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AlexG
Dodge Dakota
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4/29/2008
16:59:28
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 Subject: RE: Looking for better fuel mileage? Help.
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I took it for a test drive this past weekend, It's an automatic tranny, but I don't remeber what speed it was. But hell yeah on that 4.7L V8 rumble. My 4.0L V6 don't come close.
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NJDodge
Dodge Dakota
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4/30/2008
08:16:49
|  RE: Looking for better fuel mileage? Help.
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Just as miltonwaddums said, change your driving habits. I came over to Dakota from full size Dodge 2500's. Currently still have my hemi 4x4 with 4:10. Switching to a Dakota is like driving a car and sort of "mushy" feel. I had my injectors cleaned and it boosted the mpg's by 1.5. I also have started going easy on fast starts etc. My area is a mix of open 2 lane roads with lights and stop signs every 2-3 miles then some open highway. Now consistent 20-21 mpg. That's '05 club, auto, 4.7 4x4.
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SDave
Dodge Dakota
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4/30/2008
11:59:04
| RE: Looking for better fuel mileage? Help.
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Seriously get rid of the MSD coil. They are notorious for going bad. Go back to the stock coil. If you want you can use a MSD 6AL to boost output of your spark.
For better gas mileage try some colder plugs. Champion RC9YC or Autolite 3922's. Go with some taller tires next time you need them like 1-2 inches taller. Taller tires will change your overall effective gear ratio to a 3.21 gear ratio or something closer to that number. The lower the effective gear ratio the better the mileage you will get. Headers could definetely help if you drive conservatively afterwards. Anything that improves the effeciency of the engine should improve economy. And if you are indeed getting 19.5 at 70 mph, then you should get a couple of mpg better if you drive 55-60. With my truck I see about .5 to one mpg difference in gas mileage for every 5 mph over 55.
19.5 on the road is the best I have heard from a fullsize Ram truck with a 360, automatic, and 3.55 gears. A friend of mine has one and that is what he gets. His mods are performance muffler and K@N drop-in filter.
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TexasTodd
Dodge Dakota
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4/30/2008
13:01:10
|  RE: Looking for better fuel mileage? Help.
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Seriously get rid of the MSD coil.
Or just get an economy car!
Round Mouth
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jjj
Dodge Dakota
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5/01/2008
19:53:27
| RE: Looking for better fuel mileage? Help.
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"Go with some taller tires next time you need them like 1-2 inches taller. Taller tires will change your overall effective gear ratio to a 3.21 gear ratio or something closer to that number. The lower the effective gear ratio the better the mileage you will get."
Not nec. true, it depends on where you live and if you carry extra weight, engine package, etc.
If you live in a hilly area, a 3.21 ratio vs. 3.55 ratio may actually lose mpg.
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miltonwaddums
Dodge Dakota
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5/01/2008
21:51:47
| RE: Looking for better fuel mileage? Help.
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I tend to agree with you jjj.
Upsizing your tires will offer no performance or mileage gains except for increased ground clearance. Increasing tire diameter will increase unsprung and rotating mass. Also, a 2" gain in tire diameter will lift the truck 1". This equates to about an extra .5' of frontal area, increasing CdA. I knew this going in, but I am guilty of upsizing my tires. They look sweet though, lol. However, my mileage took a dump.
Many dakota owners report better mileage with more aggressive gears. More aggressive gears will multiply the torque output from the engine and can take load off of the motor so to speak. There's lots of theories on why this is, many claim the throttle can be opened a little further, thus allowing higher MAP and reduced pressure drops. Internal engine friction goes up however with increased engine rpm. A 3.55 to 3.92 change is only about 10% increase, so figure going from 1700 rpm(ish) to 1870 rpm(ish) at 65mph for example. This isnt that much of a change considering that most fuel goes to overcoming aerodynamic forces, etc. Not the slight increase in engine rpm. After all this dont forget about the fun factor of a 10% no b.s. increase in RWTQ.
