Tuning for Economy can be done several ways.

[ringram]

Timing primarily, especially in closed loop.
Take her to the dyno and dial it in at the min timing required for max torque.

[wait4me]

Playing with Torque converter duty cycles and apply pressures/ apply rates will allow you to modify that some.

[oztracktuning]

More torque can be found at light throttle usually by increasing the timing in the visited cells.

[MSURacing]

Actually, what I have found on the 5.3L is that bringing it into OD and Lockup sooner helps. Also, I don't let the truck kick down until about 65% throttle. You have to remember that the most efficient an engine will run is at WOT. So, if you can achieve near WOT manifold pressure, ie around 90kPa, you will reduce your internal pumping losses of the engine.

I have also found that adding up to 15 degrees of timing at cruise helps out the fuel economy. I wish we had a eddy current chassis dyno rather than the Dynojet. This would sure help out the part throttle tuning situation.

[cmitchell17]

It seems like the stock settings for the TC lockup and 3-4 is way to early and you have to bury the throttle to get it to go.

I can see if you have less of a restriction in the engine there is less pumping losses, but since you are at a low rpm is the thorttle blade much of a restriction? Like a shock the faster you pull the more resistance there is.

Wouldnt 15 degrees of timing be a lot of timing?

[cmitchell17]

Actually now that I think about it GM seems to set it to where the TCC locks when you give it gas to go uphill. So your manifold pressure would go up.

If GM sets it like that it must be right.

[2002_z28_six_speed]

Actually, what I have found on the 5.3L is that bringing it into OD and Lockup sooner helps. Also, I don't let the truck kick down until about 65% throttle. You have to remember that the most efficient an engine will run is at WOT. So, if you can achieve near WOT manifold pressure, ie around 90kPa, you will reduce your internal pumping losses of the engine.

Doesn't that depend on the engine?

I don't understand because all my 90kPa cells are alot higher than cells in the 30-40 kPa range even if the RPM goes up alot.

For example: BEFORE 1200 RPM, ~60kPa, 3.42 gears -> 70.315243%
AFTER 2000 RPM, ~25kPa, 4.56 gears -> 56.410187%

Or my VE could be off. My gas station tickets don't seem to be though.

And I would swear that my gas milage is better some days and others it is exactly the same as before. I am not a highway racer either. 70 MPH maxium with little gunning it.

Perhaps there is a difference if you have a hp motor or torque motor. Not sure.

[cmitchell17]

Wouldnt light throttle like 15-20% be just as good under 1500rpms for manifold pressure as 25-35% for when you would have to give it more gas when in OD TCC locked?

[2002_z28_six_speed]

Right now I am still doing some research but what I believed before is now rocked. I made a bunch of changes to my car and I picked up alot [ok a couple] of miles per gallon.

I don't really want to post much but I changed to a more radical gear ratio, headers, exhaust, went to OL only, removed the maf, removed a bunch of weight, put more air in the tires, taped off the grill, msd coils, and some other slight modes. I went from 27 MPG to 31 MPG on the highway with the AC on.

I am just trying to figure it all out right now. :-S

I believe that I was pulling more load with the 3.42s thant he 4.56s. But, you are taking in more fuel even though the VE table is lower because of the faster engine speed. I want to do some quick math to figure out the grams/second of fuel consumed before and after the mods and figure out the difference in fuel used.

[ForcedTQ]

Actually now that I think about it GM seems to set it to where the TCC locks when you give it gas to go uphill. So your manifold pressure would go up.

If GM sets it like that it must be right.

Thinking about this again, GM probably has the TC set to lock up when you give it gas to go up a hill (cruising in 4th or 3rd perhaps) in order to reduce the amount of heat build-up in the transmission. On the other hand, it the TC was allowed to unlock, the resultant change in RPM would allow the engine to transfer more torque to the drive-shaft possibly reducing the need for a transmission down-shift in some cases. Heat build up would be the primary concern here I believe.