Any regrets ? - Page 3 - Jeep Wrangler Forum
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > JK Jeep Wrangler Forum > JK General Discussion Forum

Join Wrangler Forum Today


Reply
 
Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 10-19-2011, 09:37 PM   #61
Jeeper
 
cu in oz's Avatar
 
Join Date: Aug 2011
Location: South Coast of Massachusetts
Posts: 620
The 3.21's are great for a DD/light off road use and your milage will be in the low 20's. I'm back all around just about 20.4 mpg. I also have a light foot....just saying. At 62mph (100K) I'm turning about 1750 rpms...just guessing, could be 1800, but no higher. I usually run highway at this speed in the JEEP. Now the Volvo is another matter

The LSD is nice to have for snow.....you don't "NEED" it, but it would have been on my order if I had been filling out an order form.

I wanted a Sport "S" Sahara Tan 6spd H/D and my local dealer had mine on the lot.....it was love at first bite.

__________________
'11 Sahara Tan Sport "S" H/T 6spd
cu in oz is offline   Quote Quick Reply
Old 10-19-2011, 11:52 PM   #62
Jeeper
 
Rooster76's Avatar
 
Join Date: Oct 2011
Location: Indy
Posts: 817
Talking

Quote:
Originally Posted by recreate.me View Post
Awesome thread!

Rooster: Are you saying GET the 7 speaker sound system if you can live without the trunk space? or DO NOT get the 7 sub because its not worth the price based on sound quality ?

I have been reading a lot about LSD, what benefits would that have over not getting LSD?

and 3.21 is better for gas milage on a 2dr daily driver, no towing ?

Also, would getting the flame red make the jeep faster? because my flame red sunfire is way faster then my gfs white sunfire...

SOUND

Personally I can do without the sound upgrade, and would rather have the space in a 2 door. Honestly I wouldn't really care either way much in an unlimited. I've never driven one with the upgrade but the basic one was pretty good on the test drive for me. It's really all personal preference. The sub takes up about a backpack worth of space in the back that I don't want to give up.

LSD-Limited Slip Differential (a good upgrade)
If your a bit fuzzy on why you need LSD on a open differential I would watch this

All wranglers have a BLD -Break Lock Differential system standard . It works by the computer seeing that one tire is slipping and so the other side is getting no power. If the wheel is spinning it applies some break to that spinning wheel transferring a little power to the other side. Its not really super elegant but gets the job done if you stay on the gas.

Trak-Lok is what they call the Jeep LSD -Limited Slip Differential.
It is an upgrade for Sports and Sahara for about $250. ( Rubi's don't have the option as far a I know. It probably just cannot fit/work with the lockers) You won't notice the LSD is there if you have it under normal conditions. It works with clutch type of system which is prone to wearing out at around 50,000 miles depending on use. After that time you can have the disk replaced. Basically the same kind of concept as replacing break pads. It also requires a bit more maintenance in the way of having to add special oil to the differential (that big ass thing in the middle of your axles). It doesn't work at all if the wheel spinning is off the ground. It is really good for snow, rain or mud especially when new and on roads. It transfers about a quarter of the power to the no spinning tire when it is engaged by centripetal force. It's a pretty cheap option and probably worth getting. Unless your planning on running Lunch-Boxes (Not really sure what they are but I know it makes using them harder to put on with the LSD equipment in there). Or you can upgrade to better Eaton Detroit Truetrac LSD aftermarket option (Probably somewhere over a grand upgrade).

I guess while I'm on my soap box I'll talk about Ruibicon Lockers. They only work when engaged by a button (unlike LSD), and lockers only work in 4-Low under 25 mph. They are the $hit if your really stuck and not just hitting a patch of ice. They lock the axle and there is no wheel spin and full power to both tires.

This is at least my understanding from doing a bunch of research.

Rooster76 is offline   Quote Quick Reply
Old 10-20-2011, 12:06 AM   #63
Jeeper
 
Join Date: Jun 2010
Location: Southern California (Inland Empire)
Posts: 347
I have two regrets...

1) that I did not get the LJ. it was only made for two years but that extra room while keeping it a two door would be very nice.