Good Day!
Jay
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SDave
Dodge Dakota
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5/03/2008
16:05:35
| RE: Looking for better fuel mileage? Help.
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The stock tire size that came on my 94 Dakota were 205/75R/75. Which are 27.1 inches tall. I run a 235/60R/15 (26.1 inches tall) on the front and 275/60R/15 (28 inches tall) on the back. The taller tire on the back provided an additional 1 mpg increase. They are also provide a quicker elasped time in the 1/4 mile due to the larger circumferance of the 275/60R/15's. The 275/60R/15's are especially noticeable difference on the last 1/8 mile in the 1/4. They were worth a good 3 car lengths.
There may be some cases where the gas mileage goes up when you go a lower gear ratio. But it would depend mostly on the gear ratio/tire size combination used and the mods of the engine. In most cases, the gas mileage would probably go down. Maybe not so much in town, but definetely on the road.
318 engine mileage on the highway.
3.21 gears = 24-25 mpg.
3.55 gears = 22-23 mpg.
3.92 gears = 20-21 mpg.
Just my opinion opinion and what I have observed from the people and friends that drive Dodge Dakota pickups.
Having said all that I now want to try 3.92 gears with at least 28 inch tall tires to see for myself how it would perform and what gas mileage it would get.
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TexasTodd
Dodge Dakota
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5/03/2008
16:26:28
| RE: Looking for better fuel mileage? Help.
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BS ALERT, BS ALERT
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Kowalski
GenIII
5/04/2008
08:15:21
| RE: Looking for better fuel mileage? Help.
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SDave - you didn't mention what rear gear you are currently running; but comparing your earlier generation 5.2 to a 4.7 is like comparing apples to oranges. The 4.7 is higher winding, with more power up top in the revs. Many of us with the 4.7 have actually seen a slight rise in milage going to lower gears. Mine gets better milage with 4.10 than it did with 3.55.
Lead, follow, or get out of the way
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BMac
Dodge Dakota
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5/04/2008
09:45:55
| RE: Looking for better fuel mileage? Help.
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You want mpg's, build a couple H2 Generators and put them inline with a PCV filter. Clean the PCV Filter every gas fill-up and see all the crap it takes out of the system. The H2 will clean the rest of the engine inside, clean you emmisions and pick up the gas mileage.
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jjj
Dodge Dakota
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5/04/2008
10:36:26
| RE: Looking for better fuel mileage? Help.
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"The taller tire on the back provided an additional 1 mpg increase. They are also provide a quicker elasped time in the 1/4 mile due to the larger circumferance of the 275/60R/15's. The 275/60R/15's are especially noticeable difference on the last 1/8 mile in the 1/4. "
If this is the case then either you are overgeared to start with or you are low on HP on the top end.
Running taller tires will not result in a quicker et on a properly setup car - assuming you are hooking up with both sizes.
You are running small tires so that makes your effective ratio higher.
My stock tires are almost 31' tall and to be honest I think adding the 4.10's helped mileage with my 5.9 - though I haven't really tested it yet as they are fairly new.
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SDave
Dodge Dakota
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5/04/2008
16:44:14
| RE: Looking for better fuel mileage? Help.
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I am running a 3.55 gear. I can understand someone getting better mileage with the lower gears if you are driving a 4x4 dakota with large offroad tires or a fullsize Ram pickup.
That is not neccasarily true JJJ. You can run a quicker et with a taller tire if your engine has the hp to pull it. Which this truck did.
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miltonwaddums
Dodge Dakota
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5/04/2008
17:23:05
|  RE: Looking for better fuel mileage? Help.
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How do you lower the area under the torque curve and get better 1/4 times?
I'm calling BS. And I try not to do that for the most part. I've tried to run scenarios through my head where it would help, but theres just no way. Taller tires will kill quickness (so long as traction is unaffected) by reducing the amount of torque at the wheels and by increasing rotating mass. Thats all there is to it.
