Mike, You speak about a RPM sweet spot for your Jeep at 2300 rpm. I've got a 2000 TJ with 30" tires and stock 3.07 rear end. How do you figure the sweet spot? I have to be doing 90 to maintain 23/2400 rpm .
Thanks JD 2K-TJ
There are some simple truths...And the dogs know what they are." Joseph Duemer
After the sweet spot talk....I can be in the sweet spot in my stock '02 doing 115/120 in 4th...but I have to be doing 130kph in 5th to be in there. Which isn't a problem on the 400 highway here...but any benefit of being in teh sweet spot for gas efficiency got killed by the excessive speed and lack of aerodynamics.
That's what I was trying to figure out. I try to stay in the right hand lane and do 55/60 mph. I figure that's where I'll get best mileage on local freeway. Even in 4th gear I'm only turning 1900/2000 rpm. I'm just wondering how much the 3.07 gears have to do with optimal fuel consumption + RPM load VS say 456 or 488 gears and how to best determine that sweet spot.
JD 2K-TJ
There are some simple truths...And the dogs know what they are." Joseph Duemer
On my 258, 2300 rpm or so seems to be a place where just a twitch of the gas pedal is needed to keep the speed against wind or hills and the pedal is about 1/4 way down.
I was told that is the area these engines reach their top timing advance or maybe peak torque and any more is just pouring fuel at her to work harder. It comes up to 2300 easy with a light pedal, higher means a lot more pedal down. 2800 is 2/3 down, etc.
Hard to explain.....
I have owned 4 bangers with a sweet spot of 3300 rpm.
If I run in 5th gear at 65 with my 33's and 3.31 gears, I am turning
1600 rpm or so which lugs the engine. I have to use a 'lot' of gas pedal to make adjustments for wind or hills. Hey, I have lots of power to run at those rpm at 65 mph, but it comes down to the pedal needed. Every time I have to floor it to hold against a gust of wind vs the twitch needed in 4th, well.... This burns way more gas.I can easily get an extra 4 or 5 mpg by staying in 4th gear on trips.
65 mph also seems to be a wind sweet spot for the CJ/Wranglers The resistance is an exponential increase and getting up into the 70's, well.... Just think on where your gas pedal is physically sitting to figure your consumption.Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT'sJD wrote:
The wind resistance increases exponentially.
65 mph or 100 kph seems to be a 'sweet spot' for that too.Mike
SB wrote:
Ok, That I understand. I noticed this morning that at 60mph in 4th I'm running at 2000 rpm with no strain. If everybody is running around town in 5th gear at 40mph no wonder their gas mileage sucks... Now if I could just reprogram that idiot light... Thanks Again JD
JD 2K-TJ
There are some simple truths...And the dogs know what they are." Joseph Duemer
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