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  #1  
Old 10-19-2014, 04:53 PM
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Better mpg?

I need better mpg.. I avg 13 highway which is shit lol i have an 4.7L v8 2005.. Anything i can do?


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Old 10-20-2014, 06:08 PM
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Re: Better mpg?

Things I've been told and have been doing.

Intake, TB, Exhaust, Tuner, lighter foot, and possibly look into replacing o2 sensors and plugs if you think you are having lower than normal mpg.

Just realized you said 13mpg highway...check your plugs and sensors. Clean your TB and IAC. Better airflow and a better fuel/air mix should help it some.
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Old 10-25-2014, 09:47 PM
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Re: Better mpg?

Quote:
Originally Posted by DCFD522 View Post
Things I've been told and have been doing.

Intake, TB, Exhaust, Tuner, lighter foot, and possibly look into replacing o2 sensors and plugs if you think you are having lower than normal mpg.

Just realized you said 13mpg highway...check your plugs and sensors. Clean your TB and IAC. Better airflow and a better fuel/air mix should help it some.
Most of the above. An aftermarket intake won't do that much for you, and you can modify the stock setup to be as good as any aftermarket CAI. With that poor mileage, I'd for sure be looking at the O2's, MAP Sensor, and spark plugs. The biggest weak spot on any of the WK's is the exhaust system. With my mods. (see signature), my Hemi routinely gets over 20 mpg highway....usually ~21-23, with a best of 24.4 mpg.

I just got back from a 1786.6 mile trip and overall average for the whole trip was 20.65 mpg......86.48 gallons of fuel. It would have been better if I had driven my normal 65 mph in 4th gear instead of 65-80 mph in 4th and 5th. That included almost all mountain driving, head winds, two climbs to over 6500 ft. and one to 7800 ft., and about 40 miles of city driving. Altitudes ranged from ~500-7800 ft. elevation. I use 91 fuel at lower altitudes and climbing, and 85-87 at higher altitudes. I find that using Standard/Chevron fuel works the best and if I can't get it, I add about 6-8 oz. of Techron. The very best fuel I've found is a Commerical Fueling Network (CFN) station in Wells, Nevada. It's a "no name" fuel, but all of my best mileage has come from the same pumps at this station. I use their 85 fuel, as the elevation there is 5500+ ft.

The bottom line goal to improving fuel economy is to improve the Volumetric Efficiency (VE) of the engine, without going too far overboard. IMO, your first order of business (aside from making sure all engine tune items are working properly) is to fix the exhaust. Again, IMO, headers and a low restriction header back exhaust system is the most important thing you can do. I had to have my headers custom built about 3 1/2 years ago, and they've easily paid for themselves. Next, you may want to consider advancing the stock cams by about 5-10 degrees. I have advanced aftermarket cams in both my Hemi vehicles, with a 6* advance on the WK and a 10* advance on my LX. It gets 27-29 mpg highway with about the same mods. as the WK. A Superchips Tuner with the Advanced Transmission Tuning Application (ATT) will allow you to set your shift schedules to keep your engine RPM in a range that is closer to your torque curve. That's why I drive mine, most of the time, in 4th gear....usually 65 mph in 4th gear, ~2400 RPM. If I could up the RPM to ~2600-2700 RPM, I am sure the mileage would go up a little more. Other things you can do is to cut weight (hard to do), and try to improve the aerodynamics a little. I added an SRT body kit (drag coefficient of .39 vs. the stock Cd of .41) and lower it a little which further reduces the Cd. I also use Airtab Vortex Generators on both my vehicles. The weight of mine, loaded for travel, a full tank of gas and the wife and I in it, runs right at 5500 lbs.

Other little things you can do (after the above) that make slight differences (improvements may be slight, but cumulatively they all add up) are add an underdrive crank pulley, higher voltage coils, improved, modified stock intake (two air inlets into airbox and low restriction air filter), slightly larger throttle body, and a resistor in line with the IAT Sensor to fool the PCM into thinking intake air is cooler than it really is. I haven't done this to my WK yet, but I have an adjustable setup on my LX which may help a little. Theory is that cooler intake temp. will allow the PCM to add a little more timing advance.

A few other obvious things are front end alignment (I have mine aligned with the wife and I sitting in the vehicle), proper tire pressures (go on the high side), making sure the wear patterns encompass the full tread width. Too high pressure wears center only, too low wears outer edges only. Also, much above 65 mph your fuel economy starts tanking. If I drive 75-80 mph, I'll lose 1-2 mpg. I also use cruise control as much as possible which, along with the Superchips ATT App., maximizes the MDS "on" time of the Hemi.

Good luck, and have fun tinkering. For me, fuel economy improvement is a game. It's fun to see what works and what doesn't. My goal for the WK is a fairly consistent 24-25 mpg. I've got a few more ideas I'll have to try though.
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Old 10-26-2014, 01:59 AM
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Re: Better mpg?

Quote:
Originally Posted by jeepgcoman View Post
It gets 27-29 mpg highway
wow bro, your lx gets the same range of mpgs that my 3.7 gets. but yeah, improve your VE and tune will def help as what I did.

now the 4.7 is virtually identical to the 3.7 (save for 2 more cyl and the 3.7's hair longer stroke) so I feel I may be able to help...at least with your highway mileage.

I get on the highway, even on a bad o2, get between 25.5 to 29mpg highway. heres what I did but its not 100% streel legal. ill get into that in a second.

