Help! More MPG from tune?

[waynehartwig]

I'm tuning a friends rig trying to get him more MPG's and I'm running into a wall. Best I've been able to do is ~14 mpg.

Specs:
Stock 2006 5.3, NV4500 (5 spd trans), etc.

This last time I tried setting up lean cruise and doing a MAF only, but still


Thanks in advance!!!

[TXZ0603]

scans? config? mods?

[mecanicman]

Lean cruise is disabled even though the tables are there. Modifying them does nothing. Going to MAF only tune will do nothing for you if you have not tuned the MAF table which appears stock. Also, Im confused, you said it was a 5 speed but program is for a 4L60?

[waynehartwig]

scans? config? mods?

What do you mean?
There is no mods on the motor, well maybe a home made cold air intake.
I have no scan logs - would it help if I did? And if so, what are you looking to see?

Lean cruise is disabled even though the tables are there. Modifying them does nothing. Going to MAF only tune will do nothing for you if you have not tuned the MAF table which appears stock. Also, Im confused, you said it was a 5 speed but program is for a 4L60?

That makes sense on the lean cruise - dang! I spent some pretty good time setting it all up without any real knowledge of it.

I tried the MAF only just to see if it would make a difference and it didn't.

There was never a 5.3 from GM with a manual trans. The PCM and engine came out of a rig with a 4L60E. If you look through the tune, you'll notice I turned on things like shift light, and etc. Is there more that I should do?

A big name company tuned this before I got to it. He had lots of drivability issues as well and low MPG complaints. I basically just put the tune back to stock and make some changes. Fixed all of the driveability issues, gave him notiecably more power, but not any increase in fuel economy - which is really what he wants. He lives about 250 miles round trip from me and is driving up a third time this weekend so I can see if I can make any other improvements. Now he has even larger tires and he says his fuel economy is now 11 mpg and wants me to put the original modified tune back in with some of my current mods to fix the driveability issues. IMO he's going backwards and will do everything I can to talk him out of going back to the original tuen that he was having issues with.

I believe all of his MPG accounts are calculated numbers on a scan tool, and not actual at the pump numbers. I also believe that since he just installed larger tires that the MPG calculation is onw off because the PCM doesn't know he has bigger tires? So the first thing I'll do is tell the PCM what he has and see if the calculated number goes back up.

...When he left this last time, I was seeing low 18's on that scan tool thingie he has. So I'm not sure what's going on......

[mecanicman]

Depending on how its wired, the pcm may not know the difference between park/neutral and in gear. I would look for a compatible 6.0l with 5 speed tune and flash it in or ask support to do a segment swap. If you find a compatible 6.0 tune just change the displacement to 5.3 and you should be good.

[waynehartwig]

Depending on how its wired, the pcm may not know the difference between park/neutral and in gear. I would look for a compatible 6.0l with 5 speed tune and flash it in or ask support to do a segment swap. If you find a compatible 6.0 tune just change the displacement to 5.3 and you should be good.

Why would that matter? If you really think it's an issue, I'll suggest it to him.

In the beginning one of the issues he had was shifting gears, the RPM's would go up to about 2k everytime he put the clutch in. I fixed that easily by activating some of the shift things, getting rid of the PRN selection, etc. and now it behaves like it should.

But now it runs/drives great, he's just not happy with the MPG's he's getting.

[mecanicman]

If I understand correctly, and im sure someone will correct me if im wrong, when it thinks its in park/neutral it runs off the idle parameters. Im not sure it ever sees your spark timing tables, its running off idle table. A segment swap or new 6.0/5speed operating system is probably your best bet as well as making sure the pcm sees the correct inputs for a standard transmission.

A log file would help to see this.

[waynehartwig]

If I understand correctly, and im sure someone will correct me if im wrong, when it thinks its in park/neutral it runs off the idle parameters. Im not sure it ever sees your spark timing tables, its running off idle table. A segment swap or new 6.0/5speed operating system is probably your best bet as well as making sure the pcm sees the correct inputs for a standard transmission.

A log file would help to see this.

Hmmmm I'm about 99% sure it's seeing my timing tables. I've logged drive times with it, but I never saved them, because I just didn't think it was necessary. One of the reasons I was logging, was so I could watch the commanded AFR's.

