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Unread 11-15-2012, 06:20 PM   #301
Rockdrummer93
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2001 XJ Cherokee 
 
Join Date: May 2010
Location: Taylors, South Carolina
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Yeah that is confusing me too. I have an AW4, 4.88s and 35s and get about 2100rpm at 60mph in forth.

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Unread 11-15-2012, 06:28 PM   #302
Texsun
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Quote:
Originally Posted by mschi772 View Post
Why are you calculating distances by adding up the trips to and from work and little bits like .6 to the station when your trip meter should be more than sufficient for telling you how far you've gone since your last fillup? Or are you not doing that? I don't really follow your notes, but that's OK cuz they're your notes.

More importantly I'm a little stuck trying to figure this all out by myself because no matter how I do the math, I can't see how you cruise at 1400 rpm. You have an AW4 with 5.13 gear ratio and 35" tires, yes? My math says you should be between 2000 and 2400 RPM in 4th gear with that setup. I'm so interested because if you're really pulling-off 25 mpg (something ecomodders struggle to accomplish), then I want to figure-out what's making that possible for you because a lot of Jeepers would love to improve their mpg by 30% or more.

I am tallying up each trip to prove to you and others that my odometer is reading fairly accurate. I will post a video tomorrow morning on my way to work when I get on the highway and set cruise control at 60 MPH for now here is a video of me doing between 45-50 up a slight hill. 80% of my driving is up here in the Mountains of GA "Dahlonega, GA" If needed and to prove a point that I do not lie for E-Fame or to make my MPG seem better I can set up my GoPro and record the entire drive to work.

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Unread 11-15-2012, 07:54 PM   #303
No4x4Yet
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I don't think anyone is doubting you more so wondering how to get that same mileage. I would love to be able to pull that off myself. Gotta say though if yur trip is 80% uphill to work it's 80% downhill home.
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Unread 11-15-2012, 07:54 PM   #304
Camfam07
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haha I dont think the man has anything to lie about here honestly, I dont think he is altering his rpms and speedometer while filming and driving down the road, keep on jeeping on bro! I dont care if it was getting .0024 or 240 mpgs its a bad mofo man.
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Unread 11-15-2012, 08:36 PM   #305
mschi772
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Quote:
Originally Posted by Texsun View Post
I am tallying up each trip to prove to you and others that my odometer is reading fairly accurate.
Gotcha. I understand now.

Quote:
Originally Posted by No4x4Yet View Post
I don't think anyone is doubting you more so wondering how to get that same mileage. I would love to be able to pull that off myself. Gotta say though if yur trip is 80% uphill to work it's 80% downhill home.
Exactly. I'm not accusing you of lying for "E-fame." Honestly, I'm not entirely convinced that your results are somehow unintentionally wrong, and I'm watching and asking questions in order to eliminate the possibilities. I just want to figure-out how this is possible for the benefit of everyone who buys gas for their XJ.

You're getting so much attention because if it is legit, we want to know HOW so that we can reproduce it. Everything about your rig screams crappy gas mileage yet you seem to be getting mileage that's not just a little but a lot better. As far as I'm concerned, if I can figure-out how you've managed to get mileage like that despite all the stuff that should be killing your mileage, I can't wait to see what kind of mileage I can get with my less draggy daily driver XJ.


Quote:
Originally Posted by Rockdrummer93 View Post
Yeah that is confusing me too. I have an AW4, 4.88s and 35s and get about 2100rpm at 60mph in forth.
Yeah, 5.13 should mean even higher RPM than that.

Could someone please check my math on this? I must be missing something because every way I try to calculate this, I find it impossible for someone with a 4.0, AW4, 5.13 gearing, and 35" tires to cruise at such a low RPM (my math tells me it should be about 2400 RPM). No, I'm not accusing you (Texsun) of being dishonest, but perhaps I have the wrong info or there's something you've forgotten to mention.
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Unread 11-15-2012, 09:16 PM   #306
Texsun
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In all honesty, I am blown away with the RPM/MPG. My previous XJ had 4.56s and 35s I would be doing 2200-2500rpm doing 55-60 mph. I did mention that I installed the "flux capacitor!" on page 16 post #233


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Unread 11-15-2012, 09:39 PM   #307
1990JEEPXJ
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The only way you're turning those rpm at that speed is either your speedo is off or you don't have 5.13's

I have 4.88's and 33's and run around 2500 rpm at 65 mph. With the corrected speedo. And I only avg about 14 mpg
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Unread 11-15-2012, 09:42 PM   #308
ghrillz
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Quote:
Originally Posted by Texsun
In all honesty, I am blown away with the RPM/MPG. My previous XJ had 4.56s and 35s I would be doing 2200-2500rpm doing 55-60 mph. I did mention that I installed the "flux capacitor!" on page 16 post #233
Lmao can you come down and help me install mine? I can't get the wiring right and I keep getting negative mpg's lol
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Unread 11-15-2012, 10:36 PM   #309
Texsun
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Quote:
Originally Posted by 1990JEEPXJ View Post
The only way you're turning those rpm at that speed is either your speedo is off or you don't have 5.13's

I have 4.88's and 33's and run around 2500 rpm at 65 mph. With the corrected speedo. And I only avg about 14 mpg
I am running 5.13s, and my speedo is corrected as close as it can be "41 teeth"
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Unread 11-15-2012, 10:58 PM   #310
ScottD16
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I think it's the puppy mounted up front. I hear puppies improve gas mileage just like how stickers boost that HP.

