2005 Trailblazer

[winter200]

I have a 05 trailblazer with the inline 6. My parents have a 02 which gets a lot better mpg than mine. Mine has the 3.42 rear end and theirs has the 3.73 rear end. I figured that the 3.42 would be better for mpg but has turned out different. The problem I have noticed is that it wants to drop out of OD all the time, even with a light head wind and rolling down the interstate. I was looking in the tune file and noticed that a guy can change settings on the tranny but what ideas do you guys have to help out the mpgs and hold od? Is it even worth burning one of my vin tags on?

[ScarabEpic22]

Are you asking whether a VIN license is worth it on a TB? Man, you need to license that thing NOW and play around with the trans settings to get rid of the 1-2 slop and pull the Torque Management out. Tweak the spark and VE tables, and you have a mild tune ready to roll. Believe me, you wont know you are driving the same truck.

[winter200]

I guess I i really don't want to try to burn the tires on this one. I have my dmax for that I am mostly trying to figure out how to get some better mpg's out of it and hold OD better. I have no idea where to start on this rig, I have spent all my time on the diesel power. The wife drives the tb. What is the DFCO on tune file for? You mentioned a few things but if you had something I could look at compared to my stock that would help me get started. Thanks for the help.

[ScarabEpic22]

You dont have to man, in fact the only way I can do it is by powerbraking or it being wet out (both of which I could do stock anyway).

DFCO for the I6 is worthless, Ive played with it a little and nothing has come of it. I reset it back to the stock values my 02 came with. Focus on the camshaft profiles, thats where the power can be made. Also, play with removing say 50-90% of the Trans Torque Reduction, and then reduce the Engine Spark Retard about the same. Have to play with it till you find a spot where you like it. 0 out the shift times and then for OD holding power adjust the TCC settings. Maybe change the TPS value needed to come out of lockup and move the lockup/disengage MPH values farther apart.

[dfe1]

DFCO for the I6 is worthless, Ive played with it a little and nothing has come of it.

???????

I played with DFCO on my 2002 and it definitely helps fuel economy. I did notice that the DFCO settings don't work the way the descriptions say they do. The settings that actually work don't make sense in the context of those descriptions.

[ScarabEpic22]

???????

I played with DFCO on my 2002 and it definitely helps fuel economy. I did notice that the DFCO settings don't work the way the descriptions say they do. The settings that actually work don't make sense in the context of those descriptions.

OK then, I take it back.

What have you done to tweak it? I tried upping the upper cutoff and enlarging the window in which DFCO can activate (MPH), and nothing. Can you send me what you did, or post it? My mileage blows right now, I get 13.5-14mpg around town but still get ~20-22mpg on the hwy at ~75.

[dfe1]

OK then, I take it back.

Boy are you easy. One little disagreement and you cave in.
Take a look at the two attached jpgs. One shows the DFCO parameters I'm using, the other is logged data showing the system entering and exiting DFCO. Try these settings and see if they work for you. For reference, I have a 2002 extended LT with 3.73 gears. I get 15-16 mixed city/highway and 20-21 highway. I've also cleaned up the shift setings and added some spark timing.

[ScarabEpic22]

Well for this I can bend, I have a lead foot and complain about mileage, so every little bit helps. Im taking a long road trip today, and I will reflash these parameters in for the first part and see what my mileage does.

BTW, Im a SWB with GT4+G80 (3.73s+locker). I get about the same as you do on the hwy, but around town I get ~13.5-14mpg. I like to let the I6 rev a little in 1st before I let it shift into 2, think ~4K rpm every time.

[blandmiller]

dfe1, I have some questions about the logged data. The cursor appears to be positioned at the entrance to DFCO (as seen by the 0.00 INJPW value), but the AFR_LM11 is still showing 16.4:1? My WB (LM/LC I don't remember) goes to 20:1 during DFCO.

What settings changes have you made that don't work as described in the software? I don't think I have found them yet. I believe that all of my changes are behaving as desired. I actually don't know if I ever read the actual descriptions. I looked at the values, made assumptions about the controlling method, changed values, and logged to verify.

[dfe1]

If you notice, the Wide band value doesn't change at all-- it wasn't connected during this logging session. As for the descriptions, the MAP enable/disable descriptions don't make sense. The Enable description says "MAP must be above this to enable DFCO". I have it set at 70, which corresponds to fairly heavy throttle opening. I'm guessing the description should say manifold vacuum, not pressure, because if you notice, logged MAP is 33 when DFCO becomes active-- 103-70=33. The disable description and actual differences are similar. In the LSx systems, DFCO settings are in actual MAP values.