CaptainNapalm

I keep reading online people's fascination with tuners and in some instances their alleged ability to program a JK for better fuel consumption. For curiosity, I've followed a few of these threads, including some on this forum, and read various experiences on these tuners and how they relate to MPG improvements. It appears that some people note a significant improvement while others using the same tuner report negligible results, if any at all. So this got me thinking on how these tuners might actually work to gauge such mixed results and I'm wondering if anyone with some technical knowledge can chime in on this. I'm guessing that perhaps these tuners just reprogram your vehicle on how it responds to gas pedal use. For example, following a tune for better MPG, the vehicle will respond differently and accelerate much less dramatically when one floors the pedal to the metal. Of course this will keep your RPM's lower resulting in improved fuel economy. So if you fall in the category of a more aggressive driver you will notice note worthy fuel consumption improvements. On the other hand, if you are already a conservative driver and don't slam on the gas pedal, the tune would be of little to no benefit to you as there is no harsh driving it can filter and can't direct your RPMs to lower ranges than you're already doing on your own. I'm wondering if anyone knows exactly how these things work technically to improve your MPG. I initially thought it was just a hoax but there are just too many people online who claim they tracked improvements. Thoughts?

AngryRedBird

I've never attempted any sort of procal system or setup.. One thing I do know.. is if I have to take the jeep to the dealer.. they tend to flash the system or just plug into the system in order to check things out.. if anything needs to be updated, it's done then.. The jeep seems to run better afterward.. But every two years Maryland required all vehicles (Diesel exempt) to have their emissions tested.. in this case and when the tech plugs into the jeep in order to check for codes etc.. I feel they are or have done something.. the jeep doesn't seem as peppy anymore as compared to the plug in from the dealer.
On past jeeps, we've had the Jetchip.. (stage 1) which is an added bonus to horsepower and torque.. but we've since stopped using this chip on the grounds that we are more interested in the fuel economy.. Several times I've submitted a request to the makers of the jetchip to include a fuel savings option and not so much the horsepower aspect. Thou it's unclear if this was ever done, seeing how we never followed through to stage 2 or 3.. If it was really important to go fuel savings and if I had the green.. it would be a diesel swap..

Vladimer

I would drive somewhere in the middle I think, some days I am in no rush and drive conservatively, other days I am a rather aggressive driver. I notice a good increase in my MPG but haven't really noticed much loss in power... who knows what this black magic is.

Ultimately they could just have made the display show a lower number (l/100km), wouldn't be any wiser lol.

bombout800

A tuner isn't a magical mpg booster. You won't receive a huge boost in power, much less mpg without having your jeep tuned. The canned tunes won't give you a whole lot of benefit. You will see increased throttle response because they are able to increase the delay from the drive by wire. It's possible to see an increase but its also possible to see a decrease. If you have someone local who can datalog and street tune, that's where the increases begin. A typical dyno tune isn't real world, and only gets you numbers. Street tuning gives you real world driveability. For instance I don't know whether the tuners these days have any transmission control, but it would help a lot. Our 1-2 shift is very short and 2nd gear is super long. So if you take off slow and then try and hit the gas about 1/2 throttle, it shifts to 2nd and bogs down. When you try and baby it through the streets its very aggravating to drive. If we had control over this transmission and shift points, I think with the added abilities of the tuner, we could have very nice drivability with a small amount of increased power and mileage.

Jeepstin12

I will try to answer this with as many things as I know about modifying motors, which I haven't applied to my JK, but have extensive experience with other vehicles.

First, to get more power, you want more air and fuel going into the cylinder. This is achieved by also changing the intake, exhaust AND timing of the motor. The tuner can change the timing and fuel which will create more power but not exactly improve mpg. Whether or not you get an mpg improvement really depends on that motor design, gearing, drive line set up, etc. As for the timing, carbed motors were more fun as you would change out cams, port & polish heads, open up the throttle plate, swap out the fuel pump, exhaust, intake and possibly even the Pistons and rods (stroker motor). Today, it's intake, exhaust and and ECU.

Just about all tuners for the Jeeps aren't going to give you that "I can feel it" response. If you are looking for that, you want an S/C, turbo or he I swap. Consider if a tuner could give you 50 hp and 50 ft lbs torq., you lose a good bit of that in the drive train and wheel horse power is considerably less. Even if you get a full 50 hp at the wheel (which none do that I know of without other mods) you aren't going to feel much difference on a 5,000+ lbs. vehicle. Simple physics at this point.

Now, I modded a Volvo S60 T5 a few years back. I dropped about $5k in it to go from 247 hp & 250 ft lbs. of torque to 410 hp & 425 ft lbs. of torque, all out of a 2.3 liter inline 5 high pressure turbo. I also remapped the ECU, cold air intake, headers, exhaust, down pipe off the turbo, ported the heads and had them polished as well. All this dropped the factory 0-60 of 6.9 seconds to a new and improved time of 5.2 seconds, on a car hat weighed 3400lbs. Curb weight. This car taught me that Goodyear tires suck. And there wasn't a mustang that could touch it, which was really funny to see them get their asses whipped by a grocery getter.