2) wish I would have gotten an automatic since it is my daily driver

But even with the two regrets, I would not give up my TJ for anything.
darin.1701 is offline   Quote Quick Reply
Old 10-20-2011, 12:22 AM   #64
Member
 
Join Date: Aug 2011
Location: Hurricane, UT
Posts: 7,743
My Jeep just arrived at the dealer today. My only concern is that I got the 430 instead of the 730n.

2 months ago I bought a Chrysler 200 hardtop convertible. It has the 730n, connectivity and the auto climate control.

The connectivity, once you get it hooked up is awesome with your cellphone. I can't speak for the Jeep yet but with the top down in the car doing 75 I can hold a voice level conversation without yelling. I haven't played with the voice controls that much yet. I like the ease of use on the 730 with a couple of bitches thrown in such as not being able to use the keypad or play a movie when in drive. Its a messed up safety feature but whatever. The Nav works okay but its very few glitches made me opt for the 430n Garmin nav instead of the 730s. Other than that I don't think there is much in difference except the 730 has more graphic features but I'll know more by Monday.
Climate control, its just what it is on Auto. Just set and forget. If the ambient temp outside requires the AC to kick in to keep you at 70 it does so. No guess work for you. It makes you a little lazy but what the hell. I got the Rubi unlimited. The only concessions I made was I got the stick, and did not get smokers group. Remote start doesn't come with manual which I believe I miss living where I do in winter.
CrazyBull is offline   Quote Quick Reply
Old 10-20-2011, 12:46 AM   #65
Jeeper

WF Supporting Member
 
Reynoldsmao1's Avatar
 
Join Date: Aug 2011
Posts: 78
Quote:
Originally Posted by oilwell1415 View Post
Those that have ordered Max Tow don't have it on their build sheets. I'll have to wait until next summer to see how the Jeep handles the boat, but I'm sketical that it will be any different than towing it with my truck. We'll see.
I ordered the Max Tow package and trailer sway is listed on the build sheet for what its worth.
"BNTP Trailer Sway Damping"
__________________
2012 JKU Bright White S-Package
6-SPD, 3.73, LSD, Max Tow, Connectivity, Hard Top
Reynoldsmao1 is offline   Quote Quick Reply
Old 10-20-2011, 04:56 AM   #66
Jeeper
 
cu in oz's Avatar
 
Join Date: Aug 2011
Location: South Coast of Massachusetts
Posts: 620
THAT old video was GREAT!!!! Thanks for posting.
__________________
'11 Sahara Tan Sport "S" H/T 6spd
cu in oz is offline   Quote Quick Reply
Old 10-20-2011, 05:10 AM   #67
Jeeper
 
SRPs 2012's Avatar
 
Join Date: Apr 2011
Posts: 88
Just tired of the leaming issues. Taking jeep back to the dealer for the 5th time today! Time for lemon law research!
__________________
2011 JK 6-Speed Detonator Yellow!
SRPs 2012 is offline   Quote Quick Reply
Old 10-20-2011, 06:34 AM   #68
Jeeper
 
filipinocracker's Avatar
 
Join Date: Aug 2011
Location: Gaithersburg, MD
Posts: 151
I should know by Friday if I regret getting my 2011 Unlimited Sport. Purchased in August 28th and itís currently at the dealership for the fourth time to fix the water leak issue. Supposedly the Sales Manager is calling Chrysler to request for a hardtop to replace my soft top. The third attempt was just a reseal so that equals to they have no idea how to fix it. Regardless of whether I get a hardtop or not this is the last attempt. A fifth visit will result in me either getting a replacement or a attorney.
filipinocracker is offline   Quote Quick Reply
Old 10-20-2011, 08:08 AM   #69
Jeeper
 
Join Date: Jul 2011
Location: Broken Arrow, OK
Posts: 2,305
Quote:
Originally Posted by recreate.me View Post
Rooster: Are you saying GET the 7 speaker sound system if you can live without the trunk space? or DO NOT get the 7 sub because its not worth the price based on sound quality ?
I got the Infiniti and am happy that I did. It doesn't take up that much room in the back. So far everything I've wanted to put back there has fit back there. Many say it sounds terrible, but that has not been my experience. It did need a lot of adjustment of the stereo settings to sound good. I don't know why the neutral settings are so far out of whack.

