fuel mileage

[stmitch]

As an ME, I'm sure you know this, but for the sake of transparency in this experiment, you should keep everything but your fuel the same as it has been. So drive the same route, speed and style that you'd normally drive. Then you'll have a reasonably close to an apples to apples comparison.

That being said, the biggest factor in highway fuel economy is aerodynamics. The second biggest is engine rpm. Both are negatively affected as speed increases. Rangers aren't very aerodynamic, so driving 75mph is really dragging your economy down vs driving 60 mph. In fact, it's exponential. The faster you go, the more the air works against you. Slowing down, or focusing on improving the aero of the truck will likely have bigger gains than tweaking fuel chemistry. Changing the gearing of the truck to reduce engine rpms at highway speeds would be effective as well, but mechanical mods are typically more expensive than aero mods, and certainly more expensive than just changing your driving style.

Please report back once you've run a few tanks through to deliver your findings, whatever they may be.

 

[chewy012]

Yes I plan to do a full write up after a few tanks explaining and keep consistent with as many variables as I can, it'll be a few weeks to get a decent number of tanks gone through. I've done a few aero-mods that I'll touch on later, have not noticed benefit from though.

I am a tool fool. I always have my tools and stuff with me because I can't decide what I will or won't need in a pinch, should one occur haha. Ever long mental debate with myself haha



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[chewy012]

Just checking in for anyone keeping score. I'm still testing, haven't given up. Will post a write up.... again, for those keeping score haha

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[chewy012]

Ok, at this point i think i've got enough information on this. So here's the set up and what my results are. Also, this won't be the most scientific thing you'll ever read, sorry.

First off, for those who want the quick answer, acetone really does not improve your fuel mileage...

1992, Ranger extended cab
4.0L OHV
M5OD-R1, 92 Rear Axle - 3.08:1
205/75R14 Tires
2WD

Ok, so I tried to keep my driving as consistent as I could, however, through the course of my testing i encountered traffic jams on the highways, really windy some days, sometimes morning, sometimes afternoon, mostly perpendicular to travel. Mostly highway commuting to work, 20% below 55, 30% 65 -70, 50% 70 - 80 mph. rough estimates, i did not count miles to get those percentages. I drove with the tailgate closed, and an empty bed.

While i tested my tanks, i gathered some information comparing acetone and gasoline. The myth about acetone having less surface tension and thus reduces the gasoline's surface tension in order to make it burn more completely is just false. acetone has a surface tension of 0.024 N/m, Gasoline's is 0.022 N/m.

In general, comparing any properties of the two considering the respective weight percents of the mixture. Any pro or con of the fuel mixture will only be negligible.

Keep in mind, the information i found on gasoline is rough estimate. Gasoline's have proprietary blends, so shell, conoco, excon, sinclair, BP will all have there different mixtures. Gasoline is basically mix of various hydrocarbon fuels. For the most part i used the same gas station every tank, but i'll be honest i don't even know what brand it is.

ok, so this is a comparision of the two fuels at a 400:1 ratio;

The density of Gasoline is about 46.176 lb/ft3 and Acetone is 49.30 lb/ft3. With a 400:1 ratio, the mixture should have a density of 46.18 lb/ft3, which isn't enough to make a difference on the A/F ratio.

Gasoline has a Heat of Combustion of 20.2 MJ/kg, while Acetone has 13.1 MJ/kg. The mixture should have an Energy Density of 20.1 MJ/kg. This would indicate that you would loss power and use more fuel, again though, negligibly.

Looking at the heat of vapor, Gasoline's is 330 BTU/lb while acetone's is 220 BTU/lb. Final mixture should have a Heat of Vapor of about 319.8 BTU.lb. Suggests the mixture would evaporate easier, it's still negligible.

Now, here's a look at my tanks;
1st) 895:1 mixture, 154.7 miles on 7.5 Gallons - 20.63 mpg.
2nd) 545:1 Mixture, 360.4 miles on 17.4 gallons - 20.7 mpg
3rd) 390:1 Mixture, 157.9 on 7.6 gallons - 20.8 mpg.
4th) 612:1 Mixture, 334.7 miles on 16.2 gallons - 20.7 mpg
5th) 2680:1 Mixture, 317.8 miles on 15 gallons - 21.2 mpg.

While no tanks are ever created equal, I tried to keep as smooth and fluid of a driving style as possible. I monitor throttle position with a vacuum gauge, and I flow with traffic. There's a lot of hills on my commute, both ways, so I hold the pedel and let my truck slow down up hill and speed up down hill. Elevation changes on my commute by 1200 ft.

