MPG experiment....1976 Dart Lite

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Backtobasics said:
I would love to be able to run several tanks per modification, but that is not feasible for a couple reasons.
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Completely understandable. But you must understand that you're not going to be able to draw any useful conclusions because of the inaccuracy.

My mileage, fill-up to fill-up, varies as much as 2 mpg with NO changes to the car or route. The only way to get a reasonably accurate measurement is to average mileage over SEVERAL fill-ups, the more the better.

If you can't do that, then it's just not feasible to measure improvements with any accuracy after each modification. You'll have to see what the net result is when you're done.

Good luck! I hope you see some big improvements!
 
I acknowledge that this is not going to be be a "dead on balls accurate" experiment. I have to accept that fact that, this being driven on a every other day type of basis, that
  • weather
  • my right foot
  • my mental staus
  • humidity
plus the driving of other people are going to affect the number. Should Agressive Al decide to slam into the back of Cell Phone Celine, and cause me stop and go for an additional 30 minutes of my evening commute, I will have to live with that. The route driven is going to change, the manner in how it is driven will change, pure and simple. I will not come out and definitively declare that the "screen under the carb" is worth 2 miles per gallon.... But I will let you know how it affected the MPG on my vehicle....

The goal is an overall evaluation of the improvement of MPG, via improvementof vehicle tune, using standard and non standard principles.
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Disclaimer: This is a log of the MPG performance, and changes, on my 1976 Dart. Your results may vary, and your strategies, and methods may also differ. Use what you can. :)
 
Don't air your tires up to 44psi. That's the max psi you should put in them for the max weight they can carry. Sure you'll get more mpg but you'll be riding on the center of the tread patch to do so. By eliminating some of the tires designed contact patch ( also figured in to the max psi... only for greater weight ) you are getting rid of steering, braking, and cornering traction. At highway speeds you'll also increase your chances of a blow out due to too much pressure. Has anyone seen a picture of a regular radial tire at highway speeds? That is some scary $h!t. The low profile tires or ultra proformance tires aren't anywhere close to showing the amount of deflection that the "normal" (for most of our cars) tires have... and that's at the correct psi for load condition. If I find my adapter for my cell I'll snap a pic and post it.
 
Typical Friday AM fillup. Same station, same pump.

MPG down to 17.28
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This 2 week trip had more stop and go on highway, and then other days of highway at 60 MPH when I usually try to limit to 55 mph. This was first full tank with full fluid in tranmission and differential. I expected to see it better.

It is due for an oil change, and I might check out the plugs to see how they look.

Next major modification will be exhaust. It currently has a decent size pipe coming off the collector, that Y's off where the catalytic converter would be, and through dual 12" glasspacks, and out the back. It is probably 2-2.25 piping, and it is very pinched over axle, where it looks like the axle tube might have hit it at some point. The passenger side leaf spring is very weak ( I am running the coil over springs on the shocks) and the upper mount was tearing through the metal when I got it, so it validates the idea that it was overloaded at some point. It bangs and clangs, coathangered by PO, overall bad deal. It probably flows OK, but I am tired of the clanging.

I am having a local shop that mandrel bends do a system with a Magnaflow, out the back, driver side, SINGLE. I am torn between 2.5 or 3". I realize it is a bit overkill on a 1 bbl slant 6, but they can only bend 2.5 or 3".
--If I go 2.5 I can get the muffler and tip at n/c (vendor rep
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)
--If I want 3" I have to buy the muffler and tip, or I can have it turned down and semi hidden behind bumper. The system will be 2-2.5 off the the manifold to a flange and stepped up to the 2.5 or 3 around the transmision, so I can pull it off while fabricating turbo stuff, and re-install to drive.

I realize it is not the ideal change for order, since the existing exhaust is adequate flow wise, but this will be the last large expense I will be able to run on the Dart, since the twins are due in 5-6 weeks. I have a feeling all large purchases will be on hold. Little stuff might work, but the diapers and formula are going to kill me. I better get the exhaust run while I can....
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Back a thousand years ago when I was in college I drove a 65 Dart 4 door with a 170 and an auto. (gas was better then but) After I did a valve job on it it got 33 on the highway, and that wasn't running 55 either.

That being said, that was probably THE most underpowered car I've ever driven. It wouldn't have gone fast if you shoved it off a cliff with TWO rocks tied to it
 
Backtobasics said:
but this will be the last large expense I will be able to run on the Dart, since the twins are due in 5-6 weeks. I have a feeling all large purchases will be on hold. Little stuff might work, but the diapers and formula are going to kill me.
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Holy crap dude, I guess you'll finish this thread in a couple of years when you get a spare minute. I've got two friends with twins and they both disappeared for more then a year. I expect it will be the same for you....plan on it.

Oh and one little tip, try to use as little formula as possible, If you don't have breasts, then there's no use in you getting up a 3AM : )

Good thread, I'd like to see how it does with the OD 4spd.
 