Intake mods:
and aftermarket intake tube in itself will not make a big difference in mpgs. however, pair it with a throttle body and its worth about .5 mpg
I also am running a ported intake manifold. this is something I had to do myself since there is no aftermarket mani on the 3.7. Airram has one for the 4.7. now I really haven't done any extensive mpg testing on it.

Exhaust:
this is where my setup becomes non street legal, but if you get the air in faster you gotta get it out faster too.
my 3.7 is running headers, my own custom made mid pipes (the not legal part) and true dual all the way back. without a doubt, the exhaust will net you the biggest improvements in mpgs and I have done extensive testing on the exhaust.

here's my numbers:
100% stock city/highway: 15-18/18-21 peak of 23 (baseline #'s)
Intake/catback: 16-18/19-22 peak of 24
Intake/tb/headers/catback: 15-18/20-25 peak of 26
^^ +mani/^^+ decatt: 14-17/22-26 peak of 28 (o2 starting to go)
^^ + hypertec tune: 14-16/24-27 peak of 29
^^+ true duals: 11.5-15/25.5-29 peak of 34 (o2 completely bad)

My numbers are listed as a range because of winter vs summer and different terrain. my numbers are lower in the winter and going thru hills. best numbers are @60mph on relatively flat ground and turning 1800rpms (I have a 3.07 axle ratio) but as you can see, my city mileage also started dropping as the o2 went bad but oddly enough, my highway mileage seems unaffected by it. (right front o2 is bad)
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Old 10-27-2014, 10:10 AM
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Re: Better mpg?

I found that by using the recommended mid grade fuel instead of regular that I picked up an additional 1.5 miles per gallon on my hemi. The additional cost was off set by the increase in mileage. The recommendations are there for a reason. I've run in to too many people running regular in their hemi's and complaining about mileage.

Just my $.02 worth.
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Old 10-27-2014, 01:47 PM
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Re: Better mpg?

Jeff, the thing that made the biggest difference in mileage and performance on the LX was the 10* advanced Sidewinder cam. I've gotten a little over 30 mpg before on it, but most of my driving is at altitudes of 3000 ft. and above. That's also why I can get away with running 85/87 fuels. I also continuously monitor Knock Retard so I know if the fuel octane is wrong for the driving conditions. My WK is modded almost exactly like the LX, and I do the same with it. The LX is about 500-600 lbs. lighter and has a drag coefficient of .35 vs. the WK's (with the SRT body kit) .39. Gearing and the 4WD drivetrain load also makes a little difference in fuel economy.

Your mileage increase with the headers is even a little better than mine were when I added the headers. I think I've said before, I'd really like to "tinker" with a 3.7 like you're doing, just to see much I could get out of it. Headers/catbacks and cam(s) make the biggest difference though.
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Old 10-28-2014, 07:29 AM
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Quote:
Originally Posted by jeepgcoman View Post
Jeff, the thing that made the biggest difference in mileage and performance on the LX was the 10* advanced Sidewinder cam. I've gotten a little over 30 mpg before on it, but most of my driving is at altitudes of 3000 ft. and above. That's also why I can get away with running 85/87 fuels. I also continuously monitor Knock Retard so I know if the fuel octane is wrong for the driving conditions. My WK is modded almost exactly like the LX, and I do the same with it. The LX is about 500-600 lbs. lighter and has a drag coefficient of .35 vs. the WK's (with the SRT body kit) .39. Gearing and the 4WD drivetrain load also makes a little difference in fuel economy.

Your mileage increase with the headers is even a little better than mine were when I added the headers. I think I've said before, I'd really like to "tinker" with a 3.7 like you're doing, just to see much I could get out of it. Headers/catbacks and cam(s) make the biggest difference though.
I really need to get home and take a more indebth look at my cams. Last time i looked at them, right cam specifically, the cam tone ring and sprocket are aligned with a key on the cam itself. I really want to advance them but if they are locked like i think they are then i cant do it. Now if there is no key, i can rotate the cam separately on each head so i can shift the powerband to a little lower rpm
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Old 10-28-2014, 04:38 PM
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Re: Better mpg?

I am not familiar with the 3.7 but it shouldn't be a problem. The tone ring on the 5.7 is part of the gear too. Just count the teeth on the cam gears and divide by 360 to see how many degrees advancing one tooth will be....probably ~5-10 degrees. On the Hemi gear it is just under 7*. You'll be moving the whole gear/cam assemblies.
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Old 10-29-2014, 01:35 AM
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Quote:
Originally Posted by jeepgcoman View Post
I am not familiar with the 3.7 but it shouldn't be a problem. The tone ring on the 5.7 is part of the gear too. Just count the teeth on the cam gears and divide by 360 to see how many degrees advancing one tooth will be....probably ~5-10 degrees. On the Hemi gear it is just under 7*. You'll be moving the whole gear/cam assemblies.
Ill have to look again. But im moving 2 cams
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Old 10-29-2014, 07:56 PM
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Re: Better mpg?

I don't think that should be a problem. Just move them both ahead by one tooth. I am sure it'll be a little more work though. Just be sure to mark everything and make sure you keep the chain from coming off the crank pulley.....maybe wire it so it can't move, or ???
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Old 11-01-2014, 11:46 PM
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Quote:
Originally Posted by jeepgcoman View Post
I don't think that should be a problem. Just move them both ahead by one tooth. I am sure it'll be a little more work though. Just be sure to mark everything and make sure you keep the chain from coming off the crank pulley.....maybe wire it so it can't move, or ???
Worse case ill just pull the timing cover off. I have 3 chains
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Old 11-10-2014, 03:36 PM
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Re: Better mpg?

I recently flushed my radiator and my mpg jumped from ~17 to ~21. Same year and engine


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