It's a bit of a guessing game coming up with mixtures. Since I was adding acetone to the tanks before the gasoline so I could get good mixture, I had to predict how many Oz of acetone I would add to get a certain mixture. Add the gasoline, assuming the pump will always stop at the 21 gallon tank capacity, give or take. Then by knowing the amount of acetone you added, and assuming always 21 gallon total, give the final mixture approximation. From tank to tank i take how many gallons it should take to fill 21 gallons (projected from the gas gauge), calc the amount of acetone still in there, calc how many more Oz of acetone to add to make a final ratio, and then recalc based on how many gallons i actually had to add to fill the 21 gal.

Anyway, short story - long, there isn't any real noticeable improvement. With all the uncertainties that I was not able to account for, the results are negligible. I have noticed that my tank needle moves more uniformly. I think there may be a nice cleaning effect from the acetone as it is a great solvent for both polar and non-polar molecules. Before this, i generally keep my fuel system pretty clean as it is, Lucas injector lube about twice a month, fuel filter is 6 months old, injectors are 10 months old, new sparks, wires, air and oil filters.

 

[alwaysFlOoReD]

Thanks for the update.

 

[stmitch]

Good info. Thanks for checking back in and setting us straight! TIme to get to work on those aero mods now.

 

[Mark_88]

Yes, thanks for the follow up...

I just noticed you are running a K&N filter...is this an older filter that may have some air flow issues by any chance?

I had two of them from two different trucks...the flat rectangular and the round cone style. I tossed the round cone style and went with the flat rectangular one that fit inside the air box for my 96 project...I figured if I had to I could always revert to the old paper style if the K&N got plugged...but I hadn't yet tried the restore process so I wasn't sure if it was clogged with crud.

Probably as large a factor in fuel economy as any of the other possibles...

 

[chewy012]

Oh good question, I didn't touch on that...

I actually switched back to a regular Wix filter about a week or two before I started testing. I'm now a believer of the "k&n's screw up your MAF".

I was getting random CEL's and I replaced nearly every sensor except the MAF... cleaned it, regularly, no help. Popped in a junk yard MAF with the Wix and no more problems.

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[chewy012]

Good info. Thanks for checking back in and setting us straight! TIme to get to work on those aero mods now.

Yes aero mods. Not sure they made any difference, I did them about the same time I swapped my MAF and filter.

Basically took a junk yard bed liner and cut it into skid plates. Front, belly, and rear. Intent was to improve air flow under the truck. Belly pan goes from the tranny cross member to about the fuel tank, 4' x 4' roughly. I was afraid of trapping heat under the tranny.

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[chewy012]

I've got more bed liner plastic that I'm thinking of making fins with, in an attempt to redirect air away from the pumpkin and under the axle better.

Annnddd on a note back to the study I did, those mpg values are more or less what I've been getting since I bought the truck almost two years ago. Weather depending, but 19-21 mpg is my yearly range...r.

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[stmitch]

The most effective aero gains will start at the front of the vehicle since that's the leading edge the air is fighting. An undertray to clean up the airflow under the truck is a great idea for a discrete aero mod, but just having one in the middle probably isn't going to do much since the air still has to pass by the messy front suspension, engine, and trans. Then it hits your undertray where it becomes more laminar, and then gets tossed around the rear suspension, axle, and exhaust on the way out. The most effective design would start at the very front, and work it's way back as far as you're comfortable.

Since you're concerned about heat building up, maybe take another approach? Instead of trying to improve airflow under the truck, you can direct air around the truck too. It will achieve much the same thing. So, an airdam up front with some side skirts to keep the air out would work too. It would be more noticeable than the undertray though.

Maybe consider a partial grill block too. They're typically very effective.

And work on tightening up any excessive panel gaps. The front bumpers tend to hang pretty low on Rangers, and can usually be raised to tuck in with the grille/body better.

 

[chewy012]

^yep, I do have a front skid, and some small fins to try and redirect air around the tires, I am however looking for the discrete look. A rear one as well to cover the spare tire and act as a diffuser. I don't think it's that good of an actor though.

I think it's gonna be an on going project. Something I can easily tinker with, I can not tinker with stuff.

I really like the bed liner material though, it was $30 at the junk yard and I just rip through with a jig saw. Kind of fun and if its all for nothing and Chuck it all, I'm only out $30.

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[stmitch]

If it's open just in front of your rear most panel, it could be acting as a parachute and dragging your numbers down, but it's hard to say without seeing more of it.

The plastic bedliner isn't a bad idea. You can get brand new coroplast sheets in 4X8 for less than $30 in most cases too. http://www.homedepot.com/p/Coroplast-48-in-x-96-in-x-0-157-in-White-Corrugated-Plastic-Sheet-CP4896S/205351385

Or, since it's campaign season, find as many campaign yard signs as possible and go to town. It's the same stuff.

 

[chewy012]

Yeah, the cool thing about the bed liner is there are already molded corners and what not (wheel wells, etc.) that you can make fins, chutes, or whatever.

I did think of that sign material originally, but couldn't think of what it was called or how to describe it haha

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