Quote:
I have been reading a lot about LSD, what benefits would that have over not getting LSD?
Do you want one wheel to push you forward or two? That is the difference. With the brake lock system the LSD isn't as much of a benefit as it would be, but the LSD is proactive and the BLD is reactive. I would rather not lose traction in the first place, so the LSD wins for me every time.

Quote:
and 3.21 is better for gas milage on a 2dr daily driver, no towing ?
I doubt there is any difference in mileage. For $50 the 3.73s are a better value than any other option on the list.

Quote:
Originally Posted by cu in oz View Post
The 3.21's are great for a DD/light off road use and your milage will be in the low 20's. I'm back all around just about 20.4 mpg. I also have a light foot....just saying. At 62mph (100K) I'm turning about 1750 rpms...just guessing, could be 1800, but no higher. I usually run highway at this speed in the JEEP. Now the Volvo is another matter
That's about what we get with 3.73s and 33" tires when we go that speed. We're more often at about 70 mph and it gets mid 19s.

Quote:
Originally Posted by Reynoldsmao1 View Post
I ordered the Max Tow package and trailer sway is listed on the build sheet for what its worth.
"BNTP Trailer Sway Damping"
I guess we need to add this to the list of FUBARs for the 2012 model year. Some have it, others don't. Still not worth it to me just to get another electronic nanny to watch over me. Assuming of course that it actually does anything above and beyond the normal ESC functions.
__________________
2012 Silver Sport S, Silver, 6 speed, soft top, 3.73s, LSD, PCG, Infiniti, deep tint windows, Pro Comp 1028 wheels, 33" Duratracs, Smittybilt bumpers and steps, KC fog lights, Mopar slush mats and fuel door.

Happiness is a belt fed weapon.
oilwell1415 is offline   Quote Quick Reply
Old 10-20-2011, 08:21 AM   #70
rotaredoM

WF Supporting Member
::WF Moderator::
 
panthermark's Avatar
 
Join Date: Aug 2011
Location: Chicago-land
Posts: 9,748
Images: 13
All I can do is go by the mileage thread, and in stock format, the 3.21's seem to be doing better than the other ratios at highway speeds overall. There seems to be more variance in with the 3.73's...but that could be from people testing the better response. So I'll sit back and wait for more posts to roll in.
panthermark is offline   Quote Quick Reply
Old 10-20-2011, 08:42 AM   #71
Jeeper
 
Join Date: Jul 2011
Location: Broken Arrow, OK
Posts: 2,305
I haven't visited that thread in a while. I didn't find enough consistency in the results at that time to consider them reliable. Some were just telling what the display told them, others were doing a hand calculation, and I know in stock form my speedometer/odometer was so far off the numbers would have been wrong anyway. Most of them were within 1 or 2 mpg and that is well within the range of possible error.
__________________
2012 Silver Sport S, Silver, 6 speed, soft top, 3.73s, LSD, PCG, Infiniti, deep tint windows, Pro Comp 1028 wheels, 33" Duratracs, Smittybilt bumpers and steps, KC fog lights, Mopar slush mats and fuel door.

Happiness is a belt fed weapon.
oilwell1415 is offline   Quote Quick Reply
Old 10-20-2011, 08:44 AM   #72
Jeeper
 
ShoreWrangler's Avatar
 
Join Date: Sep 2011
Location: Maryland's Eastern Shore
Posts: 941
3.21 has to get the best mileage just based on rpm's. the lower the rpm's at highway speed, the better the mileage. This would be the highway cruising mileage.

