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Old 09-14-2009, 11:15 AM   #1 (permalink)
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Join Date: Aug 2008
Location: Kc KS
Posts: 148

Dart Lite - '76 Dodge Dart Dart Lite
90 day: 18.34 mpg (US)

Beater..with a Heater - '94 Isuzu Rodeo LS
90 day: 16.19 mpg (US)
Thanks: 4
Thanked 7 Times in 5 Posts
MPG experiment, 1976 Dart Lite

I started this a while back on my Mopar forums. I am going to post the previous stuff, and then start back where I am now.


I have an almost stock Dart Lite. 225 /6 with 3 SPEED and 7.25 rear end.
The car is manual steering, manual 4 wheel drum brakes, and very little options (3 speed wiper and 3 speed transmission were only primary options) Only "upgrades" so far are the modern radial tires, and a "dual" exhaust that splits into a Y where the stock converter would have been, through glasspacks out the rear. Exhaust is in line after carb, and distributor modifications, with a GOOD dual or bigger single system with better mufflers.

Since this was Dodge's MPG car, that is what I am going to start to do...Tune it for better mileage.

As run, it has 15" ralleye wheels, small bolt pattern. The drum brakes have been gone through COMPLETELY, and now stop EXCELLENT.

Dart has received a basic tune up consisting of:
•plugs
wires
cap
rotor
fuel filter
air filter
oil change
I adjusted the valves to quiet it down, i still have one or 2 that are clacking, so I need to go back with the feeler gauge, and get them adjusted properly.
I also had to run the idle a little higher then I would like to make driving easier, as it would not leave a stop at low idle. Investigation led me to no accelerator pump function.
First full tank, of 35% in-town driving, and 65% highway, (with stop and go, but most highway is 35-55 consistantly) MPG was 13.5

Long Terms goals:
I am going to swap the 4Speed OD that I bought with the car, once I have maximized MPG in the current configuration. I also bought 8 3/4 rear with 3.55 (3.23 also available) rear end that I want to go in later. Eventual plans are Turbo stock /6, and 8.75 may wait until then, or in sooner if the 7.25 gives up sooner.

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Old 09-14-2009, 11:17 AM   #2 (permalink)
EcoModding Apprentice
 
Join Date: Aug 2008
Location: Kc KS
Posts: 148

Dart Lite - '76 Dodge Dart Dart Lite
90 day: 18.34 mpg (US)

Beater..with a Heater - '94 Isuzu Rodeo LS
90 day: 16.19 mpg (US)
Thanks: 4
Thanked 7 Times in 5 Posts
Next phase, next tank:

I am going to start with Carb. Mileage on odometer says 41K, so presume is 141K.

I started with carb teardown. There is extra "Stuff" on it. I will post pictures later. During teardown, I noticed coat hanger material wrapped around the choke shaft, and throttle shaft, several times. WTF.

As I tore into it, I found 2 of the 3 bolts that hold the carb base to the carb main body were stripped.

So I took off the extra "stuff" and separated main body / upper body / base, and set them into the carb soaker cans. Main and upper look AWESOME
I am going to tap out the main body, to a larger size for new fasteners, and rebuild carb, then run for next MPG update.

Next up is to start with some of the distributor and ignition modifications.
I think the HEI will be next.

Ideas are welcome, some might be tried some might not.
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Old 09-14-2009, 11:18 AM   #3 (permalink)
EcoModding Apprentice
 
Join Date: Aug 2008
Location: Kc KS
Posts: 148

Dart Lite - '76 Dodge Dart Dart Lite
90 day: 18.34 mpg (US)

Beater..with a Heater - '94 Isuzu Rodeo LS
90 day: 16.19 mpg (US)
Thanks: 4
Thanked 7 Times in 5 Posts
2nd round has begun. I filled up Tuesday Morning.

1. The carb is rebuilt and installed, with the exception of the accelerator pump rod, which needs to be fiddled with. I am running one of a Thermoquad, as the carb did not have one upon purchase. All of the bolts holding the baseplate to main body, and top plate to main body have been tapped out and have new bolts.

