At the advice/nudging of several very helpful fellow members here, I picked up a Superchips Flashpaq F5 tuner which has unlocked a TON of cool tweaks and features for us. Chief among them, is the engine tuning which is the main thing I want to talk about here. I was hoping the tuner itself would be enough, and it definitely helped, but I was still unable to maintain highway speed. Over the weekend, I finally got a chance to install my Yukon 4.56 gears (well so far I did the rear axle) and this helped a LOT! Brought my highway cruising rpm up from 2000 to 2400 where this little mill can actually do some work.

So far, I've done three things yesterday for the first time in this Jeep...

First, I actually passed someone on a 2 lane highway! He was doing 65 in a 75 and normally I would just have to wait behind him, but no, not this time, I actually passed him in a very reasonably short distance.

Second thing, I used cruise control at 75 without losing speed or downshifting for a 30 mile round trip! Now I did notice it never turns "ECO ON" there, so it is working just about as hard as it can. In fact, I checked on the data stream with the tuner and it sits at >93% engine load constantly at this speed. Now that I think about it, I need to watch that and see exactly what load percent turns that indicator on...

Third thing, I actually got Torque converter to lock-up before 50mph in D which will be great for in town driving. Again I'm curious at what minimum speed this is possible now, my experience with other Chrysler vehicles is about 42-45 mph.

I have probably re-flashed this Jeep a dozen times since purchasing this tuner, I have so far tried the 87, 91 and 93 tunes several times and the mileage XS tune briefly but not the Tow or Crawl. I like the modified shift points but I'm not impressed by the pedal response mods, I think they are gimmicky. Yeah it makes it "feel" more responsive in town at first because it reacts with less pedal movement, but its not like I ever use anything past half throttle anyway and it does nothing for highway driving so I keep this setting on stock.

So far as I can tell, the 91 tune is useless, I think it actually has less power. Even after the gear change, it cannot even get to 75 mph, I mean maybe if I pushed it hard enough but its noticeably less power maybe even less than stock. To be fair, I haven't tried it with 91 octane gas, only 89, has anyone else experienced this? The 87 and 93 tunes both improve the overall performance and its tough to tell if one is better than the other. Is it possible that lower octane fuel is holding the 91 or 93 tune back? I don't know of anywhere around here I can even get higher than 91 so what about 87 with some octane booster? I'll try that next fillup...

Has anyone else experimented with the different flashes and octane combinations?

 

I tried all the tunes with the Flashpaq F5, was biggest waste of $ in my opinion but was worth trying out none the less to see if I was missing anything worth having. I ran each octane tune over the course of a week with corresponding gas. Nothing really noticeable. I ended up going with the 87 tune with 87 octane gas.

You have to try to eliminate the placebo effect. What I ended up doing was running quarter mile drag races from 0-60mph to try and see which tune with which octane gas got me to 60mph the fastest. Totally, disappointed that ended up being the 87 tune with 87 octane, if I hadn't taken the actual times and compared them, the placebo effect would have gotten the best of me. The eco tune, just made my JK feel sluggish.

The best things the Flashpaq provides in my opinion are the ability to change tire size, and gear ratios when re-gearing. If you were having rpm and shift problems at highway speeds, that is usually due to having larger tires installed without updating the ECM via Flashpaq or other device with the increased tire size.

When adjusting for tire size, I like using a portable GPS which displays your current speed and matching that up against your speedometer. I have 35s BFG KO2's. Actual measure=34.5in. I found Flashpaq set at 33.75in size tires gave my speedo most accurate reading when compared to portable GPS device, which in turn will provide proper shift points at proper rpms.

 

I agree 100%, you have to remove the placebo effect which I think is a lot of what the pedal tunes are just makes it "feel" faster without actually helping anything so I'm hoping that watching the engine load at highway And keeping a close eye on fuel economy will be most telling. But I can't say for sure that it does make some difference it wasn't until I got the super chips that I could accelerate in overdrive at all.

You're also correct about the secondary reason I purchased it was to program the gear ratios and just as you described I used my phones GPS to tweak my tire size until my speedometer is dead on with the GPS. My speedometer was very accurate before, so the tire size must have been programmed in it just didn't have enough power to turn them with stock gears.

 

It's odd that you guys didn't feel the lag taken out of the pedal, maybe that's a manual thing? But I've enjoyed the Superchips for my 3.8 long before I did gears. I run the tow tune with 87 gas. I think the 87 tune with 87 gas yields better mileage but it was a struggle with 35's, hills, and the 3.8.

I ended up programming gears via Jscan but I keep the Superchips as my main tuner since it was around and available long before Jscan.

 

So you only re-geared the rear and then went out and did all this??? Don't you have to do both front and rear?? And I thought all this time I wanted less rpm's at cruising speeds.

 

You may think that less RPM at cruise would result in better efficiency, but you really want to keep the engine in it's power band for better efficiency. If the RPMs are too low, the engine will struggle to maintain, and will result in lugging/bogging and overall not the best driving experience.

 

Yes, I bought the kit to do both but ran out of weekend. I didn't back it out of the shop until 2AM Easter morning. Took a little longer than I had naively hoped. Obviously can't use 4wd until I do the front axle.

 

Definitely if I program it with the "superchips pedal response" enabled it makes a difference in the feel of the pedal but the effect wears off quickly with road speed and I have no complaints about the factory pedal feel. You may be right about the different transmissions, a manual will let you roll a into the throttle a lot more than automatic.

 

It also took me two weekends to do it, but take the time and be patient with it. The break-in is the next toughest part- heat cycling the gears and recalling to do it when you first pull a trailer. It sounds like you're already enjoying the benefits of the power but I'm curious what happens with your mileage. Mine didn't change much, though I was hoping for a 1/2mpg increase since I wasn't running higher RPM's just to get down the road.

 

Yeah, I did a lot of reading and YouTube research before I started the job and felt I had a good idea what I was getting myself into, but I wish I could have started a little earlier in the day. But definitely, patience is a must. Much better to take a long time to do it right than to have to do it twice!

I am hopeful the mileage will improve too, and judging by the instant mpg on the dash it sure might but I'll have to run a tank or 2 through before I know for sure. Even if it doesn't improve mpg much, drivability is so much better it will still be well worth it.

Plus I got these gears from Summit on some kind of Covid-crisis end-of-year closeout or something, it was only $400 for the whole kit!