Engine Designed for Long Distance

[Darky]

I'll be doing a rebuild on mine soon because I know it needs it...light knock and 12 mpg tops.

 

[DaveNJeep]

Quote -

" have over 100K on my stroker and I went from 15mpg to 21mpg on the highway, lifted on 35's "

Sorry but the noise you hear in the background is the BS alarm going off!

Lifted = MORE drag = MORE fuel
35's = MORE rolling resistance = MORE fuel
Stroker = MORE fuel

STOCK Cherokees were only rated for 21 Hwy brand new. Would you like to see my window sticker? I still have it.

But you're telling me a bigger motor, much bigger tires, and lifted to clear those tires equals THE SAME MPG? BS. And please, take those tired cliche's about more power requiring less throttle and put them in your tailpipe. By using this logic a top fuel dragster gets 21 mpg too? No.

I've owned many Jeeps in the last twenty + years, everything from XJ's, a TJ, a ZJ, a WJ, and my kids own a TJ and a JK. Know which one got the best fuel economy out of all of them? The stock WJ with the 4.0.

 

[DaveNJeep]

Maybe I was a little harsh in that last post?

Boil it down to this. If you could take the neccessary steps to fit 35's under a stock height XJ, put any gears in it you want, you're saying your mpg would INCREASE? Of course not! Now add a bigger motor, still stock height, and your getting better mpg? So at this point you've got; more rolling resistance, an engine that requires more fuel, and now you want me to believe on top of all of this, let's put more wind resistance on it by lifting it. AND YOUR MPG GOES UP?

Maybe your right? That would explain why the automotive industry is downsizing their engines, trying everything they can to lighten their vehicles, decrease drag by going to extremes like flush mount door handles, and spending hundreds of millions of dollars on R & D while all they had to do was talk to a XJ'er with 35's? Shazam!

 

[GreenMachine1]

Calm down a little bit DaveNJeep. I don't own an XJ with a stoker on 35s but I do understand some of the logic that is presented here. From my personal experience, I own a stock WJ with a 4.0 and a stock WJ with a 4.7. Based on what you are trying to say here, you must assume the 6cyl WJ gets better mileage since the v8 is a bigger motor=more fuel, correct? Well, you're wrong. The 4.0 is a bit underpowered in the big ass WJ requiring more fuel to get it moving. The V8 requires less pedal to keep it going because the motor isn't underpowered. You can directly correlate this to the stock 4.0 vs. stroker argument. Now do you understand how a stroker can potentially get better mileage than a stoke 4.0? I know I do.

 

[tom11919]

I don't have solid numbers yet, but since swapping in a set of Neon/703 injectors last week, I seem to be getting slightly better mpg. I reset the trip odo at every fill-up and am usually lucky to see 220 miles per tank with mixed highway and city driving. I have yet to burn a full tank since the swap, but yesterday I had gone 170 miles on half of a tank (on the gauge) and showed 140ish Dist to Empty on the overhead display. Those are all indicated numbers, btw. My speedometer reads about 5% fast due to 31s and 4.10s. I'm getting ready to drive 4000+ miles in a couple weeks, so real data will be forthcoming. aperwork

Moral of the story is that you have to take the long view. How long will it take for that investment in a stroker vs a stock rebuild to pay for itself through better mpg. I've got about $50 in injectors from the PullaPart and if I see a 1% increase in economy they'll have paid for themselves on this next trip.

For what its worth, I once did the math on swapping a small diesel into an XJ and figured it would take something like ten years to break even. YMMV

 

[Milford Cubicle II]

My DD 90 XJ gets a solid 16 in town and 21 highway. I'm geared 4.10 on 30's, run the Spectre cowl intake, other than that it is stock.

I'm calling :bs: on that highway number, unless you're calling "highway" 55 mph. At 70, there's no way you're getting 21mpg with 30's and 4.10's. No way.

Well, you're wrong. The 4.0 is a bit underpowered in the big ass WJ requiring more fuel to get it moving. The V8 requires less pedal to keep it going because the motor isn't underpowered. You can directly correlate this to the stock 4.0 vs. stroker argument. Now do you understand how a stroker can potentially get better mileage than a stoke 4.0? I know I do.

That argument isn't valid in an XJ application because an XJ is far from underpowered with the 4.0.

I too have seen 4.0 WJ's get excellent mileage (like around 24mpg highway) and I suspect it has a lot to do with aerodynamics. (I know, DUUUUH, right?)

And speaking of aerodynamics, I noticed a BIG increase in mileage after removing my roof rack and adding an extended lower air dam/valence. I think the air dam made the majority of the difference. And I haven't mentioned this until now cause the OP was interested in motor modifications.

 

[FlexdXJ]

I'm calling :bs: on that highway number, unless you're calling "highway" 55 mph. At 70, there's no way you're getting 21mpg with 30's and 4.10's. No way.

