Looking to actually gain some MPG

[sdog4127]

 

This but I would recommend using at least 89 octane. The Direct Injection and High Compression ratio will thank you.

I have found by watching scan data, the higher octane fuel in the L83 5.3 (non-flex) will actually improve ignition timing by several degrees. This is because these engines monitor knock extremely tight. These are relatively really high compression engines and because of that they WILL benefit from high octane only because of the DI. Direct injection delivers a much cooler burn because the fuel is sprayed directly into the CC and creates a cooling effect; therefore can handle a bit more cylinder pressure without detonation. That transmits directly to fuel efficiency. Of course if you continue to squish the skinny pedal or have windy conditions the gains are moot. But under normal driving I see 35degrees of advance vs about 28 with 87 octane. Oh - and if you don't have a flex fuel or tune for alcohol STAY AWAY from E10!!!!! If the software can't identify the level of alcohol in the fuel it treats it like normal fuel and reads the A/F mixture to be lean and results in a reduction in economy. FF engines can compensate, but I don't see many of them in the K2's sine the 2014 MY.

HTH

SMH

 

 

 

 

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[jenkins12]

Understanding that exhaust and intakes are not going to pay for themselves by improving MPG (at least in the near future), is there an increase in performance? I am less concerned with the sound as I would be in the potential increase in performance. Thanks all!

[fbachman]

Understanding that exhaust and intakes are not going to pay for themselves by improving MPG (at least in the near future), is there an increase in performance? I am less concerned with the sound as I would be in the potential increase in performance. Thanks all!

My experience says that exhaust and intake, by themselves, will yield very incremental performance benefits.

 

It's there, but hardly measurable. If it's 1% I would be surprised.

 

It may SOUND a whole lot better tho.

 

Best you can do with a stock engine is a tune. I am guessing you'll see maybe 10% on peak hp at best.

 

Intake, Exhaust and tune together? MAYBE 12%.

 

Again, that's probably approaching a $1000 expenditure for all 3, maybe more depending on the tuning strategy you decide upon. That's significant $/hp already, approx $25 per additional 1 hp. (Assume 380HP out of the box, add 40hp. $1000/40hp = $25 per horse.)

 

Up to you...

 

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[jenkins12]

My experience says that exhaust and intake, by themselves, will yield very incremental performance benefits.

 

It's there, but hardly measurable. If it's 1% I would be surprised.

 

It may SOUND a whole lot better tho.

 

Best you can do with a stock engine is a tune. I am guessing you'll see maybe 10% on peak hp at best.

 

Intake, Exhaust and tune together? MAYBE 12%.

 

Again, that's probably approaching a $1000 expenditure for all 3, maybe more depending on the tuning strategy you decide upon. That's significant $/hp already, approx $25 per additional 1 hp. (Assume 380HP out of the box, add 40hp. $1000/40hp = $25 per horse.)

 

Up to you...

 

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Is there one tuner that is better than another? I had a tuner in my diesel but never in any of my gas vehicles. I hear people throwing around the "Custom Tune" phrase. Who is creating these custom tunes and what are they based off of? (I am pretty new to this forum so if this subjects has been explained to death, my apologizes! Kindly point me in the right direction)

[TxTruckMan]

My $0.05

 

I haven't read all of these posts, so if this has been covered, please forgive me.

 

Much of this comes from personal experience.

 

-Our trucks are, primarily, tuned for emissions first, performance second. With modern engine controls and good engineering and solid design, modern engines will, simultaneously, achieve both extremely well.

 

-The issue of increasing fuel economy comes down to shifting the balance back and forth between emissions and fuel economy. Oddly enough, fuel economy and emissions move opposite of one another to some degree. An engine that meets emissions, may not have the best fuel economy that could be achieved by ignoring emissions, all other things being equal.

 

Unfortunately, if you want better fuel economy, the emissions will suffer. Thus, a tune will give you the most improvement --- at the expense of emissions. I do not say that as an environmentalist, but as someone who recognizes that, at the end of the day, the engines are tuned for emissions compliance FIRST, and economy SECOND. The 8 speed automatic trans is there for more than one reason. It's easier to control emissions if you keep the engine in an "rpm sweet spot" during the epa cycle. Many gear ratios allow you to do that more readily. In fact, I would argue that that is the ONLY reason AFM exists: the EPA cycle. It goes to an rpm sweet spot AND shuts off 4 cylinders. Emissions panacea.

 

Forget air intakes and exhaust systems and such to increase mpg. They help incrementally at best ( the improvement realized is lost in statistical noise and uncertainty of the measurement). That's how small it is.

 

If you really want a noticeable improvement in mpg, ya got to go into the timing map. This is done with a tune. At that moment, you will, most likely, no longer meet emissions compliance. Not that we care about that, necessarily---but GM has to when they comply the vehicle/power train.