City mileage may not be much difference. How someone drives will play much more of a role in start/stop situations than the gear ratios. But at 6th gear, steady highway speed, lower rpm's = higher mileage. I don't see any way of disputing that.
ShoreWrangler is offline   Quote Quick Reply
Old 10-20-2011, 08:49 AM   #73
Jeeper
 
ShoreWrangler's Avatar
 
Join Date: Sep 2011
Location: Maryland's Eastern Shore
Posts: 941
The bigger factor with mileage is the tires. The A/T tires that come on the Sports and Sahara's should be better mileage than the off-road tires on the Rubicons. That probably hurt mileage more than the gear ratio's I imagine
ShoreWrangler is offline   Quote Quick Reply
Old 10-20-2011, 09:06 AM   #74
Jeeper
 
Join Date: Jul 2011
Location: Broken Arrow, OK
Posts: 2,305
Quote:
Originally Posted by ShoreWrangler View Post
3.21 has to get the best mileage just based on rpm's. the lower the rpm's at highway speed, the better the mileage. This would be the highway cruising mileage.

City mileage may not be much difference. How someone drives will play much more of a role in start/stop situations than the gear ratios. But at 6th gear, steady highway speed, lower rpm's = higher mileage. I don't see any way of disputing that.
Then maybe you could explain to me why the GMC truck I used to have got 12 mpg with 2.73 gears and 18 mpg with 3.08s? RPM is not the sole factor in mileage. It has just as much to do with how hard the engine has to work at that rpm to go down the road. Neither the 3.8 or 3.6 have any low end torque. That means that you will often find yourself driving with your foot on the floor in high gear just to maintain speed. At a higher rpm where there is more torque available you may be able to do the same thing with only half throttle. This is why the guys that go to 5.13 gears with bigger tires get better mileage than they did with stock gears.
__________________
2012 Silver Sport S, Silver, 6 speed, soft top, 3.73s, LSD, PCG, Infiniti, deep tint windows, Pro Comp 1028 wheels, 33" Duratracs, Smittybilt bumpers and steps, KC fog lights, Mopar slush mats and fuel door.

Happiness is a belt fed weapon.
oilwell1415 is offline   Quote Quick Reply
Old 10-20-2011, 09:08 AM   #75
Jeeper
 
JIMBOX's Avatar
 
Join Date: Nov 2009
Posts: 9,914
Of all the mods I've made to my '08 JKUR and everything she came with--

I've got ONE little REGRET, I kinda/almost/maybe/shoulda/perhaps--coulda ordered the DUAL top-

My jeeps been in the Nevada desert for over two years now and there have been times I coulda used the soft-top, might consider one after this coming winter-

JIMBO
__________________
"ya gotta have class"
JIMBOX is offline   Quote Quick Reply
Old 10-20-2011, 09:20 AM   #76
rotaredoM

WF Supporting Member
::WF Moderator::
 
panthermark's Avatar
 
Join Date: Aug 2011
Location: Chicago-land
Posts: 9,748
Images: 13
There are so many factors involved...it is hard to give good advice.

If you live in a really hilly area, I could easily see 3.73's getting better highway fuel economy than 3.21's...all other things being equal.

Or if you don't do much highway driving in the 71-72mph range....there probably isn't a reason to get 3.21's. Of course, none of it really matters with a stick because you can choose your own shift points.....but I do think the 5 speed auto gives the driver a bit more control with a much shorter 1st gear, and the ability to ride in a lower gear when ever you want.

I think the problem with the 3.21's is that it limits your ability to mod. Not a problem for me since I'm not a wheeler and I plan on staying stock...but I could see that being a deal breaker for most others.

For me....I look at it like this... I'd only go with 35's, winch, bumpers, ect if I was going to wheel. And if I were going to wheel that serious with 35's, I would want a Dana 44 axle up front and at least 4.10's anyway. So in my particular case, having the more versatile 3.73's won't do me much good. But for others, they probably make more sense (33's and very light mods).
It really depends on the individual.
panthermark is offline   Quote Quick Reply
Old 10-20-2011, 09:22 AM   #77
Jeeper
 