But I'll log it up this weekend. What should I log? And if you could make me a log dealy that would be even better Because I've never figured out how to add custom PID's.

[69lt1bird]

Your narrow band O2 sensors are still going to try to get you back to stoich no matter what you do. If you are using a wideband and you have the AFR correct under all driving conditions there is probably not a lot you are going to be able to do with it. Without DOD/AFM to deactivate the cylinders a truck is a truck. My 2001 5.3L 4x4 extended cab auto with 3.73 gears, gets 14-15 mpg mixed driving and on the highway.

Is he actually checking the gas mileage by filling the tank and then calculating the miles driven or is he going off the instant/avg mileage gauge in the truck?

[WS6FirebirdTA00]

How do you expect to improve gas mileage without logging?

The only thing you can do is dial in the fueling tables, make sure the switch, points are setup correctly, setup the timing correctly, and tell your friend to change his driving style (as that will net the most gains).

Most trucks I do see between 1-3 MPG increase depending on year, size, mods, etc.

[waynehartwig]

Your narrow band O2 sensors are still going to try to get you back to stoich no matter what you do. If you are using a wideband and you have the AFR correct under all driving conditions there is probably not a lot you are going to be able to do with it. Without DOD/AFM to deactivate the cylinders a truck is a truck. My 2001 5.3L 4x4 extended cab auto with 3.73 gears, gets 14-15 mpg mixed driving and on the highway.

Is he actually checking the gas mileage by filling the tank and then calculating the miles driven or is he going off the instant/avg mileage gauge in the truck?

How do you expect to improve gas mileage without logging?

The only thing you can do is dial in the fueling tables, make sure the switch, points are setup correctly, setup the timing correctly, and tell your friend to change his driving style (as that will net the most gains).

Most trucks I do see between 1-3 MPG increase depending on year, size, mods, etc.

I agree with both of you, it's a truck. But he thinks he should be getting more than 14 mpg with easy driving. I'm not sure what else to do, that's why I put this up here, to see if any of you had any thoughts on my tune. Maybe there is something I'm doing/not doing that stands out in the tune.

I believe he's also checking it at the pump - or at least he had better be. Futile if not.

I logged the tune, but I never saved it. Logged, viewed, deleted. This weekend I will log and save it.

He doesn't have a WB, so I haven't done any MAF/VE tuning. His ST/LT trims aren't bad. I don't recall seeing either above +- 6% at anytime.

[WS6FirebirdTA00]

Fuel trims don't matter if they are trying to switch around the wrong point. That is why you should verify with a WB as that is probably your best shot as saving gas.

[waynehartwig]

Fuel trims don't matter if they are trying to switch around the wrong point. That is why you should verify with a WB as that is probably your best shot as saving gas.

What would cause them to switch around the wrong point?

[WS6FirebirdTA00]

The wrong switch point in the tune.

[waynehartwig]

The wrong switch point in the tune.

Ok, well you see the tune, is set wrong?

[WS6FirebirdTA00]

Can't tell without having a WB in place to see where it is switching around.

[jimmypop13]

I know there was an idea to find how much air you are using when cruising around 65-70mph and adjust the switch points that correlate with that amount of airflow down to a lower value. Lowering the switch point value can cause you to go a little lean. I'm using bosch o2s and this works well because they are so slow. I had to raise the switch points quite a bit from the stock values just to get my car to run around 14.7 because it was running so lean with the stock switching values.
I've had LTFT's disabled and STFT's couldn't correct the lean condition from the slow Bosch o2's so I don't think LTFT's could either.
I'm not sure if it would work so as well with the stock a/c delco o2's though

[waynehartwig]

I've got a WB, but it's installed in my rig.....I guess if I plan on fixing this, it's time to put a WB in and see what's really going on.

[WS6FirebirdTA00]

LTFTs are learned from STFTs. If the short terms aren't doing anything to correct back right, there is no reason to expect the LTFTs to.

[jayss10]

Does anyone have a tune for mpg ,to run in my, 2000 Silverado 2500 automatic lq4, power isn't as important as mpg I have to drive 50 miles to work ,HELP ...I get 12-14 mpg