Interesting thread. I'm liking the documentation of the changes and the results.

Don't recommend going the max rated air pressure on the tire bit. What you may save on fuel, you'll more the lose on accelerated tread wear in the center. Cornering and braking will be diminished as well due to the reduced contact patch of the tire.
 
Well, I am not disappearing. Driving the Dart saves me money, since it gets a little better MPG then the truck.

SLIGHT UPDATE, I have seen a decrease, over the last couple tanks. I just realized that when I was mocking up stuff underhood, I neglected to put the air cleaner back on. I have been cruising away, and didn't even give it a thought until I stumbled across it on the workbench. I have put it back on for most of this tank, so when I fill up I hope to see it back in the 20's courtesy of the air cleaner, and fluid in the trans and differential.
 
UPDATE​
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 :toothy10:
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.
 
This is coming back to the top.
It was just too damn hot this summer, so I drove the truck with AC.

I will fill it up tonday and start the tests again.
 
19.17 on the last tank.
I was disappointed.
We poked around under hood, and the PCV hose was plugged on carb, I guess I forgot to hook it back up. The blow by went to nothing! wahoo.
I also had some cracked vacuum plugs, so we fixed that, and while messing with this we noiced the entire carb was loose! I need to grab some lock washers for that. We adjusted the idle down, and air fuel mixtrure screw, the thing idles glass smooth.
I also noticed the oil was way low.
I jetted the carb up, it appears a small jet on this carb has the car into the powervalve a lot. I went from 62 to 64, I will run it with the 64 for this tank to see how it goes.
 
Dude, I am going to find a good vacuum amplifier and some other goodies for a care package if it kills me! PM me over on dot org, and I'll draw you up a vacuum diagram. It's all gotta be there, or your not going to realize the potential of the Dart Lite. Missing pieces make for the same mileage my race car gets. And your getting it without the 1/4 mile computed 247 hp. :shock: Of course your driving fifty seven feet, and I'm driving to Ottawa to match the economy! :-\"

If you haven't done the exhaust yet, stick with the smaller diameter. Anything on a single bigger than 2.5 is going to result in such low flow rates, your exhaust system won't dry out, and will rot from the liquid combustion bi-products left in the exhaust system.

The original feathers and lites ran a 2-1/4" head pipe and went back to the noodle over the axle. The gasses have cooled to the point that there is no back pressure penalty at that point. Keeping the velocity up will dry the system. For a mileage rig, don't mess with duals and so forth, unless your going to small diameter duals. That will still make more weight, and that's not going to help.

Get the timing set and distributor figured out first! One of these days your going to find a mopar nut in your area with a distributor machine, and the rest is going to be history! :-D

CJ
 
I just read the entire thread (great thread)... the only thing I can see that hasn't yet been mentioned is your wheels. I would recommend that you try to upgrade your wheels to something more light weight (i.e. aluminum mags). Those old steel wheels are heavy, and considering they're rotating mass the extra weight is that much worse. A light weight drive shaft would also help, and maybe some lighter drive pulleys (if you can even get them for a slant).
 
Ceej said:
Dude, I am going to find a good vacuum amplifier and some other goodies for a care package if it kills me! PM me over on dot org, and I'll draw you up a vacuum diagram. It's all gotta be there, or your not going to realize the potential of the Dart Lite. Missing pieces make for the same mileage my race car gets. And your getting it without the 1/4 mile computed 247 hp. :shock: Of course your driving fifty seven feet, and I'm driving to Ottawa to match the economy! :-\"

CJ
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you think you needall that crap for good mileage? guys on the slant site told me to get rid of all the smog stuff. i swapped to the super six but kept all the smog stuff, figured it was runnign fine with it, why scrap it all. so far i have gotten into the high 19s and thats it. i stuck a b body 8 3/4 in and seem to have lost mileage, i assumed it was 2.76 but i think i might be wrong. my speedo is off about 20% i never checked it before the swap either though but i didnt think it was too far off, if at all.
 
Ceej said:
Dude, I am going to find a good vacuum amplifier and some other goodies for a care package if it kills me! :-D

CJ
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Nice to see this is driving you nuts! Bwahahah!
autopar3000 said:
I just read the entire thread (great thread)... the only thing I can see that hasn't yet been mentioned is your wheels. I would recommend that you try to upgrade your wheels to something more light weight (i.e. aluminum mags). Those old steel wheels are heavy, and considering they're rotating mass the extra weight is that much worse. A light weight drive shaft would also help, and maybe some lighter drive pulleys (if you can even get them for a slant).
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Here is my quandry here... Small bolt pattern choices are few. Despite the year, it's all small bolt pattern. The 8 3/4 that goes in later is small bolt pattern too. It came with 15" ralleye wheels, with differing offsets front and rear.... It also has the early center caps, which really give it a nice stance, a little hot rod. Someone really did their homework specing out the wheels. If I go something else, I either have to use adapters, (200 bucks for 4) plus new wheels ($$) and the front wheels would almost have a FWD offset because of the spacers. All this to save a few pounds per corner.
OR
I go big bolt pattern (front kits run 250-300 plus extra parts) and new axles for 8 3/4 (200-400) and then I have all kinds of choices (I sell wheels, I can get drag lites or drag star knockoff for 85.00 each) but that still equals almost a grand.