bigbendhiker's Avatar
 
Join Date: Oct 2011
Location: North Texas
Posts: 19
Quote:
Originally Posted by panthermark View Post
All I can do is go by the mileage thread, and in stock format, the 3.21's seem to be doing better than the other ratios at highway speeds overall. There seems to be more variance in with the 3.73's...but that could be from people testing the better response. So I'll sit back and wait for more posts to roll in.
The mileage part of this response may very well be true, but while I was waiting for my dealer to get my Jeep, they loaned me a 6spd with 3.21 gears. I had it for 4 days and driving it to work on a toll road that I have to take it would not hold 70 mph in 6th gear when ascending an overpass. For me that's not worth any possible mileage savings. I would spend the $50 for the 3.73 gears. Mine is an automatic with the 3.73 and it doesn't down shift on the same drive and will hold 70 mph.
Now with the 2012 and the 3.6 it maybe a moot point. I can't speak to that.
__________________
2011 Jeep Wrangler Sport
Deep Cherry Red
Automatic, A/C, Hardtop, and Satelite Radio
Not much else yet.
bigbendhiker is offline   Quote Quick Reply
Old 10-20-2011, 09:28 AM   #78
rotaredoM

WF Supporting Member
::WF Moderator::
 
panthermark's Avatar
 
Join Date: Aug 2011
Location: Chicago-land
Posts: 9,748
Images: 13
Quote:
Originally Posted by bigbendhiker View Post
The mileage part of this response may very well be true, but while I was waiting for my dealer to get my Jeep, they loaned me a 6spd with 3.21 gears. I had it for 4 days and driving it to work on a toll road that I have to take it would not hold 70 mph in 6th gear when ascending an overpass. For me that's not worth any possible mileage savings. I would spend the $50 for the 3.73 gears. Mine is an automatic with the 3.73 and it doesn't down shift on the same drive and will hold 70 mph.
Now with the 2012 and the 3.6 it maybe a moot point. I can't speak to that.
Yeah...it is almost impossible to make the comparisons between the 2011 and 2012's because of the different engine and tranny's.

A 2012 with 3.21's and a 5 speed auto is actually geared shorter than your 2011 with 3.73's and 4 speed auto. At 70 mph, the 2012 with 3.21's will turn about 70 more RPM's than the 2011 with 3.73's....but again...this is only for the auto's.
panthermark is offline   Quote Quick Reply
Old 10-20-2011, 09:32 AM   #79
Jeeper
 
Join Date: Sep 2011
Posts: 21
I've had mine a little over a week (2011 JKU Sport Cosmos Blue) and I love it. I dont know why I waited so long. Do get the electric windows and the connectivity package its worth it.
BANZAIKEV is offline   Quote Quick Reply
Old 10-20-2011, 09:39 AM   #80
Jeeper

WF Supporting Member
 
ShaneDiddy's Avatar
 
Join Date: Feb 2010
Location: Alamogordo
Posts: 222
Dont have the jeep just yet so I might change but only thing is Not really a regret...ill prob eventually get a soft top for it....and I really always wanted the half doors but didnt want to give up the power grp....guess ill eventually get those after market too just wish I could get the factory paint job already on them haha
__________________
2012 Deep Cherry Red Sport 2Dr 6-speed 3.73, Tow Pkg, Power Grp, Connectivity Grp, Hard Top, Deep Tint - (reordered 9/20 for Gears)
D1 Status 9/23
Built Pending Inspection 10/5
Delivered 10/24

2010 Bright Silver JKU - Sold
ShaneDiddy is offline   Quote Quick Reply
Old 10-20-2011, 09:56 AM   #81
Jeeper
 
ShoreWrangler's Avatar
 
Join Date: Sep 2011
Location: Maryland's Eastern Shore
Posts: 941
Quote:
Originally Posted by oilwell1415 View Post
Then maybe you could explain to me why the GMC truck I used to have got 12 mpg with 2.73 gears and 18 mpg with 3.08s? RPM is not the sole factor in mileage. It has just as much to do with how hard the engine has to work at that rpm to go down the road. Neither the 3.8 or 3.6 have any low end torque. That means that you will often find yourself driving with your foot on the floor in high gear just to maintain speed. At a higher rpm where there is more torque available you may be able to do the same thing with only half throttle. This is why the guys that go to 5.13 gears with bigger tires get better mileage than they did with stock gears.
I don't disagree with you and there are a ton of other factors that effect fuel mileage. In my post I said "at steady highway speed" a 3.21 should get better mileage than a 3.73 based on the lower rpm's. This assumes steady 65 mph speed, nice smooth higway, no hills. In that case the "work" should be minimal and the reduction in rpm's should produce higher mileage.
ShoreWrangler is offline   Quote Quick Reply
Old 10-20-2011, 10:05 AM   #82
Jeeper
 
