[RDF1]

Posted a reply to this in the comments- forgot to hit reply lol

Short term bank 1 looks like it has an exhaust leak or misfire. Bank 2 looks much better.

 

[3dhawkeye]

I hope I'm wrong, but this may be a tough one to pin down Hopefully someone here can point you in the right direction. Let us know what you come up with.

 

[JamalTheSilverado1965]

Short term bank 1 looks like it has an exhaust leak or misfire. Bank 2 looks much better.

No live misfires according to scanner at any point. I suppose there could be a small exhaust leak I havent found..?
It audibly sounds normal, would that small of a leak throw MPG that bad?

 

[RDF1]

No live misfires according to scanner at any point. I suppose there could be a small exhaust leak I havent found..?
It audibly sounds normal, would that small of a leak throw MPG that bad?

No but it was just something that stuck out to me.
Some tuners disable Long term fuel trims cause it can skew with their PE/WOT fueling. But its just a poor excuse as to not dialing in all the fueling.

 

[06MonteSS]

Yeah, he's had it tuned before already by someone else using hptuners tuning software... You'd need to get the truck ECM & TCM modules flashed back to the factory stock GM programming, then you could use a diablosport programmer on it and get a custom tune done...

Doesn't sound like that guy did a full tune really... Did he do driving data logs, and adjust your airflow/fueling by rescaling the MAF sensor for how the truck is running??

What are your average long term fuel trims for bank 1 and bank 2 ???

etc. etc... could be different things...

BUT - Make sure you are using GOOD gas, it makes a difference... Mobil, Exxon, Sunoco, Amoco, BP, Chevron - are the best brands to use...

NEVER use Shell, walmart/sams club/bj's, mom-n-pop, or no-name brands, as it's crap gas/additives that tends to cause a lot of knock retard and less performance/mpg...

Once people switch, they usually notice better mpg, better response/performance, etc...

Also, a lot of people tend to get better mileage with higher 91-93 octane gas...

 

[Bubbanbrenda1]

Thats all I run.
I reached out to him asking if he kept my logs and can send them over.
I emailed a bunch of other guys who wouldnt help because they thing MPG is a mechanical issue and said there's nothing they can do.

Ask him to email the current tune file and and a steady state log file.

 

[EdgecrusherXES]

Looking at the totality of this thread few things stand out.

The wheels and tires are going to impact your mileage plus the lift that is 1-2 gone right there. More air under means more drag and the increase unsprung rotational mass is going to have the biggest effect especially the tires.
The tune is definitely going to have an effect.

A lot of what Lew mentions could be your issue... What E10 are you using 87, 89, 91 or 93? What is the tune setup for?

See if you can get some ethanol free fuel and see if it has any change. The removal of ethanol should see a boost in fuel economy also.

 

[JamalTheSilverado1965]

Ive gone through all the fuel companies in every octane for testing purposes. Ran them all consistently for a month and nothing has ever changed. LTFT are disabled completely. He told me he did a full street tune on it. I did ask for data logs

 

[JamalTheSilverado1965]

Yeah, he's had it tuned before already by someone else using hptuners tuning software... You'd need to get the truck ECM & TCM modules flashed back to the factory stock GM programming, then you could use a diablosport programmer on it and get a custom tune done...

Doesn't sound like that guy did a full tune really... Did he do driving data logs, and adjust your airflow/fueling by rescaling the MAF sensor for how the truck is running??

What are your average long term fuel trims for bank 1 and bank 2 ???

etc. etc... could be different things...

BUT - Make sure you are using GOOD gas, it makes a difference... Mobil, Exxon, Sunoco, Amoco, BP, Chevron - are the best brands to use...

NEVER use Shell, walmart/sams club/bj's, mom-n-pop, or no-name brands, as it's crap gas/additives that tends to cause a lot of knock retard and less performance/mpg...

Once people switch, they usually notice better mpg, better response/performance, etc...

Also, a lot of people tend to get better mileage with higher 91-93 octane gas...

Ive gone through all the fuel companies in every octane for testing purposes. Ran them all consistently for a month and nothing has ever changed. LTFT are disabled completely. He told me he did a full street tune on it. I did ask for data logs

 

[06MonteSS]

Ah, so he did a speed density tune on it... why?? You don't have a monster build over 600/650+ hp, so a speed density tune is not necessary at all... You want to use the MAF sensor and long term fuel trims to adjust airflow/fueling, by re-scaling the MAF sensor table...

My educated guess is on a fuel issue, and that tune that was done...

 

[RDF1]

This would be a good time to get your own tuning software.

 

[JamalTheSilverado1965]

Ah, so he did a speed density tune on it... why?? You don't have a monster build over 600/650+ hp, so a speed density tune is not necessary at all... You want to use the MAF sensor and long term fuel trims to adjust airflow/fueling, by re-scaling the MAF sensor table...

My educated guess is on a fuel issue, and that tune that was done...

I’ll see if I can get the logs and maybe something catches someones eye

 

[JamalTheSilverado1965]

This would be a good time to get your own tuning software.

Yeah, I thought about it, but BTR had told me strictly dyno or street tunes no flash tunes so I never bought a Diablo or anything

 

[RDF1]

Yeah, I thought about it, but BTR had told me strictly dyno or street tunes no flash tunes so I never bought a Diablo or anything

You cant change anything you need to change with a Diablo or any type of handheld tuner.
You would need EFI Live or HPTuners to be able to get down in the weeds on this stuff.

 

[RedSLEd]

Bigger/heavier tires will hurt your mileage, as others mentioned. What gears are in the truck? Tall tires and tall gears is not a good combo. Was the speedo corrected for your taller tires? If not, your calculations are going to be way off.

 

[GOAT721]

i know its not the solution to the actual problem of a massive drop in mpg for a mod that shouldnt have, but you will get much better MPG at 60-65 rather than running 75 the whole way.

 

[Zeeman]

Any load in the bed, and is it covered? A bed cover gives much better aerodynamics. . . .

 

[EdgecrusherXES]

Any load in the bed, and is it covered? A bed cover gives much better aerodynamics. . . .

Bed covered beds are marginally better aerodynamically. The cab already stands in the way of the bed plus the bed creates a pocket of turbulent air that keeps the air flow off the tailgate. Adding a bed cover the biggest gain you will see is in noise reduction that the bed creates which is hardly detectable under 80mph. When you start getting faster the buffeting sounds if you pay attention gets a little louder but these trucks have a lot of sound dampening either way. Adding a bed cover made such a little change in fuel mileage I could argue that my driving style has more noticeable effect of fuel economy than the bed cover.
Bed covers are just good for turning your bed into a trunk and looks. Honestly that is why I got mine to carry stuff in the bed and have some barrier for weather changes.

 

[LiftedBurb]

i know its not the solution to the actual problem of a massive drop in mpg for a mod that shouldnt have, but you will get much better MPG at 60-65 rather than running 75 the whole way.

 

[06MonteSS]

Bigger/heavier tires will hurt your mileage, as others mentioned. What gears are in the truck? Tall tires and tall gears is not a good combo. Was the speedo corrected for your taller tires? If not, your calculations are going to be way off.

yeah, forgot about that too.. bigger, heavier wheels/tires will kill mileage... and as RedSLEd mentioned, if they did not calibrate your tire size correctly to correct your speedo, then that will also definitely contribute to the issue...