Tuning for Economy can be done several ways.

[wait4me]

One way is to increase the Efficency of the engine via timing or removing Slop from the trans.


The trans Slop is the easiest to fix. Remember though, the more line pressure you run, the more loss you have due to the trans pump being harder to turn.

Shifting patterns play a big role in the way the vehicle uses fuel. Think of this, When a car goes up a hill, and you see yourself having to press the TPS to 50% or more and the car just boggs down and you keep pressing it in more, Would it have been better for you to just allow a lower TPS vs Downshifting pattern? So as you go up the hill it just either unlocks the converter or performs a downshift to the previous gear. Now the vehicle will climb the hill with ease. You will see that the injector pulse width "Fuel used" will be much less as you climbed the big hill.

Another route is to use the Custom os3. :)

[ringram]

And get a real trans.. a manual T56 :D

[neil]

Is it possible post an example Jesse?
That would be great for us newcomers.

Regards,

Neil.

[ringram]

Joecar did an excellent autotrans tutorial.
If you do a search you should find the thread.
I think the thread has a pdf attached to it too.

[wait4me]

Another Secret is to monitor and set up the o2 switching tables to be more fine tuned and tighter. BUT!!!! you have to have the ve and maf tables perfect before you do that.

The reasoning on that is with the switching from rich to lean, rich to lean to get a "Averaged" stoch wastes fuel if it is on the richer side of things and doesnt spend as much time on the lean side.

[Rhino79]

I tuned an 05 Tahoe last week, and I really spent some time on the timing table in the cruise areas and he drove about 300 miles on his trip home and back, he called and told me that his MPG average went up about 2-3MPG!

[turbo lcc]

Will DFCO help fuel economy?

[Rhino79]

Yes from what I've read, but honestly I haven't tried to really mess with it.

[oztracktuning]

DFCO and light throttle torque tuning - making a big difference to economy.

[kbracing96]

What kind of things can you do to maximize light throttle torque?

[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.

[cmitchell17]

Yeah I never thought of that. I don't know a lot about trans but does going up a hill without the tc locked really build a lot of heat compared to accelerating normaling from a stop?

When its lock in OD the rpms are lower if it would unlock or downshift rpms would probably be about 500-800rpms more or something. This means the fuel injectors are injecting about 50-70%more of the time using more fuel. So if your engine can make more torque in lower rpms and not have to downshift it is more efficient?(the question mark is becuase im not stating this)


Since were talking about this when the tc is locked in overdrive why dosent it have some sord of overrun clutch or does it? So coasting down a hill the engine dosent hold it back?

And if DFCO helps so much I don't see any reason besides drivability why GM wouldnt have at least some. I hate the fealing that the engine is always trying to fight the brakes and goes 20 mph when ideling. Im guessing the benifit of milage isnt worth the driveabilty issues with DFCO, but then couldnt they have integrated it into the brakes? Ive heard the HD 6L90s trucks have a engine braking shifting(I guess theres no way to make a system like this on the older LS1 pcms?)