5.3 "LMG" swap, getting a E38 started, fuel economy

[harascho]

Here are two of my first logs. As I explained in other corners of this forum I have a 1997 Tahoe with a 2007 5.3 LMG, 4L60E, E38/T42 combination.
Beside some other problems the fuel economy or lets say the nonexistent fuel economy is a thing I have to work on.

As my knowledge of tuning is still in a steep learning curve I may need some help to interpret what I recorded on the testdrives...

I took the opportunity to take my tahoe on a longer trip. I had to drive to the south of Germany. It was about 200mls, a forth of it through some small towns and country roads, the rest a longer stretch of our autobahn. I set the cruise to 70mls/h and watched the AFM working. It only kicked in when the road went downward (very little was enough to get V4 mode) .As soon as the road was flat I was back to V8 mode. Without the cruise it felt that the slightest movement of the throttle and I was back in V8 mode. I think there is room for some refinements so that the V4 mode is kept longer even with a little throttle applied.

The overall fuel consumption was 13,7mpg which is what I think very high for that very careful right foot.
what could be done to get better milage out of a e38 controlled LMG 5.3?

Is there a way to get a kind of lean cruise mode? Could I tweak the calibration to get more miles out of a gallon? Ideas to widen the V4 zone where adequate..?

To the logging of the important PID's. What should I keep an eye on when I am looking for a better mileage?? Could there be something wrong in my application ?? The only thing I see is a strange TCclutch slippage, like a sine wave (30 - 80rpm)
The fuel consumption Patrick and Vegasrobbi report are a whole different story.

best regards and thanks for your help

Harald

[GMPX]

I suppose the first step would be to figure out why AFM is disabled so easily (remember the new PID).
There is no Lean Cruise at all, that was gone since the E40 came out.

Cheers,
Ross

[gmtech16450yz]

Lower numbers in B0950 will let AFM come in easier (at a lower vac).
Lower numbers in B0951 will let it stay in 4cyl easier (takes more of a vac drop to come out of 4cyl mode).
Raising B0960 to 8 or 10 will make it less likely to come out of 4cyl mode because of tps.

Make sure you're getting as much timing advance as your fuel will take. Don't expect much, a certain size motor making a certain amount of hp moving a certain size weight at a certain speed will get a certain mpg, period. You can move the numbers up or down slightly but not much. Don't believe all these guys that say "my mileage went up 2 or 3 mpg after I put my CAI on". I've got 30 something years of logging and trying to change mileage in hundreds of vehicles and here's what I've found... it's pretty easy to increase performance, driveability and throttle response but it's very hard to effect mpg. What usually happens when tuning for better efficiency is you get more hp and torque and it doesn't LOWER your mpg. Most likely because you just end up using more of that hp.

FWIW, I've been looking at the DIC average mpg on a large percentage of the 6.2 Denali's I've been working on for the last couple of years, just to see if there's a common number on all of them. After looking at them for awhile I realized there was a pretty solid common average- 12.6mpg! Some of them had never had the average mpg reset so they show the average over 30k, 40k, even 50k miles. (you can tell by the gallons used when they reset it.) The biggest factor on that mileage is AWD, or 4WD. You're going to get at least 1, maybe 2mpg less with 4 or all wheel drive.

Sorry for the long post. My advice is keep the AFM settings stock, run prem fuel always and get your timing as high as you can. Oh and if you have a steady foot, you will get better mileage if you don't use your cruise control.

[harascho]

Don't expect much, a certain size motor making a certain amount of hp moving a certain size weight at a certain speed will get a certain mpg, period.

You are absolutly right with this. But I know my driving habits and when cruisin' with a 2001 Suburban 4wd in CA including a trip to Death Valley with the AC running I could manage to get about 16mpg. And I could repeat this several times.
So the Suburban is a whole different thing than a 2dr Tahoe.
Did you look at my tranny log? That strange sine wave of the TCCslip PID? Is that normal?
My problem is I don't know, do I log something odd or is it just quite normal. Also the timing and the fuel trims in the other log, could they be called normal?

Harald

[joecar]

Harald,

I now think that that much tcc slip is not normal (thanks to discussion with jfpilla......and review of some old logs)... since TIS:TOS matches the known gear ratios, the conclusion is that the tcc is slipping...

Also, something else that looks wrong is TCCMODE... this is showing "Slew" most of the time (instead of "Locked")... I don't know certainly, but this doesn't look right.

In addition to those pids, also log other pids like TCCDC, RPM, VSS, GEAR, TFT, ECT, IAT, MAF, MAP, TFMPRS, MFTOTAL (misfires).

Cheers
Joe

[harascho]

In addition to those pids, also log other pids like TCCDC, RPM, VSS, GEAR, TFT, ECT, IAT, MAF, MAP, TFMPRS, MFTOTAL (misfires).

I'll do my very best, but when logging T42 stuff I cannot log E38 PID's at the same time.

To the tranny , I hope to find something in the tune files 'cause the tranny and torque converter where almost new, they had 9miles on them and this proved to be true... (engine had 6miles....) So we are talking about a real new engine and tranny.

here are the pid and dash I prepared for logging tomorrow

Harald

[joecar]

Oh, yes, I forgot about not being able to log 2 modules simultaneously...

[joecar]

Those pids are sufficient.

[harascho]

I went through the T42 TCC parameters and found only the apply/release/and pressure settings.
I could not see anything about the TCC mode when it should be locked when it is in slew mode...etc.

Did I miss something or should I dig into the E38 tune?

Harald

[gmtech16450yz]

"Slew" during lockup is normal. Don't know enough about it to tell you why though.