MPG? Slightly better at around 1-2 mpg. It burned premium only prior to mods and after. I did the math for giggles. I would have to drive that car for about 15,000 miles a year for 27 years to see the return on fuel savings and counter effect the money spent in the mods.

I also did similar mods to a Buell lighting. great performance, an increase of nearly 40 hp and torque, but on a 300 lbs. machine. That, you can feel. It also sucked down more fuel. No fuel saving observed, the opposite actually. I eventually pulled the entire EFI set up, put on a carb a magnacharger, modified the airbox,, swapped out the cam, added fly wheel weights, straight exhaust and made it even meaner. It was meaner on my wallet too. Not just the parts, but it garbled even more fuel.

I did my Dodge Ram, a number of racing ATVs and now tinkering with my Wife's Volvo XC 90 V8. Also did a number of other builds with my uncle in his custom bike shop, another friend who owns a speed shop in Cali and so on. After all that wrench turning, tinkering, playing, etc., there is only 1 way to really get anything good. Change the motor. Swap or tear down and rebuild. But it starts there.

I hope this gives insight to what you are asking. In short, your gains are negligible with simply running a tuner even though there are many guys on here who swear to have significant improvements. For me? Every time I modified something, I took it to be run on a demo as I wanted the hard data, not just an opinion. There is another thread where I offered to pay for a dyno test and they guy didn't take me up on it as he knew as well as I his claims were BS.

If you want more power, you will spend more money than most plan on spending and the results can be rewarding, if done properly. If you are looking at doing this on the cheap ( tuner, intake, exhaust), in my experience and opinion, you are wasting your money and wish you spent it on other mods. Most often, if you see an improvement in mpg, it is offset for the need to run higher octane.

In short, there is no simple bolt on fix for any true gains. If mpg is a concern, don't modify anything (lift, tires, etc.). If power is the concern, do it right and you won't be disappointed.

Mark Doiron

No specific technical knowledge, but the bottom line is the MPG numbers you see quoted on the forums are not very reliable. The EPA has very strict standards in order to insure that MPG numbers posted on window stickers are reproducible. Not only is the test profile specified (speeds, AC settings, terrain, etc), but even the gas is tightly specified and controlled. However, you have no idea what someone on the Internet has done to control their MPG readings. With all due respect to the few diligent folks on this forum who have tracked their Jeep's MPG numbers since day one/new purchase, the truth is that those test results are still unreproducible because even if they drove the same route to work and the grocery store and so on, there still was no control of weather and air conditioner settings and so on. And they nor you have no idea if the gas purchased, even if purchased at the same station for the last seven years, was of exactly the same quality every time. In fact, there are different gases sold in different parts of the country during different seasons, so it's very unlikely that the same gas was used for every run of that particular Jeep.

These are important things to consider, when what you're looking for is a 4-5% change in gas mileage. Anyone claiming any more should just be summarily ignored because if they could get 3, 4, 5 MPG improvement, the car manufacturers would be all over that technology to incorporate it into their vehicles. Don't you think that Chrysler would much rather sell all of us Hemi's for an extra $3K if they could only meet those CAFE numbers?

Jeepstin12

JP Mag just did a great article on mods, pros & cons, cost, gains (or not). You should pick it up. October issue.

Chefbrujo

I have kn filter (not cai) dynomax exhaust and superchips flashpaq on my 2010 jkus. I would like to point out that when doing the math of mod cost vs long term savings cost, most people should not put too much weight on long term savings as all of our financial situations vary throughout our lives. If it takes several years mathematically to recoup money spent on mods, it does not mean that an extra $5-$10 bucks per fill-up does not help every week. If someone is struggling to have $5 in their pocket to eat something or to buy their kid something they need, then the tiny immediate financial savings is worth it. And becomes more worth it over time. I get the long term math stuff, just wanted to point out that our lives are equations with so many unforeseen variables that it may not be fair to dismiss the value of something like a small mpg savings. It's worth it to me, or i should say it was worth it since i recently changed my tune to 91 performance. Now the $300 spent on a flashpaq is well worth it in return for the performance gain. We all know the 3.8 is a dog but with a performance tune it is at least not such a lazy dog. And the throttle response is not the only noticeable improvement. While it is small, it is there. Switching from 87 to 91 octane in and of itself will supply a small improvement, the tune just maximizes that. Well worth $300 once for a lifetime of pleasure from my Jeep.

TheDirtman

People lie about performance to justify the money they spent on the programers. Car manufacturers are under a lot of pressure to get their MPG numbers up due to cafe standards. If it were as simple as doing a software update to increase the mpg by 2-3 they would surely do it.

holy_crap

My experience with my 2010 and a Hypertech was of no significant change in power or MPG. In fact, when I returned the Jeep to stock before trading it in, it seemed to accelerate better with the stock program, go figure. In my opinion, the biggest factor in MPG on these bricks will be driving style and vehicle weight. There is a reason why a stock Sport with the little 16" wheels gets much better gas mileage than a Rubicon with aftermarket bumpers and wheels.

Another thing to consider is the cost of these mods. Going with lighter aluminum aftermarket bumpers and armor will keep the weight down, thus theoretically yielding better MPG, but the added cost of the aluminum parts will negate any savings at the pump in the short to mid term. Same goes for the cost of a programmer, $300+ will take a while to make up on 1 MPG increase.