Rolling resistance and driveline efficiency?

[frozen chosen]

I would love to be getting some of the MPG's you guys are talking about on here....I live in ND and everything is flat.... With 31 Dunlop mudrovers and stock 3:55 gearing I am happy when I get above 14 MPH....only seen it 1 time since I put these tires on though.... I also know that with the temps we have been having, -5* to maybe 10* F I am running rich for a longer time for the warm up of the motor....If these MPG numbers seem off please let me know so I can start looking into why I am getting this..Also 4.5 rough conutry...

 

[vetteboy]

This thread makes me sad.

Yes, there are tons of ways to make the driveline more efficient. Even disregarding the motor, which in itself is going to be the largest contributing factor.

I'd suggest you do a cost/benefit analysis before giving this thread any more serious thought.

 

[pb_beaker]

LMFAO....

 

[Mr_Random]

Sounds more like you'd rather be a mechanic than an electrician.

Took me a bit to understand what you mean... No I want an actual engineering degree, I love the theory as much as the practical work in both areas. Thermodynamics, hydrodynamics, electrical conductivity, calculations regarding stuff like that... Oh, ever do 3D binary decoding? I was the only one to pass that section of my electronic class... (In all honesty, I can't remember ANYTHING about it, just that it was fun, challenging, and mind-opening). I was the youngest in the class...

Out of seven hundred seniors, fifty took the AP calc class, about thirty of that fifty passed, and I had one of the higher grades of those thirty... I hope that says something regarding my ability to obtain a degree...

Okay okay, anyone have the specific coefficient of drag for the cherokee? I know it's much lower than that of the wrangler or anything previous to the XJ, because it has a lower hood line and curved windsheild.

 

[vetteboy]

0.51, with a frontal area of 24.5 square feet.

The TJ is 0.55 with a hardtop, the YJ was 0.63.

 

[asp]

don't forget that that's going to change once the xj is modified... removing front bumpers and replacing them with other stuff and lifting it and exposing the steering and underbody more to moving air is going to increase it. by what factor, i have no idea.

 

[MrShaft696]

i suggest you drive it around inside a vaccum that would be good

 

[srimes]

this gets back to trying to polish a piece of crap. it just can't be done.

They covered that on mythbusters and busted it. They actually polished a turd to a high level of gloss.

 

[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.

You sure have done alot of "backpeddling" from your original post!

i suggest you drive it around inside a vaccum that would be good

I think he's aready operating in one!

 

[j99xj]

The only "real" advancement in terms of efficiency are hybrid cars. I know "hybrid" is a dirty word on a site like this but it terms of science its a good concept.

It's really a shame that most hybrids are piece of sh*t cars. But there is real promise in the technology with heavy vehicles like suvs and trucks. The Cadillac Escalade and the GMC Sierras are now coming with hybrid options and getting very good results.

They are just so damned expensive its hard to justify the cost.

All a hybrid does is take most of the heat that is normally generated when braking and CAPTURE it (exactly like "dynamic brakes" on a train engine) so some of it can be reused. When a normal vehicle brakes, the pads/rotors get hot and ALL the heat/energy is lost to the surrounding air.

The problem with hybrids is that they only work well in lots of stop and go city driving and do diddly squat on the highway when you are going a steady speed.

 

[igotanxj]

They covered that on mythbusters and busted it. They actually polished a turd to a high level of gloss.

Holy crap! (pun intended) I didn't believe it so i looked it up on youtube and they definitely made shiny poop without any kind of polish or wax.
http://www.youtube.com/watch?v=hBj6PonX14A

 

[asp]

i suggest you drive it around inside a vaccum that would be good

how's the engine going to breath? :doh:

 

[PurpleCherokee]

You sure have done alot of "backpeddling" from your original post!

That WAS my original post. It's kinda hard to backpedal from the beginning. :gee:

I think he's aready operating in one!

:huh:

 

[winterbeater]

If you pull a vacuum through the exhaust, would it work like a supercharger and flow more air through the motor?assgas:

 

[PurpleCherokee]

No, I think it would just scavenge like crazy... so yea kinda lol :roflmao:

 

[asp]

If you pull a vacuum through the exhaust, would it work like a supercharger and flow more air through the motor?assgas:

no, they need at least a little bit of back pressure