Imo without changing parts the only real achieveable way to increase mpg is to adjust the timing at cruise. What you shot for at cruise is the highest intake vacuum (meaning more negative). This assume that the airflow tables are tuned correctly which should be the foundation of any solid tune. Timing=power.

There are a couple of other tricks, such as lower O2 switch points then adjusting the airflow tables to realign the trims.

 

Other tricks are adjusting the burst Timing tables to not pull timing at throttle transitions.

Adjusting hour transient fueling tables to not add as much gas upon throttle increase. And doing the opposite on throttle close.

More agressive dfco

Lowering you throttle cracker in the upper mph range so it is not feeding unneeded air making the throttle hang creating the cruise control affect. This has a positive affect on dfco.

Those are just a few i could think of off the top of my head.

 

Also keeping your ve and maf tables SMOOTH helps, rocky mountain tables cause unstable/unpredictable fuel trims.

 

You need to get the most bang for your buck. The most power out of the fuel.

Adding EGR so you can add timing is defeating adding more timing.

If you were at a cruise all the time then you are correct with the timing.

Remove the EGR, Add timing, Change shift tables, Lockup and unlock the converter differently, PE mode -- Sooner in the sooner out and the more MPG, don't lean the car out because it will save you penny's compared to other ways.

If you lower the amount of airflow you increase MPG, but you need to look at it over the complete trip. I think I have a report some place that stated X amount of the fuel was used at startup -- Y amount was used at Cruise, and Z amount was used at stops and acceleration. Z was the most used hands down. If you get some from cruise great and that is the easiest to do. You will save money and gas, but if you work on the stop and getting up to speed you can save even more.

 

I don't tune my truck but I like reading tris kind of stuff, even if my head hurta a little lol.

On a side note and since you mentioned idle speed, I don't like how on fuel injected vehicles when you give it some gas in neutral the idle speed hangs up in the rpms.

Is it possible to make it act like a carbed truck? If you chop the trothle idle speed comes down imediately after you take your foot out of the gas.

 

To answer your question yes. Tell justin what you just said and i am sure he can adjust your tune.

The crazy thing about GM tunes is that they have twice as many tables and adjustments for idle compared to anything else.

 

Its the tune i started with back in 2006 or so. So 15.5 for regular gas.

Im not quite sure what MBT is. But ive put over 100k miles on this tune towing, racing and highway miles. I guess it works or i should have seen a problem arise by now?

 

No you wouldn't see an issue unless it's way out

I will explain MBT/optimal timing and MBT again, but read back through this thread

 

LOL
Have you ever seen air stall out? I just don't understand why people do that to the MAF xfer

 

So that means your at 16.1 to 1 AFR?