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Unread 11-15-2012, 11:30 PM   #311
mschi772
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Quote:
Originally Posted by Texsun View Post
My previous XJ had 4.56s and 35s I would be doing 2200-2500rpm doing 55-60 mph.
That only serves to confirm that my math is right. 5.13 ratio would require more RPM than 4.56 to go the same speed. It's really hard to explain your mpg or, honestly (sorry), believe it when you're claiming a 60 mph RPM that would require something like 40+" tires and a gear ratio of like 3.3. I seriously have no interest in flaming, busting, or celebrating you. I just wanted to get the bottom of how a rig like yours could get mpg like that, but I'm just about to consider this myth busted.

When it comes to your rig in general, it's not my style at all, but I respect the hell out of it and all the work you've put into it. If only I had a fraction of the time, skill, and money you've spent on that thing... As long as it goes when the skinny pedal is pressed and stops when the fat one is pressed, I don't doubt that it will be quite fun to wheel.
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Unread 11-15-2012, 11:45 PM   #312
Texsun
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So the myth is...? My mpg expirement is still underway. My speedo is not off by much. I highly doubt my Tach is wrong, what shall we do? Once I complete this mpg and break in of the gears it will more than likely sit till after Christmas when we go to Moab.
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Unread 11-16-2012, 01:35 AM   #313
XJAbuzer
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Quote:
Originally Posted by Texsun View Post
So the myth is...? My mpg expirement is still underway. My speedo is not off by much. I highly doubt my Tach is wrong, what shall we do? Once I complete this mpg and break in of the gears it will more than likely sit till after Christmas when we go to Moab.

Do you have a smart phone? If so, download Ulysse Speedometer. I have tested it's calibration with about 6 cars that were bone stock and less than 5 years old and it was right on the money with what the car's speedometer said.

I used it to find out that my speedo is 5 miles off with 35" KM2s, 4.56's, and factory speedo gear. Average true MPG in ideal weather on flat ground is between 20 and 22 mpgs highway.

I also have some light mods done to the engine, so you can't really compare it to stock. With the Comp RV cam I have now, I rarely have to put the accelerator down farther to maintain my speed on a hill.

Since the wind factors, humidity, outside temp, etc are rarely ideal in Oklahoma, I get around 18 to 20 "true" mpg. IIRC, I am turning around 2000 or 2200 rpm at 70, can't recall which.
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Unread 11-16-2012, 06:48 AM   #314
Texsun
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20-60mph slight acceleration.

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Unread 11-16-2012, 07:17 AM   #315
mschi772
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Quote:
Originally Posted by Texsun View Post
So the myth is...? My mpg expirement is still underway. My speedo is not off by much. I highly doubt my Tach is wrong, what shall we do? Once I complete this mpg and break in of the gears it will more than likely sit till after Christmas when we go to Moab.
You claimed 1200-1300 RPM at 58 mph. The math doesn't lie--there's no way that's possible with your setup unless you're going downhill or something. Your video here just showed me about 2000 RPM at 60 mph. That's very different than 1300 RPM and quite a bit closer to the 2400 RPM at 65 mph that my math has been giving me. I'm not sure if that 5 mph difference can account for 400 RPM because I'm not about to do the "raw" math for 60 mph, so I'll give it the benefit of the doubt (you could also have a tailwind or be going downhill slightly or be drafting or some combination).

For anyone curious, I've been using various gear ratio charts to kick-start my math so that I don't have to slog through the calculations of tire circumference to speed. I've been using the figure of .75 for the fourth gear ratio of an AW4. That may not be exactly right as I've seen slightly different numbers from different sources, but it's close enough for my purposes. I've been using a rear end gear ratio of 5.13, and a tire diameter of 35 inches. A gear ratio calculator here () has been used to double-check my work using the AX15 transmission as a substitute since it's listed final ratio of .79 is close enough if the the same as an AW4's.

That was just a minor mystery to deal with while waiting for some mpg data, but initial data is suggesting that you are getting significantly improved mileage. With your permission, I might like to link to this thread over at ecomodder.com. Lots of guys there are so serious that they have some fancy computer software that might help figure-out how your rig could be getting 30% improved mileage despite, relative to a stock XJ, terrible aerodynamics, heavy parts, and large resistant contact patches.
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