I can pull 20 on the highway in my 97 on 32's with stock gears. 18-19 at 70 mph. Its possible. Call all the BS you want but my scangauge is as close to hand calculated as I can calibrate it. YOu also need to take gearing into account and not just aerodynamics. If the gearing is numerically higher it takes less force to push the Jeep through the wind. I'm gonna listen to the guys who know what they are talking about saying they get in the 20's on big ass tires with gears and a stroker.

 

[Milford Cubicle II]

I can pull 20 on the highway in my 97 on 32's with stock gears. 18-19 at 70 mph. Its possible. Call all the BS you want but my scangauge is as close to hand calculated as I can calibrate it. YOu also need to take gearing into account and not just aerodynamics. If the gearing is numerically higher it takes less force to push the Jeep through the wind. I'm gonna listen to the guys who know what they are talking about saying they get in the 20's on big ass tires with gears and a stroker.

Dude, you might want to reread the post. I don't have a problem at all believing that you get 20 on 32's with stock gears. I have a problem believing that 30's and 4.10's will get 21 mpg's on the highway.

 

[GreenMachine1]

Its pretty obvious that XJ vs WJ is like comparing apples and oranges. The point I was trying to make is more power and larger displacement don't automatically equal less fuel economy like some people are trying to claim. Like I previously stated, I don't currently own a stroker so I can't comment about their economy, however, I can understand how some claim better fuel economy with a stroker vs. stoke.

 

[Tacedaddy]

GTI motor.... great MPG and you can run on veggie oil thats my .02

 

[cal]

Dude, you might want to reread the post. I don't have a problem at all believing that you get 20 on 32's with stock gears. I have a problem believing that 30's and 4.10's will get 21 mpg's on the highway.

Maybe you actually need to drive some low geared and stroked rigs, see for yourself, and then LISTEN TO THE VOICE OF EXPERIENCE.

Many years ago I ran 4.5" lift, 32" tires, 4.56 gears and averaged 22 on the highway with my 87.

With the deeper gears you have to use less throttle, and gain economy. That's the biggest thing you get from re-gearing. Of course there has to be a point of diminishing returns on that, but 30's and 4.10's are very believable. Hell, the 4 cyl XJ's with auto's came with 28's and 4.56 from the factory, the "economy" configuration.

 

[Milford Cubicle II]

Maybe you actually need to drive some low geared and stroked rigs, see for yourself, and then LISTEN TO THE VOICE OF EXPERIENCE.

Many years ago I ran 4.5" lift, 32" tires, 4.56 gears and averaged 22 on the highway with my 87.

With the deeper gears you have to use less throttle, and gain economy. That's the biggest thing you get from re-gearing. Of course there has to be a point of diminishing returns on that, but 30's and 4.10's are very believable. Hell, the 4 cyl XJ's with auto's came with 28's and 4.56 from the factory, the "economy" configuration.

By that logic, I should be getting better mileage in 3rd rather than in 4th gear at 60 mph. And that's definitely not the case.

 

[cal]

Are you sure its not the case? Have you done a 100+ mile test on the same terrain in each, in the properly selected gear allowing the torque converter to lockup?

 

[O-Gauge Steamer]

I can say, from experience, that the mileage on the 97 I had went up after the engine was rebuilt into a 4.7.

Vehicle Specs:
97 Sport, AX15, 241OR TC, 4.11:1 gears, 32x10.50 tires and a 4.7L stroker with tuned headers, a 99+ Intake manifold (reworked), 68mm Throttle Body (from the 4.7L V8) and an aluminium big valve cylinder head.

The comparison is between pre and post engine rebuild, the rest of the rig was the same. The original engine had near 180,000 miles on it. Popped in the new engine and after the engine was broken in, my highway mileage went up by 4mpg. At the time, I was working in Aurora Colorado and had a 75 mile each way commute. Used way less throttle. On the order of running maybe 50% instead of 80% on the same stretch of Colorado Hwy 83.

Here are some well documented facts:
Large, wide heavy tires kill mileage. That's right! If you want mileage, put Pizza Cutters on it. The less contact you have, the less rolling resistance you have.

Running at WOT kills mileage. This is a fact. At WOT, the computer shifts out of closed loop and just dumps fuel into the engine to prevent detonation. It is better to downshift and run at a higher rpm with the throttle closed down.

Slow accerations save gas. Well yes, yes it does.

Shut the engine off at stop lights. I have done this since the early 60s (OK, I'm old) and it should not be a surprise that at Zero mpg, the average drops... What is interesting, to me at any rate, is that high end vehicles (BMWs come to mind) this now happens automatically. The engine shuts down and then restarts when the foot feed (you youngsters call it a "gas pedal". Some of us have driven vehicles that only had a hand throttle...) is pressed.

It is called "hypermiling".