J
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SDave
Dodge Dakota
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5/05/2008
13:15:00
| RE: Looking for better fuel mileage? Help.
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Because the engine had the power to pull a bigger tire. You are assuming that I started with the best choice as far as tire size to begin with. I knew the guy that owned a local gas station and he mounted the old 275's on my spare rim and a friend of mines spare rim. I was wondering if the difference in tire size made any difference or if I was imaging things. I went out to the road outside town where we had the 1/4 marked off and raced it against a 94 Z-28. Won by 5 lengths. Came back after changing over to the 275's and raced again. Won by at least 8 lengths. Spun the smaller tires off the line considerably as opposed to the larger tires which were easier to hook up off the line. Nothing I couldn't compensate for the most part, but it was not leaving quite as quick with the smaller tires due to spinning. If you don't believe me, put a smaller tire on a Dakota that is running good et and mph and see what happens. Assuming you are running the right tire to begin with.
Here is another example: A friend of mine has a Duster that ran a best of 8.28 @ 163 in the 1/4. Usually run anywhere from 8.34 to 8.28. He noticed that over time that car went quicker. It was running 8.46-8.48 to begin with. He checked his slicks and the slicks were about an inch shorter in tire height compared to a set of new slicks that size. NOW he initially went to a bigger tire (why? it is not what I would have done but...), but the car really wanted a lower gear. He was running a 5.13 gear. Went with a slick that was 2 inches taller than the slicks he was running and the et slowed to 8.54. I forget the mph. Dropped in a lower set of gears with the taller slicks and ran an 8.05 @ 169 mph.
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Kowalski
GenIII
5/05/2008
17:43:49
| RE: Looking for better fuel mileage? Help.
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SDave - by that logic, it would be the first 1/8 in the 1/4 where the taller tires would make you quicker from not spinning. Not the "last 1/8" as you claimed earlier. That didn't make much sense to me either. Of course if you were hitting a rev limiter at the top end with the shorter tires, then it would make sense.
Lead, follow, or get out of the way
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jjj
Dodge Dakota
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5/05/2008
19:12:07
| RE: Looking for better fuel mileage? Help.
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Ok now you tell the rest of the story :)
Spinning off the line will kill ET.
"Went with a slick that was 2 inches taller than the slicks he was running and the et slowed to 8.54. I forget the mph. Dropped in a lower set of gears with the taller slicks and ran an 8.05 @ 169 mph"
This also makes sense as a lower set of gears is a steeper set - though not sure what he went to that is deeper than 5.13's.
If you mean he went to 4.88's and went quicker that is also possible - just depends on the engine/trans package.
A race car and street truck are very different animals.
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SDave
Dodge Dakota
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5/07/2008
16:41:42
| RE: Looking for better fuel mileage? Help.
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I could control the spinning with the smaller tires. It was just a lot easier to do with the taller tires. The taller tires I could get the truck to bark the tires once and then leave. The smaller tires I would spin mildly if I was careful( if I wasn't yea you would be talking about 2 lengths difference off the line) very briefly and then leave. All in all you are talking about less than 1/2 a car length difference off the line at best if I hooked like I should with the smaller tires. But like I said it was easier to leave with the taller tires and I could be more consistent every time. And the taller tires with the bigger circumference went faster on the big end.