JIMBOX's Avatar
 
Join Date: Nov 2009
Posts: 9,914
Just like you say-Lotta variables and


Quote:
Originally Posted by ShoreWrangler View Post
I don't disagree with you and there are a ton of other factors that effect fuel mileage. In my post I said "at steady highway speed" a 3.21 should get better mileage than a 3.73 based on the lower rpm's. This assumes steady 65 mph speed, nice smooth higway, no hills. In that case the "work" should be minimal and the reduction in rpm's should produce higher mileage.
The main variable is the engine involved and it's Efficiency rpm-

The 3.8L isn't unique, but-

The little v6 is happy/efficient at 2200 to 2800 rpm-and that doen't matter what you've done to the rest of the jeep !!

Thats why my 5.38 gears can get such high mileage-when driven sensibly !!

Smokemifyougotem

JIMBO
__________________
"ya gotta have class"
JIMBOX is offline   Quote Quick Reply
Old 10-20-2011, 01:01 PM   #83
Jeeper
 
Join Date: Jul 2011
Location: Broken Arrow, OK
Posts: 2,305
Quote:
Originally Posted by ShoreWrangler View Post
I don't disagree with you and there are a ton of other factors that effect fuel mileage. In my post I said "at steady highway speed" a 3.21 should get better mileage than a 3.73 based on the lower rpm's. This assumes steady 65 mph speed, nice smooth higway, no hills. In that case the "work" should be minimal and the reduction in rpm's should produce higher mileage.
Even in that scenario the biggest things that impact mileage are wind resistance and engine efficiency. A 16% increase in rpm that puts the engine in a place that it's 20% more efficient is a good tradeoff.
__________________
2012 Silver Sport S, Silver, 6 speed, soft top, 3.73s, LSD, PCG, Infiniti, deep tint windows, Pro Comp 1028 wheels, 33" Duratracs, Smittybilt bumpers and steps, KC fog lights, Mopar slush mats and fuel door.

Happiness is a belt fed weapon.
oilwell1415 is offline   Quote Quick Reply
Old 10-20-2011, 01:30 PM   #84
Jeeper
 
m0wens's Avatar
 
Join Date: Sep 2011
Posts: 132
I have a 2012 JKU Rubicon. No regrets here. I got everything that I requested and really enjoy driving the heck out of her.
__________________
2012 Jeep Wrangler Unlimited 4x4 Rubicon
Black | Remote Start | Connectivity Group | Max Tow|
3pc Freedom Hardtop | 5sp Auto | 4:10
m0wens is offline   Quote Quick Reply
Old 10-20-2011, 03:26 PM   #85
Jeeper
 
Join Date: Aug 2011
Location: Chicago area
Posts: 443
As Oilwell indicated, just lowering rpm does not automatically yield better fuel economy; it's more complex than that. If you run an engine at too low an rpm for its design, it won't run as efficient and you also strain the engine by slowing down the oil and coolant flow which are directly linked to the engine's rpm.

An engine is at it's most efficient power output (power/fuel-used) at the peak torque rpm. The peak torque rpm is where an engine is at its most volumetric efficient state due to its valve timing and intake/exhaust tuning; at peak volumetric efficiency, the engine is taking in the maximum fuel/air mixture during the intake stroke yielding the maximum pressure output to the crankshaft during combustion at that particular rpm. Why not just run at peak-torque-rpm all the time then? Because there are friction and reciprocating mass affects inside the engine that hurt fuel economy not to mention the added wear and tear on those internal engine components from running at a higher rpm. So, a balance is struck but there are practical limits.

With modern variable valve timing, 90% of the Pentastar's peak torque can be had at 1800 rpm, making enough horsepower for you to cruise efficiently at 1800 rpm rather than at the torque-peak 4300rpm. There is a major drop off of torque below 1800 rpm, so lowering rpm further for cruising yields no benefit. If the torque peaked at 1500 rpm, then you'd get the best fuel economy cruising at 1500rpm if there was enough torque/horsepower to cruise, but there would be little horsepower at the (necessary) higher rpms to pass/climb/tow. There isn't enough adjustment available in a normally aspirated engine to design a peak torque so low and still make generate usable horsepower at higher rpms without going to a much larger, heavy engine or turbocharging.