Given a choice on an engine rebuild, it would all depend on the state of the crankshaft. If it needs to be turned or, by the same token a crank kit is to be used, then bumping up to 4.5 Litre with just enough bore to clean up the cylinders makes sense and should only cost a couple of hundred more. The 258 crank kits, on average, cost a hundred more than 4.0L kits. Look to the cam timing. Several Cam manufacturers (Crowley being one) point out the advantages of altering the valve timing on their websites. You want a cam that makes the power off idle to the mid 2k rpm range. So, large lift and long duration is out. Keep in mind that cams are replace along with the lifters. You cannot run used lifters on a new cam.

Mostly, it is keep your foot out of it. But, expecting high mileage numbers out of a vehicle that has all the aerodynamics of a brick wall is just plain silly. The XJ is heavy, underpowered and inefficient. You can increase the efficiency, but it is not cheap.

I run a supercharger and get 15 in town, around 18 on the highway. When it was perfectly stock, I got 15 in town and around 18 on the highway.

The rig is not stock. I am running P185/75R16s with 4.56 gears. WHat is getting me the mileage is not the supercharger. With theis tire/gear combination, I have a 10.2% mechanical advantage over stock. So, with the engine turning 10.2% faster, it is up on the power curve and thereby requires less throttle to operate. For those wondering just how I could possibly be sure of the mechanical advantage percentage, a -10.2% value was needed to correct the speedomoter back to stock. This means that the driveshaft is tirning faster than stock which, in turn, means advantage. Prior to the lift/tires and gear changes, I had P235R15 and the stock 3.55 gears. In order to correct the speedometer with that combination, I had to put in a +3.6% for correction. So, making the change over netted me an overall 13.8% improvement in efficiency.

Oversized tires and stock gearing means loss of efficiency. Your best bet for a high miler? Subaru. My kid gets 32mpg on the highway with his 1990 Subi Legacy and it has 248,000+ miles on it...

 

[Vanimal]

i hate people who hypermile. they XXXX up the traffic for everyone else. i lost count of how many lights i missed because some douchebag thinks it's efficent to coast up to the light from 500 feet back. When the traffic light sensor sees that big of a gap it thinks it's time to change, and it screws everyone behind this jerk. Also, when there's a left hand turning lane, don't coast up to the light preventing everyone from getting in that lane in time before the light changes. you're actually hurting the enviroment because now there's cars sitting there for several minutes idling instead of rolling through. and want to do 60-65mph on the highway? fine! but get the hell out of the passing lane, aka the fast lane. left lane loafers should be shot on sight.
I have no problem with people saving gas or money, however when the ripple effect negatively effects other people, i do have a problem, and it's a big issue here with all the lights and traffic.
not saying anyone in here does all this, i just see red when i hear the term hypermiler lol

 

[kastein]

It's cool for the motor to shut off automatically and then start back up when you push the pedal, but I don't want to sit behind some... person... who has to start their car up again by hand, especially if they miss the light because it is not one they know the timing of.

And most hypermilers are fools.

 

[Vanimal]

It's cool for the motor to shut off automatically and then start back up when you push the pedal, but I don't want to sit behind some... person... who has to start their car up again by hand, especially if they miss the light because it is not one they know the timing of.

And most hypermilers are fools.

agreed on both accounts.

 

[WebDog]

i hate people who hypermile. they XXXX up the traffic for everyone else. i lost count of how many lights i missed because some douchebag thinks it's efficent to coast up to the light from 500 feet back. When the traffic light sensor sees that big of a gap it thinks it's time to change, and it screws everyone behind this jerk. Also, when there's a left hand turning lane, don't coast up to the light preventing everyone from getting in that lane in time before the light changes. you're actually hurting the enviroment because now there's cars sitting there for several minutes idling instead of rolling through. and want to do 60-65mph on the highway? fine! but get the hell out of the passing lane, aka the fast lane. left lane loafers should be shot on sight.
I have no problem with people saving gas or money, however when the ripple effect negatively effects other people, i do have a problem, and it's a big issue here with all the lights and traffic.
not saying anyone in here does all this, i just see red when i hear the term hypermiler lol

Ha, most the time I just stay on the far right lane and pass everyone on the left... Though when I do get in the left lane and set a pace of say 70mph people do get out of my way when they look in the mirror. I think it helps having the brush guard and so many lights on the front...

 

[DaveNJeep]

For the final word on this subject -

MILLIONS of $ spent on these numbers by Companies looking for any edge they can get in this hyper-competitive market employ Engineers with YEARS of experience in this endeavor. They assembled the finest testing equipment money can buy, spared no expense to gather this data...

http://www.fueleconomy.gov/feg/Find.do?action=sbs&id=21418&id=21587&id=21419

Read. It.

But hey, you and your XJ with 35's have them outsmarted?

 

[hubs97xj]

The "final word" is that the 05 Grand Cherokee has different fuel economy estimates, depending on which engine and drivetrain it has? Well, you sure showed them.