No, he went with 5.38's. I was trying to get him to go with the 5.57's. He was leaving at 6400 and crossing the line at 7800-8000 with the 5.13's. The car was still accelerating when it crossed the line at the end of the 1/4 when the car had the 5.13 gears. I had been lobbying for him to go to a lower gear for some time. But he said he didn't want to turn the engine that hard. He didn't have the money to replace the engine if there was a major failure. He had like $22,000 in the engine. Then there was the fact that the more he ran the car and wore the slicks down, the faster the car went. When he replaced the slicks they were two inches shorter than they were when new. He ran that 8.28 on those old wore out slicks. It was quite obvious the car wanted lower gears. Between the fact that it ran faster times as the slicks wore down and got smaller and that it was still pulling well past the end of the 1/4 mile. It was a 7 second car no doubt. But it was quite a handful to say the least. And he thought for the longest time that it would be next to impossible to hook up if he went to lower gears also. It could have been better with a four link set-up. Somebody had give him a four-link years ago because they knew the car and wanted to see just what it would do if he could really hook it up properly. But he didn't want to cut up the car in order to install it. The engine is being refreshed right now and a few upgrades are being installed. There is a picture of the car where they build and sell Ram clutches in California. They have it there as a testament to how tough and durable their clutches are. They guarantee I think 100-150 passes on their clutches. The clutch in his car has over 500 passes on it. He races the car at Moroso Drag Strip in Florida.
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jjj
Dodge Dakota
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5/07/2008
20:18:37
| RE: Looking for better fuel mileage? Help.
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What engine is in the Duster?
6400 rpm is fairly low for a mopar, LOL
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scott
Dodge Dakota
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5/08/2008
17:28:04
| RE: Looking for better fuel mileage? Help.
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i was getting 14mpg city and hwy and i drive conservative. i just change my fan clutch (my old one died) now i get like 10mpg.?
this blows. i have a 2001 quad cab 4.7L w/auto. i drive my truck atleast 100 miles a day its my work truck.
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SDave
Dodge Dakota
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5/10/2008
16:14:47
| RE: Looking for better fuel mileage? Help.
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456 big block. 400 block with 440 crank with mains turned down. Indy cylinder heads professionally ported. 950+ horsepower.
I ran it four times against a Z-28 that runs low 14's high 13's at 98 mph. My Dakota ran low 13's high 12's at 106mph. I don't know how much sense it makes. It just happens to be what happened. I ran it twice with the smaller tires and twice with the larger tires. I had the MP cam installed and degreed to a centerline other than the one the cam calls for. Which made the truck pull harder in the midrange and top-end than if installed to specification. If you know anything about engines and degreeing cams, you should have some idea what I did. One thing for certain the cam does not want to be installed at 109. The cam would pull hard at any rpm range but it especially strong from about 2000-5500. It would pull hard to the red line in first and second. I was accused of running nitrous many times. The main mods I had were the MP cam degreed at ?, MP computer, dual exhaust, and injector sync set +12. I later installed underdrive pulleys, electric fan, 14 inch open element with K@N filter, and headers. The truck ran 12's after that. Just so you know when you run true dual exhaust, you encounter a lean condition due to the increased airflow. The computer can't compensate under normal conditions. I was able to trick the computer into richening up the mixture. I did this by unplugging the throttle position sensor repeatedly and plugging it back in while I revved the engine with the throttle linkage. You want to snap the throttle linkage so that the engine will rev to say around 5000, then release, and then repeat. All the while rapidly unplugging and plugging the throttle position sensor. The computer will eventually think that the throttle position readings are unreliable, go into limp mode, and start reading off the map sensor. I know this works on 92 - 95 model Dakotas. Not sure about the later Dakotas. It may not take the first time you do this. I know the first time we did this it took three or four tries before the computer finally disregarded the throttle position readings. If you have the air cleaner off when you do this you can smell the gas. At first, the computer will dump an enormous amount of gas for a few seconds and then adjust the air/fuel ratio. I have been trying ever since then to accomplish the same thing with different size injectors and fuel pressures. Basically because it be quite aggravating to do this throttle position sensor trick. You have to plug and unplug the throttle position sensor at a rather rapid pace. And have looked into trying a 360 computer on a 318 since the injector pulse widths on the 360 are greater throughout their range. But to date I haven't tried a 360 computer. 24 pound injectors didn't work. Thought I might try some 22 pound injectors. What year and what engine(s) did Mopar start using 22# injectors?
If you don't believe what I say about the throttle position trick, just any Mopar tech what would he think would happen if the computer somehow disregarded the throttle position sensor due to a faulty reading.
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