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TL;Dr:
Compared my buddy's stock JTRD with 4.56 gears to my tuned JTRD with factory gears. Both on 37" KO2s.
1. Power to the pavement: Tune.
2. Normal acceleration from stop: 4.56s.
3. Cruising at 45 MPH: Tune
4. Cruising between 65-80: 4.56s
Not always satisfied with the tune on my stock geared Rubicon diesel with 37" KO2s.
Granted it's my daily work truck and usually has about 3-400lbs in the bed, but still. 500+lbs of torque I guess I was expecting 6 second 0-60 times with no discernable turbo lag.
I remember driving it around after installing it. Acceleration felt telepathic as if an unseen force was pulling the truck forward. Woohoo! This was what I signed up for! Then aftera while it felt like performance was slipping. Was I just getting jaded having all that disposable power all the time or was the computer figuring out a way to detune the tune?
My driving habits are 97% driving Ms Daisy and 3% pedal to the metal but when I get on it I expect PAYMENT IN FULL. After months of pondering and a couple really lackluster pulls, I decided to contact the tuner. I was told there was a portion of the PCM that would overwrite some throttle and I believe trans inputs, and that I needed an alfa obd tool and a $50 app to unwrite it.
Has anyone here done this? Is there a tutorial? There's a bunch of devices and apps and I'm not sure where to start.
In the meantime a buddy with a '22 JTRD (mine's a '21) with the same tires gets 4.56 gears installed and I want to know the difference in characteristics because I've always believed my Jeep would benefit significantly with regearing, so I took his for a spin, put it through a few paces and the results were interesting. I compared several driving modes:
1.Off the line WOT acceleration.
2. Normal acceleration from a stop.
3. 45 MPH cruising.
4. 65-80 MPH cruising.
1. My very first surprise was that when it comes to performance; gears don't even begin to compensate for a tune. The raw power on tap with the tune never gave the regear even a fighting chance. Night and day difference.
2. The regeared engine definitely feels it's performing more effortlessly off the line under normal acceleration. No hint of lugging. A happy engine doing a happy job. I believe there's a lot of fuel savings going on here with the 4.56s.
3. If there is a place where the stock gears with a tune shines, it's here. 8th gear @ 45-55 MPH in this configuration will likely yield the best MPGs of any other. It's the sweet spot and I believe if you gassed up and pulled onto a flat 45-55mph road with no contrary wind and no stops, you wouldn't have to gas again for another 600 miles. This is the only place I believe the tune alone provides any economy and that is undermined somewhat at higher speeds and accelerating from a stop.
4. I'm going to blame the factory gearing at these higher speeds for not allowing the benefit of more power to be brought to bear against the increased wind resistance. Whether accelerating from a stop or highway cruising, the tune does not perform well under 2000rpms. Not that the lugging can't be overcome with more pedal, but the high vacuum effortlessness in the +2000rpm range is not there. Yes the rpms were higher by a couple hundred and yes the diesel is a supposedly low rpm performer with full torque on tap well below at 1600rpm, but it's apparent the engine runs much more efficiently under load at higher rpms.
Now, if I can only get my hands on a JTRD with 37" KO2s and 4.11 gearing...
Compared my buddy's stock JTRD with 4.56 gears to my tuned JTRD with factory gears. Both on 37" KO2s.
1. Power to the pavement: Tune.
2. Normal acceleration from stop: 4.56s.
3. Cruising at 45 MPH: Tune
4. Cruising between 65-80: 4.56s
Not always satisfied with the tune on my stock geared Rubicon diesel with 37" KO2s.
Granted it's my daily work truck and usually has about 3-400lbs in the bed, but still. 500+lbs of torque I guess I was expecting 6 second 0-60 times with no discernable turbo lag.
I remember driving it around after installing it. Acceleration felt telepathic as if an unseen force was pulling the truck forward. Woohoo! This was what I signed up for! Then aftera while it felt like performance was slipping. Was I just getting jaded having all that disposable power all the time or was the computer figuring out a way to detune the tune?
My driving habits are 97% driving Ms Daisy and 3% pedal to the metal but when I get on it I expect PAYMENT IN FULL. After months of pondering and a couple really lackluster pulls, I decided to contact the tuner. I was told there was a portion of the PCM that would overwrite some throttle and I believe trans inputs, and that I needed an alfa obd tool and a $50 app to unwrite it.
Has anyone here done this? Is there a tutorial? There's a bunch of devices and apps and I'm not sure where to start.
In the meantime a buddy with a '22 JTRD (mine's a '21) with the same tires gets 4.56 gears installed and I want to know the difference in characteristics because I've always believed my Jeep would benefit significantly with regearing, so I took his for a spin, put it through a few paces and the results were interesting. I compared several driving modes:
1.Off the line WOT acceleration.
2. Normal acceleration from a stop.
3. 45 MPH cruising.
4. 65-80 MPH cruising.
1. My very first surprise was that when it comes to performance; gears don't even begin to compensate for a tune. The raw power on tap with the tune never gave the regear even a fighting chance. Night and day difference.
2. The regeared engine definitely feels it's performing more effortlessly off the line under normal acceleration. No hint of lugging. A happy engine doing a happy job. I believe there's a lot of fuel savings going on here with the 4.56s.
3. If there is a place where the stock gears with a tune shines, it's here. 8th gear @ 45-55 MPH in this configuration will likely yield the best MPGs of any other. It's the sweet spot and I believe if you gassed up and pulled onto a flat 45-55mph road with no contrary wind and no stops, you wouldn't have to gas again for another 600 miles. This is the only place I believe the tune alone provides any economy and that is undermined somewhat at higher speeds and accelerating from a stop.
4. I'm going to blame the factory gearing at these higher speeds for not allowing the benefit of more power to be brought to bear against the increased wind resistance. Whether accelerating from a stop or highway cruising, the tune does not perform well under 2000rpms. Not that the lugging can't be overcome with more pedal, but the high vacuum effortlessness in the +2000rpm range is not there. Yes the rpms were higher by a couple hundred and yes the diesel is a supposedly low rpm performer with full torque on tap well below at 1600rpm, but it's apparent the engine runs much more efficiently under load at higher rpms.
Now, if I can only get my hands on a JTRD with 37" KO2s and 4.11 gearing...
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