A turbo changes this discussion dramatically but Jeep doesn't have one yet. So the "struck balance" I mentioned earlier is the broad torque range that enables a flexible powerband to cover most aspects of driving. Since horsepower is calculated from torque applied at a given rpm, that technology has enabled rpm to be lowered enough for fuel-efficient cruising yet still provide enough torque higher up the rpm range when needing horsepower to pass/climb/tow. Even the 5.7 Hemi has evolved to this practical design application.
__________________
There are many whose education has exceeded their ability to comprehend.
BManz is offline   Quote Quick Reply
Old 10-20-2011, 03:56 PM   #86
rotaredoM

WF Supporting Member
::WF Moderator::
 
panthermark's Avatar
 
Join Date: Aug 2011
Location: Chicago-land
Posts: 9,748
Images: 13
Quote:
Originally Posted by BManz View Post
As Oilwell indicated, just lowering rpm does not automatically yield better fuel economy; it's more complex than that. If you run an engine at too low an rpm for its design, it won't run as efficient and you also strain the engine by slowing down the oil and coolant flow which are directly linked to the engine's rpm.

An engine is at it's most efficient power output (power/fuel-used) at the peak torque rpm. The peak torque rpm is where an engine is at its most volumetric efficient state due to its valve timing and intake/exhaust tuning; at peak volumetric efficiency, the engine is taking in the maximum fuel/air mixture during the intake stroke yielding the maximum pressure output to the crankshaft during combustion at that particular rpm. Why not just run at peak-torque-rpm all the time then? Because there are friction and reciprocating mass affects inside the engine that hurt fuel economy not to mention the added wear and tear on those internal engine components from running at a higher rpm. So, a balance is struck but there are practical limits.

With modern variable valve timing, 90% of the Pentastar's peak torque can be had at 1800 rpm, making enough horsepower for you to cruise efficiently at 1800 rpm rather than at the torque-peak 4300rpm. There is a major drop off of torque below 1800 rpm, so lowering rpm further for cruising yields no benefit. If the torque peaked at 1500 rpm, then you'd get the best fuel economy cruising at 1500rpm if there was enough torque/horsepower to cruise, but there would be little horsepower at the (necessary) higher rpms to pass/climb/tow. There isn't enough adjustment available in a normally aspirated engine to design a peak torque so low and still make generate usable horsepower at higher rpms without going to a much larger, heavy engine or turbocharging.

A turbo changes this discussion dramatically but Jeep doesn't have one yet. So the "struck balance" I mentioned earlier is the broad torque range that enables a flexible powerband to cover most aspects of driving. Since horsepower is calculated from torque applied at a given rpm, that technology has enabled rpm to be lowered enough for fuel-efficient cruising yet still provide enough torque higher up the rpm range when needing horsepower to pass/climb/tow. Even the 5.7 Hemi has evolved to this practical design application.
You have stated this far more scientifically than I could ever hope to dream of. When I look at the numbers (on paper), I see the 3.21's on stock wheels and 5 speed auto turning 1815 RPM's at 65mph. That is basically right when the engine hits +90% level of its peak torque (at the flywheel anyway). So on "paper" that is perfect for a non-modded daily driver on the highway. But I'm still waiting on more info to come on in terms of "real world" use.....wind, hills, cargo, parasitic loss, ect.... On the highway, I can always shift down, but I can never shift up.
panthermark is offline   Quote Quick Reply
Old 10-20-2011, 04:01 PM   #87
Jeeper
 
Join Date: Jul 2011
Location: Broken Arrow, OK
Posts: 2,305
To expand slightly on what BManz said, in addition to being at peak torque the engine also likes to be at WOT. Any time the throttle is not wide open you lose efficiency to pumping losses. This is part of the reason we get such good mileage out of small engines. We can operate them near their peak torque with a lot of throttle opening and get good mileage out of them. This is where the multi displacement technology really shines. You make the engine smaller on demand so you can dump the pumping losses of the throttle body yet still operate at a power level that doesn't cause acceleration.
__________________
2012 Silver Sport S, Silver, 6 speed, soft top, 3.73s, LSD, PCG, Infiniti, deep tint windows, Pro Comp 1028 wheels, 33" Duratracs, Smittybilt bumpers and steps, KC fog lights, Mopar slush mats and fuel door.