:dunno:

It is a valid area to check on a MPG build, but I just don't know that the costs are worth the benefits right now.
 
SBP is certainly a challenge. Long term BBP is probably the way to go, but it does cost some money. I'm currently running SBP 14" ralleye wheels and I like them, but I've always wanted to go to BBP so I can get something in a 15" wheel.

I have a 14" set of vintage SBP mags I will eventually be putting up for sale (as soon as I can dig them out of the garage), but you're kind of far away from me so shipping costs would be an issue. And they're a "love 'em or hate 'em" style of wheel, so you might hate 'em.
 
The best I ever did was 29.5 with a 198 with everything stock in my Duster. Exhaust anifold was cracked and I had a split exhaust into dual turbo mufflers. 3:23's. Maybe my pipes are 1.75" Average highway was 25.5

Find a super 6 2bbl carb. Make sure it isn't one from a 318!! There is a difference.

I am doing research on HHO systems. A friend was running one on his '06 Cummins and pick up 2.5 mpg grossing 22,000lbs pulling a trailer.
 
Well, the experiment continues, and I found some ways not to increase mileage.

Namely, put in a bigger jet in the carb.:toothy10:

Rumor has it that the 1945 Holley dips into the power valve more frequently with a small jet. I guess stock is 57-60. Most upgrade to a 61 or 62. The carb had a 62 in it. I tried a 64, and mileage dropped to 17. My highway was a little higher then before, but not enough to cover this.

I am putting the 62 back in tonight, and then we may go down in size more, to find proper size jet for my driving style.

Remember boys and girls... bigger jets = less fuel economy. :toothy10:
 
A 64 sounds pretty big. I think I had a 61-2 high precision in my 1945. Just can't remember stuff that far back! :lol:

Have you checked in with Dan about one of the economaster carbs? The booster on the economaster will deliver better economy, and signal should be better for what you are trying to do.
I was never able to clear 18mpg with my '74 Valiant with the 1945 on it, but then I was running a noodle pipe, and no long distances. The Feather Duster single would likely have bumped it up. I didn't drive the car much 'till I had the Holley 390 on it, and mileage jumped up to the low 20's with a recurve and the bigger pipe.
Of course my focus was toward the drag strip, so I tuned accordingly, and I run the A904.

Have you got a current weight for the car? I'm going to toss a wag at 3400#. I still think you should be closer to 23 mpg with the three speed, but your short travel distance is going to make it tough to get there. Shoot, is the windshield defogged by the time you get there? :-D

Keep working on it! You'll get there!

CJ
 
Well, I haven't gone back to the 62 yet, I have been short on time.
I started tearing it down for flat black. I am spraying it tonight, but this entire tank has been the 64, so I will leave it with 64 jet for the test.

Once it is reassembled, I will take it for weight.

I am not going to buy a different carb for it right now, I still plan on going to the turbo. I do need to get the timing light to see where it is at, as it has never pinged, so I might be able to advance timing.

Daily drive is 15-20 minutes in on highwy, so the heater does work.
 
Enjoyed the thread, don't know if it is dead now. I had a Feather 5 or 6 years ago, great car, but I am not a duster fan. Mine got an honest 32 mpg on a highway trip from VA to the Petty place in Level Cross or Randleman. All stock but it did have radials and the timing was as high as I could go. Even ran a 17.75 at the dragstrip. I miss that bucket, always looking for a Dart Lite to run back and forth to work in.
 
Not dead, but stalled. The car had some fuel delivery problems (plugged vent on tank, failed fuel pump, and then carb issues.
I installed a sender for an aftermarket gauge in stock tank. The hole was cut to large, so the sender is in place, but if I fill the tank, it leaks at the sender.

I am going to epoxy in a patch so it does not leak, and then I will resume.
In the mean time, I have gone to synthetic in trans and differential, and section the old nasty dual exhaust, into a single system with a Dynomax welded muffler.

I will post more shortly when I get pictures off the camera.
 
Cool. I would be careful on the syn in the trans. They, the Experts, say the syn won't let the sycros slow down and the trans will grind when you shift gears. Chrysler started using AFT in the 70's in manual transmissions to cut friction. The rear should be fine with syn, but if you have a sure grip, make sure to use the Chrysler recomended fluid and additive for the cluches and cones.
 
And then they (Chrysler) stopped useing ATF in the manual trannys and went back to dino oil. Todays sythn. oils seem good to me, no issues with my 4spd.
 
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