 

Interestingly, tuning will get you better mpg, and probably better performance as well, even if you're targeting mpg alone. As you can only push timing so far given the fuel octane ratings available, you're probably looking at 1.5-2 mpg improvement, at best, without changing out major engine components.

 

If you want more than a tune can offer, in terms of mpg, now you're talking about cams and major engine components.

 

Now the economics. Tunes cost money. You're buying approx 1.5mpg for the cost of the tune. It will pay for itself at some point to be sure. You can do the math on that one for your particular situation.

 

My (53 year old) opinion: It is what it is. Enjoy your truck. You bought it knowing it wasn't a fuel sipper, although it is quite remarkable that a huge truck with a 5.3l engine can get 17mpg in suburban driving all day long. Just drive and enjoy. They are great vehicles.

 

Cheers !

I'm not sure that this is entirely true. Fuel Economy and Emissions are tightly coupled. If you spend less fuel, you will release less emissions. The struggle OEMs have is to produce more POWER while using less FUEL which leads to less emissions. Through a tune you can certainly gain more HP, but likely at the cost of fuel economy. There's a balancing act for sure, but it's between HP and FE/emissions.

[fbachman]

I'm not sure that this is entirely true. Fuel Economy and Emissions are tightly coupled. If you spend less fuel, you will release less emissions. The struggle OEMs have is to produce more POWER while using less FUEL which leads to less emissions. Through a tune you can certainly gain more HP, but likely at the cost of fuel economy. There's a balancing act for sure, but it's between HP and FE/emissions.

I guess I should not have expressed it in that way. They are closely coupled, as you correctly indicate. In most instances, they are inversely related however.

 

That would have been a better way for me to express it.

 

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[TxTruckMan]

I have found by watching scan data, the higher octane fuel in the L83 5.3 (non-flex) will actually improve ignition timing by several degrees. This is because these engines monitor knock extremely tight. These are relatively really high compression engines and because of that they WILL benefit from high octane only because of the DI. Direct injection delivers a much cooler burn because the fuel is sprayed directly into the CC and creates a cooling effect; therefore can handle a bit more cylinder pressure without detonation. That transmits directly to fuel efficiency. Of course if you continue to squish the skinny pedal or have windy conditions the gains are moot. But under normal driving I see 35degrees of advance vs about 28 with 87 octane. Oh - and if you don't have a flex fuel or tune for alcohol STAY AWAY from E10!!!!! If the software can't identify the level of alcohol in the fuel it treats it like normal fuel and reads the A/F mixture to be lean and results in a reduction in economy. FF engines can compensate, but I don't see many of them in the K2's sine the 2014 MY.

HTH

SMH

 

 

 

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Well, my experience disagrees with you. In my 2014 with the 5.3L I conducted an experiment on the use of regular or high octane fuel. I went several months running regular 87 octane gas and averaged 17.5 on my normal commute. 2-3 tanks per month. Then for another several months (3-4) I used 93 octane fuel to see if there was a difference. Nope, still 17.5 mpg average. So I switched back to regular ole 87 octane.

 

Now I wasn't towing or anything. Just regular around town and highway driving. Several members have mentioned seeing timing retard when using 87, but I haven't seen that it impacts fuel economy in any noticeable way. Of course YMMV.

[TxTruckMan]

FWIW, I have never heard of anybody being able to "mod" a newer vehicle to achieve better fuel economy. The OEMs squeeze every tenth of a MPG they can out of these trucks as they have to meet CAFE requirements or face hefty fines. If there are tenths to be gained, the OEMs have already done it.

 

The bed cover was a valid mod years back, but OEMs have since added the "spoiler" to the rear of the tailgates to achieve the same aerodynamic effect.

 

The best advice I have for people that want better fuel economy is to NOT mod your truck at all - stay completely stock, especially your tires - and research hypermiling. Changing your driving habits will have the biggest impact on mileage.

 

My daily commute is 45 miles round trip. Probably 40/60 city/highway. I'm nearly all city on the weekends. I average 17.5 to 18 MPG using my normal driving style. Every once in a while I used to fool around with hypermiling and could easily get 20-21 mpg on a tank of gas over the same commute. This was when I had my 5.3L I tried twice with the 6.2L, but I couldn't get above 19 on a tank.

 

The only mod I would explore would if you're looking for improved mileage is a product by Range. Everybody knows about the Range device that disables AFM in our trucks. Well they also have a similar device that forceably enables AFM. I think AFM runs about 10%-20% of the time normally. I saw a while back that they had one device that enabled it about 50/50, and another that enabled AFM 80-90% of the time. I have never heard of anybody trying one out.