2. Tire pressure has been adjusted to 35 PSI on all 4 corners. I wanted to leave it alone for the purity of the test, but could not in good conscience leave them as bought. Even thought they looked fine, they ranged from 15-18 PSI Tires max pressure is 44, so I might run them up to 44 down the road to see the effects. The manual steering is much easer now, I can almost turn it one handed.

Conclusion, I will fill up Thursday evening, and compute mileage. I now have a book, to keep MPG and notes. Update soon.
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Old 09-14-2009, 11:19 AM   #4 (permalink)
EcoModding Apprentice
 
Join Date: Aug 2008
Location: Kc KS
Posts: 148

Dart Lite - '76 Dodge Dart Dart Lite
90 day: 18.34 mpg (US)

Beater..with a Heater - '94 Isuzu Rodeo LS
90 day: 16.19 mpg (US)
Thanks: 4
Thanked 7 Times in 5 Posts
UPDATE

I could not wait until this afternoon. I topped off at same station, same pump, with same routine. 54 miles on 2.97 gallons = 18.18 MPG.

Previous was 13.5 mpg.

Adjustments made between 13.5 and 18.18 was tire pressure, tires were under-inflated and the carb was rebuilt. Basic parts store rebuild kit, on a 1945 Holley.

Stock, this car had 6.95 x 14 tires, which converters to 25.3 OD if I understand correctly. Currently, tires are 235/60/15, which convert to 26.1 OD. 26.1 / 25.3 = 1.03 or 3% taller tires.

This changes the baseline to 13.9 MPG, and the current to 18.72 MPG.

Next up: Identify gear set, and fluid change in both differential and transmission. Who knows how much better it will shift and drive with new fluid.
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Old 09-14-2009, 11:24 AM   #5 (permalink)
EcoModding Apprentice
 
Join Date: Aug 2008
Location: Kc KS
Posts: 148

Dart Lite - '76 Dodge Dart Dart Lite
90 day: 18.34 mpg (US)

Beater..with a Heater - '94 Isuzu Rodeo LS
90 day: 16.19 mpg (US)
Thanks: 4
Thanked 7 Times in 5 Posts
MPG on the last tank, 19.60 per odometer, 20.18 corrected for tire size.
This was combination of city and highway. AM highway was cruising at 55 MPH for the most part. PM highway is more slow and go, 25-35 mph average.

Changes....
Transmission fluid (drained out 5 ounces, took 85 to fill it back up )
Differential fluid (ok fill level but dirty)

Both were done mid tank, so their benefits were partial. I was hoping to get new exhaust run this weekend, but it might not work with finances.

Next up will probably be the HEI ignition modification. I am also going to duct air up to air filter housing, to see if that helps.

I am not quite ready to dive into the timing modifications just yet. I have to work my way up to that (new, scary )
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Old 09-14-2009, 11:25 AM   #6 (permalink)
EcoModding Apprentice
 
Join Date: Aug 2008
Location: Kc KS
Posts: 148

Dart Lite - '76 Dodge Dart Dart Lite
90 day: 18.34 mpg (US)

Beater..with a Heater - '94 Isuzu Rodeo LS
90 day: 16.19 mpg (US)
Thanks: 4
Thanked 7 Times in 5 Posts
Trans fluid was NON EXISTENT. I am running standard fluid for now, I will switch over to synthetics once the transmission and rear end get "cleaned out" with the new mineral fluid.
Wheel bearings front were repacked with the front brakes, rear are due to be checked when I switch to synthetic in rear differential.
Tires are all spot on at 35 PSI. Tire sidewall says max of 44, I might work up there later. There is a lot of "opinions" on that matter on the thread on slantsix.org.....
I want to rebuild suspension later, throwing sway bars, etc into the mix....I wll have alignment set after rebuild.
Brakes could very well be dragging a little, I went to extremes to make sure this 4 wheel drum car would stop in daily traffic. They will also get checked, and drums turned as part of the evolvement of this experiment.
Air intake is next, going to duct air to stock air box. I am not going to spring for a K&N right now, because it would be a waste of money once the turbo come in this winter. For now, clean paper filters, with a little forced air might help. I can't wait to see the difference between the 3 speed and the OD, to actually document the difference.
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Old 09-14-2009, 11:28 AM   #7 (permalink)
EcoModding Apprentice
 