Happiness is a belt fed weapon.
oilwell1415 is offline   Quote Quick Reply
Old 10-20-2011, 04:13 PM   #88
Jeeper
 
Smihty's Avatar
 
Join Date: Sep 2011
Posts: 52
I recently bought a 2011 2dr sport, 3.21, 6 speed. This is my first Jeep to own and I couldn't be more pleased. It's not a daily driver, so getting the manual was a must for me along with satellite radio (FM is miserable). I did replace the stock tires with a set of 265's. I really cant tell a difference from the 225's when cycling thru the gears. I will eventually do the whole lift + 35's + gear mods. But all in good time. I've go my project Jeep I've always wanted and look forward to the years ahead (hopefully with no problems....)
Smihty is offline   Quote Quick Reply
Old 10-20-2011, 08:20 PM   #89
Jeeper
 
Join Date: Jul 2011
Location: Broken Arrow, OK
Posts: 2,305
Quote:
Originally Posted by Smihty View Post
I recently bought a 2011 2dr sport, 3.21, 6 speed. This is my first Jeep to own and I couldn't be more pleased. It's not a daily driver, so getting the manual was a must for me along with satellite radio (FM is miserable). I did replace the stock tires with a set of 265's. I really cant tell a difference from the 225's when cycling thru the gears. I will eventually do the whole lift + 35's + gear mods. But all in good time. I've go my project Jeep I've always wanted and look forward to the years ahead (hopefully with no problems....)
If you're planning gears you kinda screwed yourself with 3.21s. Going from there to where you'll want to be will cost twice as much as it would have with factory 3.73s. It's not a deal breaker, but will add a lot to the cost unless you were planning on adding lockers anyway.
__________________
2012 Silver Sport S, Silver, 6 speed, soft top, 3.73s, LSD, PCG, Infiniti, deep tint windows, Pro Comp 1028 wheels, 33" Duratracs, Smittybilt bumpers and steps, KC fog lights, Mopar slush mats and fuel door.

Happiness is a belt fed weapon.
oilwell1415 is offline   Quote Quick Reply
Old 10-20-2011, 09:18 PM   #90
Jeeper
 
Rooster76's Avatar
 
Join Date: Oct 2011
Location: Indy
Posts: 817
Gear Ratio Considerations

Quote:
Originally Posted by oilwell1415 View Post
If you're planning gears you kinda screwed yourself with 3.21s. Going from there to where you'll want to be will cost twice as much as it would have with factory 3.73s. It's not a deal breaker, but will add a lot to the cost unless you were planning on adding lockers anyway.
I would have gone with the 3.73 gear ratio personally if it was an option. They are pretty hard to find unless you order them. If he is going to get 35's he is going to need to re-gear. Even people with the 2011 rubi 4.10's and manuals are saying that 35's are a bit sluggish. From what I have read 33's are about as big as you want to go with 3.73. That being said I speak only from LOTS of research and not personal experience.

Rooster76 is offline   Quote Quick Reply
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Jeep Wrangler Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
33's on a 6 cyl TJ auto with D35 & 3.73 regrets?? mattyd TJ General Discussion Forum 5 10-15-2010 12:08 PM
No regrets! (yet) bentol888 WF New Member Check In 15 04-17-2010 07:49 AM
any regrets with your color choice tangofoxtrot JK General Discussion Forum 23 01-31-2010 09:27 PM
No Regrets Levinoss Off-Topic 34 11-02-2007 10:38 PM



» Featured Product

All times are GMT -5. The time now is 02:17 AM.



Jeepģ, Wrangler, Liberty, Wagoneer, Cherokee, and Grand Cherokee are copyrighted and trademarked to Chrysler Motors LLC.
Wranglerforum.com is not in any way associated with the Chrysler Motors LLC