How much air?
 

More air is better for a diesel? What is the best turbo air filter setup for max air?

I would think so. The stock turbo is not going to push too much air, so get as much as you can. A ot of guys here are running AFE II's, and I hear a lot of good things from them about how they like them. I have a DIY CAI, with an airraid drop in replacement filter. One of the Diesel mags did a dyno run with stock air boxes and the replacement stuff on a stock truck, and there were very little gains. I hear that the stock airbox and filter are good up till 500 hp.

Very good point.
Back to the original question. How to get more air without adding more fuel?Can the air fuel ratio be improve with more air in the stock form? I left a intake clamp loose once and man the low end power was a lot better, no trubo lag. I figured out real fast what I'd done and tightend it up. MPG gains are what I'm looking for not power or performance not that they won't go hand in hand.

I read in a diesel mag awhile back about a guy that was trying to get the best mileage he could out of is powerstroke. He basically detuned the motor and put smaller injectors in, higher gears and built some crazy aerodyamic thing in the bed. He was getting 28mpg.

Less fuel more air in air/fuel ratio?
 

Why would less fuel get better mpg maybe more air in the air fuel ratio? Or is it atomization of the fuel? Why do people get better mpg with bigger injectors and more fuel?

The bigger injectors usually have a better spray pattern and therefore better atomization. The only things I can think of to get better mpg would be a better intake, exhaust, advance the timing (rokktech, tone ring mod) and possibly a small pressure box with some Flux 1's. I'm sure if you change the cam and port the head you'd get more air, but your looking a some serious $$$. How far are you willing to go?

Better spray pattern/atomization.
 

If that's all it takes is better spray pattern then why doesn't cummins/dodge get it right to start with?
I can't see spending lots of $$$ to get better mpg. If a person were to "have to replace" the injectors what is the best options? Bigger or just better injectors?

Dodge isn't going to spend the money either. A more efficient injector = more $$$. Most companies that make aftermarket injectors make them bigger. Don M's are probably the best, but they are more expensive. He's got his Flux 1's that are rated at an additional 40hp. DDP also does a good job on theirs and they're a little cheaper.

I don't know much about injectors so please fill me in. What diffence is there between a good spray pattern and a bad one? If that is the only real difference?

Other than volume, yeah. Imagine taking a spray bottle and filling it with gasoline. (Don't attempt this please!) Put it on fine mist and spray and light. You'll get a big flash because the gas is mixed very well with the air. If you were to put it on straight stream you would just get a stream of flaming gasoline. That's basically fuel atomization in a nut shell. The better the spray pattern the better the burn. We have to test the fuel nozzles on C-130s for spray pattern every 180 days so we can make sure we get an efficient, equal burn. If it was off you would get low power and possibly burn up the turbine.

I've used diesel in a spray bottle to help get a fire going. The finer the spray the quicker and better it burns.

Why isn't someone simply doing a spray pattern mode to increase the efficiency of a stock injector?

Probably because it would take the same amount of money, and for the price you might as well get more power as well. The larger injectors, if driven nicely, will usually not drop your fuel economy.

I read in a Diesel Power Mag about the CP3 and how the triangular hole is made smaller on purpose to allow for just such better spray pattern and atomization.( Able to do this because of H.Pressures of Comm. Rail. A Lot of guys are doing a homemade CP3 mod by making the hole bigger to get more fuel. I wonder if their mpg will go way down? They say they get more power, probably do since more fuel? be interesting to see a dyno of before and after this mod.

Alot of guys are claim better mileage with pressure box and advancing the timing. I guess (thinking of the spray bottle comparison) the harder you squeeze the finer the spray.

The CP3 mod is not the injector. It's the pump. We've got away from "How much air"? How well the fuel burns in the air is a big factor. Is more air really going to make any difference. Didn't the nonturbo diesels get good mpg but had no power?