Join Date: Aug 2008
Location: Kc KS
Posts: 148

Dart Lite - '76 Dodge Dart Dart Lite
90 day: 18.34 mpg (US)

Beater..with a Heater - '94 Isuzu Rodeo LS
90 day: 16.19 mpg (US)
Thanks: 4
Thanked 7 Times in 5 Posts
Hit the gas station this AM.
Same station as past 4 fillups. Same procedure, fill on low speed, until it shuts off, and then one more slow until it quits.

206 miles on 10.5 gallons...19.61 plus the conversion for the tire diameter of 3% = 20.19 which is best so far.

I had a test running by accident. A while back I took off the air cleaner, to mess with the accelerator pump linkage, and clear out vacuum lines. I forgot to put the air cleaner back on. I knew it was there, but it got lost in the shuffle with the twins coming, and I just plain forgot. If I reference this tank as #4.
Tank #4 was 20.19 mpg
Tank #3 was 18.16 mpg
Tank #2 was 17.28 mpg
Tank #1 was 20.18 mpg

So, the 2 tanks between previous best of 20.18 and now best of 20.19 were down, 11% to 15%, and these were the tanks when the stock air cleaner with parts store paper filter was off.

So, my Sheer-Luck deduction tells me that the air cleaner provides better mileage, then an open carb.
Feel free to call me a rocket scientist
I presume it is for 2 reasons, the velocity inside the tube, and the contour of the base of the air cleaner, streamlining air entering the carb
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Old 09-14-2009, 11:49 AM   #8 (permalink)
EcoModding Apprentice
 
Join Date: Aug 2008
Location: Kc KS
Posts: 148

Dart Lite - '76 Dodge Dart Dart Lite
90 day: 18.34 mpg (US)

Beater..with a Heater - '94 Isuzu Rodeo LS
90 day: 16.19 mpg (US)
Thanks: 4
Thanked 7 Times in 5 Posts
This is where I stand right now. It was too hot (black vinyl interior) to roll this middle of summer. I drove it hit and miss when when weather was not blistering, but not enough to document.
I am going to fill up today, and resume the test. I will make sure fluids are up to par, and check tire pressure.
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Old 09-14-2009, 11:58 AM   #9 (permalink)
EcoModding Apprentice
 
Join Date: Aug 2008
Location: Kc KS
Posts: 148

Dart Lite - '76 Dodge Dart Dart Lite
90 day: 18.34 mpg (US)

Beater..with a Heater - '94 Isuzu Rodeo LS
90 day: 16.19 mpg (US)
Thanks: 4
Thanked 7 Times in 5 Posts
I figured I should explain my goals and objectives:
I grew up in the twin to this car, so when this one came about I snagged it. I am a gear head by birth, but eco by choice. Standard fare for this car would be to drop a small block V8 in it and have a hot rod. I love the basic reliability that it has so that option is out the window. It is a very early Dart Lite, with unusual factory configuration, so I am not doing anything I cannot reverse.
I want to make some small improvements here and there to get better MPG. This is not going to be an ALL OUT mpg build, but more of a "improve over stock". Body mods will be next to nothing, perhaps some underbelly, etc, but external core will stay put.
Ultimately it will get a used Grand National turbo. That way I can have HP when I want it, and MPG when I want it.

Next moves:
Synthetic fluid in trans and rear differential.
"HEI" modification (common in slant 6 community, using HEI module from GM products for hotter spark energy)
Index plugs
--Electric fan to replace mechanical. I expect this to have some significant rewards
wide band to check A/F ratio, perhaps jetting and timing adjustments.
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Old 09-14-2009, 12:14 PM   #10 (permalink)
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Join Date: Nov 2008
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The Geo - '93 Geo Metro
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Go ahead and up the tires to 45 or so. Removing the mechanical fan will have an effect, not sure if it's noticeable. I would run some seafoam through the engine.

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