Dave01 wrote:
The rpm numbers GDE gave you are at 80, but even at 65-70 you'll be well into the 2000 rpm range while my Liberty CRD is just hitting 2000 rpm at those speeds, maybe 2,200 at 74 mph. That diesel would like to cruise the highway at 1,800 rpm for best economy, stay out of the turbo as much as possible. I think it would still tow great with axle ratios that kept the rpm down, though I looked and the max torque happens in the mid 2000's so that's probably why it's geared that way, I think it has 3.73.
From what I read it is a 3.73 for the CRD and V8. I have been monitoring RPMs and MPG with a ScanGaugeII, but I have a feeling the readings I am getting are off a bit. My theory is that since the readings on the EVIC is known to be unreliable (hand calculated MPG is a few miles off) the same goes for the readings it is getting on the SGII. I read somewhere that some of the tunes improve this and you end up with a more accurate reading on the EVIC.
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I'd look at putting the largest diameter tires you can fit on it to get rpm down, but you still need light weight, low rolling resistance tires or the advantage will be lost. Ask GDE if they can compensate for the bigger tires in their tune, not sure.
That is interesting and logical I guess. I wonder how much of again that might be. If I were to get a lift (which I want to do eventually) to fit bigger tires I am wondering if any gains will be a wash. Also, as I understand it, the gains would be only for cruising. You would strain the engine a bit more off the line, so the MPG there will suffer there, right?. There has got to be a formula to calculate MPG gains based on size of tires, but I have never come across that.
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I've thought recently about trading my Liberty CRD for the Grand diesel, just to get the fancier interior and a bit more room. There is one for sale nearby that I might go and test drive. But, with that kind of loss of mileage I'd have to think twice, plus I really enjoy the low rpm, smooth cruise of the Liberty on the highway.
I can't speak for the Liberty, but the grand is nice, and since they came as limited models they have all the trimmings: Nav, leather, backup camera, TPMS, Sat, etc. But from what I hear, the MPG difference on the two is substantial. The GC does have the top of the line Quadra Drive II in its four wheel drive, but it is permanent, and I am sure you can get some gains by running it 2WD for the highway on the Liberty.