[Zachlovesfood]

Has anyone thought about an under drive pulley for fuel efficiency? From what I understand, the engine doesn't have to work as hard to reach any given speed, compared to the stock pulley... I hear it improves performance too. Thoughts??

 

 

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[Silvern Sentry]

Has anyone thought about an under drive pulley for fuel efficiency? From what I understand, the engine doesn't have to work as hard to reach any given speed, compared to the stock pulley... I hear it improves performance too. Thoughts??

 

I think any such mod that will run in the $1000+ range will take a real long time to see any kind of return on that investment. Like years long.

 

Best way as others have said is your driving habits. ex) getting up to speed and coasting is more efficient that slowly getting up to speed. I Live on Vancouver Island though so to me fuel efficiency is like a mythical dream from a far off land. SO much stop and go traffic here.

[SouthernSilveradoGuy85]

Nothing you buy will gain MPGs and if it does it's not enough to notice, especially talking about enough gas to save enough that will have the product pay for itself.

 

Honestly the best way to improve or get good MPGs (especially on a truck) is to keep the tire pressures equal, more PSI will give you better MPGs but will hurt the ride and then the biggest way to get as good of mileage out of it is your driving. I remember my truck got pretty good gas mileage in town before I had the exhaust done so I babied it and could get about 18 as an all town average in the summer. After the exhaust was done I'm lucky to get 16 in town average in the summer because the exhaust got me to revert back to some of my old/normal driving style. It's still a lot more calm compared to 10+ years ago, but I sure don't baby it anymore. Part of the low MPGs in town is the 3.08 gears which I do plan on regearing in the future. On the highway though I get great mileage, but also read that lower gear (higher #) doesn't effect MPGs on the highway. It gets decent mileage on the interstate, but it tends to stay in V8 mode where as on the highway going between 50 and 60 mph it goes into V4 a lot and helps with average mileage.

[Zachlovesfood]

 

I think any such mod that will run in the $1000+ range will take a real long time to see any kind of return on that investment. Like years long.

 

Best way as others have said is your driving habits. ex) getting up to speed and coasting is more efficient that slowly getting up to speed. I Live on Vancouver Island though so to me fuel efficiency is like a mythical dream from a far off land. SO much stop and go traffic here.

$1000+ range? I remember one thread in particular, where a guy spent $200 on a new balanced pulley. I'll see if I can find the link. I never followed up on that guys results.

 

 

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[Zachlovesfood]

Guy claims he gained MPG from under drive pulley. Although I do stand corrected, the pulley is $289.

 

http://www.gm-trucks.com/forums/topic/170181-L83-Underdrive-crank-pulley-installed%21

 

 

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[TxTruckMan]

Has anyone thought about an under drive pulley for fuel efficiency? From what I understand, the engine doesn't have to work as hard to reach any given speed, compared to the stock pulley... I hear it improves performance too. Thoughts??

 

 

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The theory is that a smaller pulley will make it easier to run the accessories (compressor, alternator, water pump). The problem is that they then turn at a slower speed - not as designed. I believe that the alternator now runs with a clutch so that it only charges when the battery actually needs it. Same with the compressor. And I sure don't want my HVAC or water pump running at lower capacity. And our fans our now electric, so I don't see any real benefit here. Again, OEMS are looking for every tenth of a MPG, which is why the already made these design changes.

[Zachlovesfood]

The theory is that a smaller pulley will make it easier to run the accessories (compressor, alternator, water pump). The problem is that they then turn at a slower speed - not as designed. I believe that the alternator now runs with a clutch so that it only charges when the battery actually needs it. Same with the compressor. And I sure don't want my HVAC or water pump running at lower capacity. And our fans our now electric, so I don't see any real benefit here. Again, OEMS are looking for every tenth of a MPG, which is why the already made these design changes.

I understand, and that totally makes sense, since it would be turning at a slower speed. I'm not too knowledgeable on the subject, so what you've said leaves me with a few questions.... Especially since I was considering doing a pulley/cam upgrade down the line.

So, first question, am I wrong to assume that the voltages that power the electronic parts on our trucks are controlled by the computers installed?

If so, that means the currents would remain stable unless lowered drastically, however your alternator would be working a bit harder to compensate.

Which leads to my second question. To my understanding, there's an alternator upgrade available through a GM parts manufacturer. I'm assuming that would be more efficient in keeping that battery charged, as it wouldn't have to work as hard as the base alternator.

That being said, despite the cost of a new alternator, new pulley(s), and new belt(s), would it be effective?

The link I posted above has a few people claiming to have good results from the pulley alone, which include performance and MPG. I would be doing the upgrades for performance and if my assumptions are correct, voltage efficiency (obviously not financial efficiency haha). That said, in my case, this wouldn't be a mod for MPG.... Which is actually contrary to the main subject... Sorry about that.

 

 

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