sized pipes. The engine is nothing more than an air pump so the air flow that is entering can be calculated mathematically. With the narrow pipe the sensor might read 65 grams/sec but with a larger pipe it might only read 55 grams/sec. That difference is what causes the lean condition because the truck fuels for 55 g/s instead of 65 g/s.

Here is where the O2 sensor comes in. Their purpose is to make sure the truck is running around stoic for emissions purposes. The O2 sensor will attempt to correct the issue but it does not have nearly as much influence when the MAF sensor is still operating within the predetermined parameters of "working sensor". When these two sensors do not agree enough you have rich and lean codes. But there are many other sensors that contribute to the codes.

Originally Posted by Skip_1074

Okay, on the the exhaust and addition to an Edge and CAI. "A chain is only as strong as it's weakest link." This works two ways on an engine:

1. You can only suck in as much air as the exhaust system can expel.
2. You can only expel as much air as the intake can suck in.

My understanding is the first was the case with your truck. The addition of a free flowing exhaust freed the engine's ability to take in more air from the CAI already installed. As stated before, I believe that the Edge held your A/F ratio similar to stock, but I also believe that the tune did not provide a large enough increase in fuel for both the CAI and exhaust system you added, thus causing the lean issue.

Where I am not sure how O2 sensors play into the equation. I know that some vehicles (don't remember which ones right now) are very sensitive to changing them as well as changes in their placement. I don't know if this played any part in your situation or not, but I figured that I would toss that out there too.

I can't say for sure but this echos the same effect as the CAI to the MAF sensor if you go to a larger pipe diameter with the same O2 sensors.

Originally Posted by Skip_1074

Longshot, don't be bringing age into the equation here. We each have one goal here, to exchange information and learn from the information someone else provides that we didn't already know. But since you brought it up...I'm only 27.

Only 27? You guys crack me up. Try being 19 a month ago, being 18 when I got promoted to a jr mod. You have to realize that, regardless of it being important or not, many people think age does make a difference. Doesn't help that I look 16 and have no official mechanical experience. My dad still refuses to let me work on my truck when I'm home. I was using the age as an example why the forums are good at building intelligent discussions because you can't assume somebody doesn't know what they are saying based on appearances, as I've encountered many times in face to face discussions.

Originally Posted by Skip_1074

I've spent well over an hour typing this and I think I confused myself now, or maybe its just the fact that I have been up all night working and still have another 4+ hours to be up. If I missed anything, you have questions, or whatever, please let me know. I'm off to go play with some numbers to waste time. After I've slept, I'll try to post some interesting just for and giggles facts that I'm going to try to derive, now I've just got to find the excel files I have.

Thats ok, I spend a few hours typing that long post too because I was watching a movie.
I usually go fishing to waste time...but whatever floats your boat.