I just bought the 3872 programmer and went through the initial updating and install last night. I wanted to find a large thread to post my impressions, so back up to the top this one goes. See my signature for my setup. I'm running the stock 32" tires into the ground at 48k miles on them, and I wanted to get the inital updating and install of the program before my 37" x 12.5" x 17" Nitto Trail Grapplers get thrown on tomorrow morning. The rig is stripped down to be as light as possible right now so I could get a good feel of the difference in how it ran... plus it's hot and humid in MD at the moment: stock front bumper is chopped to a stubby, rear bumper removed, rear seat removed, top down, doors off.

First thing I did is plug the programmer into my computer (after downoading and installing Superchip's "Spark" software) and allow it to update. Took five minutes and went through without a hitch. Plugged it into the JK, following the clear on-screen prompts, and installed the 87 Octane tune—nothing else. Saving of stock files took maybe eight minutes... rewriting the 87 Octane tune took another five, perhaps. I didn't change any other settings (gas pedal response, etc.) other than that.

Impressions are lackluster as of yet, but my commute to work is short and low speed. I imagine after some highway driving today I'll notice a little more pull in the lower RPM range in 5th and 6th gears, but we'll see. The 87 Octane tune definitely changed the gas pedal response, too. It's still delayed, but it seems to ramp-up the rate at which it opens the throttle. So, a 30% depression of the pedal in stock tune now feels like 40-50% depression with the 87 Octane tune. I'll do more fiddling around with it at lunch today, but I was really hoping to get rid of the delay in response (which is very apparent!). Going into the vehicle settings with the 3872 and changing the specific pedal response should help with that.

Tomorrow morning, the 37s will be installed and I'm going to revert the tune back to stock for a few weeks: I want to see how the JK handles the meat in stock trim. Then, as the real test, I'll program Superchip's 87 Octane tune back in to see if I can maintain 6th gear any easier. Maybe the 91 or 93 Octane tunes would show more results, but I won't be running with them installed for any length of time greater than it takes to burn through a few tank fulls... my wallet wouldn't be able to take the abuse, I reckon.

So, 2012 running the 3872: no issues here.

 

I am on the fence of purchasing this. My question is will it be worth it? The wife is complaining because we added a lift bumper and soon the winch and lost mpg 18.9 down to 16.9-17.3. I have a 2014 jku Sahara with 3.73, 2.5" Teraflex lift and rockhard full width bumper.

 

I have one with a 09 auto 34" tires. It made a huge difference to me just setting for 34" tires and 91 octane. Shifts better and speedo is dialed in. After a full tank I gained about 1.5 mpg but need to shell out for 91. I don't thing the gains would be huge on a manual.

 

I'm actually running around 1.5+ mpg higher than before on the 91 tune(13-15 before, 15-16.5 now), vice the stock tune, on my '12 stick. Love the way it pulls now, and I especially love that crawl tune. Definitely makes crawling easier on the clutch, without having to feather it as roughly, or as often.

 

What size tires???

 

I went from about 19.2L/100km to about 14.6L/100km using the mileage tune and setting the tire size.

I did disable the pedal response boost, I find the pedal response in the JK to be laggy but after flashing it, the 6 speed was insanely jerky and annoying to drive. Its like the first couple inches are dead pedal and then BAM flooring. It was impossible to drive in first or 2nd without jerking the Jeep constantly.

 

stock tires. Since I bought it new it seems to run 2600rpms at 65-70.

 

I would think that unless you run bigger tires and require to adjust the tranny shifts points, the flashcal or flashpaq aren't worth the expense...

 

thats what im trying to figure out because I could tube the engine better to get things running a little better.

 

Since the flashpaq is advertised as adding 30HP and 30lb-ft, it is doing far more than just changing shift points and tire ratios. It's literally reprogramming the engine to work more efficiently and produce more power(you'd be surprised just how bad the stock tuning can be on some vehicles. Some, are unbelievably bad.). With more power and torque being produced by the engine, you'd need less fuel to do the same work.. So it only stands that by reprogramming, that theoretically fuel efficiency would have to go up.