Rolling resistance and driveline efficiency?

[PurpleCherokee]

I was wondering what, if any real "advancements" in driveline efficiency have been made in say, the last 10-15 years. XJ's have a reputation for being not so fuel efficient and that a lot of that has to do with being 4wd, solid front/rear, etc. and I was wondering if any of the new driveline designs could be used in the XJ application to maybe squeeze a little more power to the wheel and/or get a little bit more MPG's.

Driveshafts, u-joints, axles, transfer cases, tranny's, etc. which of these are more or less efficient (leading to the least amount of drivetrain loss) than other models, or types? Assuming you're on stock rubber (just to take tires out of the equation because I think we all know that a set of 38" SS's are gunna lead to more rolling resistance than a set of street tires).

Doesn't seem like this subject has been addressed much (possibly for good reason) but I'm curious.

 

[RCP Phx]

I was wondering what, if any real "advancements" in driveline efficiency have been made in say, the last 10-15 years. XJ's have a reputation for being not so fuel efficient and that a lot of that has to do with being 4wd, solid front/rear, etc. and I was wondering if any of the new driveline designs could be used in the XJ application to maybe squeeze a little more power to the wheel and/or get a little bit more MPG's.

Driveshafts, u-joints, axles, transfer cases, tranny's, etc. which of these are more or less efficient (leading to the least amount of drivetrain loss) than other models, or types? Assuming you're on stock rubber (just to take tires out of the equation because I think we all know that a set of 38" SS's are gunna lead to more rolling resistance than a set of street tires).

Doesn't seem like this subject has been addressed much (possibly for good reason) but I'm curious.

What subject?What NEW things do you know about that the rest of us dont! I get 18-22 on 32's and 15-20 on 33's!

 

[CanMan]

 

[Ba-Riedo]

Seriously? The reason that XJ's are not fuel efficient is their aerodynamics.

Listen closely...


YOU CANT MAKE A BIG ROLLING BOX FUEL EFFICIENT.



-Alex

 

[whitneyj]

When I was rolling on my stock 29er's, it wasn't unusual for me to see 24-26 mpg. I'd say that's pretty damned good for a 4x4 SUV. I'm not sure where you're getting your info from, but my buddy's 00-something blazer gets significantly less than that with "the modern IFS suspension".

 

[Kejtar]

YOU CANT MAKE A BIG ROLLING BOX FUEL EFFICIENT.

You got it wrong... it's a brick not a box

 

[igotanxj]

I would think that solid axles would be more energy effecient than independant suspension, its seems to be a lot less moving parts and leaf springs probably weigh less than a multilink setup with a crossmember. Unless you have aluminum control arms and other parts i don't see a benefit besides ride and quietness.

Overall I don't think much has really changed over the years to make the driveline more energy effecient. R&Ps are identical to what they used to be. The 08 Jags I work on have 6 speed auto transmissions, and lexus and MB have 7 speeds, but the inside of it looks just like your typical TH350. Not much has changed there except making them bigger and heavier to have more gears.

 

[besthaticouldo]

yea i think of an xj as two bix blocky legos jammed on top of each other with wheels

you want fuel efficiency buy a sub compact car...thats the best way to get it.

 

[ECKSJAY]

 

[PurpleCherokee]

I would think that solid axles would be more energy effecient than independant suspension, its seems to be a lot less moving parts and leaf springs probably weigh less than a multilink setup with a crossmember.

Ya know, I've been pondering that too and I can definately see both sides. With a solid axle, you definately have less moving parts which means less loss through friction, but you have a lot more mass which can work both ways. It can add inertia which makes it easier to maintain speed but also means that it takes more energy to accelerate. Generally, it's more efficient to have as little mass as possible unless you plan on traveling at a steady speed all the time (e.g. highway driving). So the question is in this scenario, does the lack of moving parts overcome the extra mass?

Overall I don't think much has really changed over the years to make the driveline more energy effecient.

That's kind of what I suspected but I dunno, I was hoping somebody else would :wave1:

 

[besthaticouldo]

you don't buy a cherokee for gas mileage

plain and simple

im happy when i get 16

 

[scottmcneal]

you don't buy a cherokee for gas mileage

Dam, They lied to me... :eyes:

 

[PurpleCherokee]

Seriously? The reason that XJ's are not fuel efficient is their aerodynamics.

Listen closely...


YOU CANT MAKE A BIG ROLLING BOX FUEL EFFICIENT.



-Alex

Listen closely...

AERODYNAMICS MATTER VERY LITTLE AT LOWER SPEEDS.



-Austin

Not only that, but there's a LOT more involved with XJ fuel efficiency than aerodynamics. Aerodynamics are a big factor ON THE HIGHWAY but certainly not the only factor and certainly can't be used as a blanket statement as to why XJ's don't get the best gas mileage.

 

[PurpleCherokee]

And again, this is more out of curiosity than to turn an XJ into a prius as I said before in the beginning of the thread, I'm just curious as to if it could IMPROVE the gas mileage of the XJ.

could be used in the XJ application to maybe squeeze a little more power to the wheel and/or get a little bit more MPG's

 

[igotanxj]

They'd probably get better fuel economy with a mass air system instead of speed density.

 

[besthaticouldo]

where do you get your best mileage?

cuz i sure dont get it doing 25 mph and always stopping and starting

the jeep has SO MANY THINGS WRONG WITH IT FOR OPTIMUM MILEAGE THAT YOU ARE BETTER OFF BUYING A DIFFERENT VEHICLE.

GET A CLUE

SOLID AXLES, 4X4, TERRIBLE AERODYNAMICS, TORQUE BASED MOTOR, 6 CYL, etc etc

you will get bad mileage no matter what

 

[ECKSJAY]

Obama sez to put more air in tires. Have you tried that yet?

 

[PurpleCherokee]

Good grief how many times do I have to say it?

to maybe squeeze a little more power to the wheel and/or get a little bit more MPG's

I'm not looking to get 30, or even 20 MPG!

I was wondering what, if any real "advancements" in driveline efficiency have been made in say, the last 10-15 years

and

IF any of the new driveline designs could be used in the XJ application.

A lot of people got the idea that I wanted to get great mileage just by upgrading a few driveline components to get better gas mileage and I think it's cause they didn't READ the post

What about you guys that have upgraded to D44's or D60's? Have you seen any difference in mileage? And yes, I do realize that most of you with D44's or 60's probably aren't that concerned with efficiency :wave:

 

[besthaticouldo]

i've read the posts

the answer to your question is NO.

 

[PurpleCherokee]

Obama sez to put more air in tires. Have you tried that yet?

:roflmao:

No... but I think we should all do that so we don't have to drill anymore for oil...

And judging by your first post, you're one of those who didn't read the thread

:cheers: