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Adding Onboard Air to a Dakota 3.9L V-6 Model


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As some of you already know, i have a 1994 4x4 dakota with a 3.9l, that i have been toying with the idea of adding an onboard air compressor and tank, to fill tires and run air tools intermittently off of, but my truck has A/C, and everything runs off one single serpentine belt, so how would i go about adding a good belt driven air compressor?

 

My durango has one of the small 12v electric onboard compressors, but that seems to take forever to even fill a portable air tank, and definitely wouldn't work to run an impact tool. I tried adding a 10 gallon tank in my durango, but it took over an hour to fill to 80 LBS. I can make or source brackets to mount the compressor, but would anyone know where i can get a pulley that i could bolt onto one of my existing pulleys, like the water pump or crank pulley, or even drill holes in my power steering pulley and bolt a v-belt pulley to the front of it? I know there is a post on here about using a york a/c compressor, but after looking at one, i don't see a way to add it to my truck, because it doesnt have a lot of room under the hood. One idea i did have, was maybe bolt the compressor down on the frame below the fan, but, to do that, it looks like the compressor would be running backwards, and i am not sure that would work.

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Well, an engine-driven approach will work, and I can see myself fabricating brackets to work with the OEM belt system or an add-on pulley.  There may even be a Dodge or Dakota truck pulley system that would work here, this is essentially a Chrysler LA V6/V8 engine design.  I'm envisioning decades of 318 and 360 industrial strength engine applications that might be out there...Kilby Enterprises has goodies for York air compressor systems, including a bracket kit for the V-10 Chrysler engines.  You might look at the Kilby parts available and see if any would work with your Dakota 3.9L V-6.

 

If you go it yourself, work would entail aligning and balancing the pulleys, using the right York compressor (they mount upright or horizontally), addressing the belt load to assure reliability, correct hardware, adding a reservoir and plumbing as you describe, and so forth.  I would not mount to the vehicle frame, as the engine moves in relationship to the frame, and belt tension would be impossible to control.  Onboard, engine driven means engine mounted.

 

There is an alternative, and I have it:  a York compressor powered by a 12V motor.  This unit was commercially built, and I looked online for the supplier without finding a listing.  (If this sounds appealing, I'll take photos, share more details and research current sources, if any.)  The entire setup stores in a sealed military canister.  I have the available add-on tank. 

 

You take the compressor unit from the canister and use an Anderson plug to connect to your vehicle's high amp battery source.  (Warn supplies Anderson plug cable kits to 20' length.).  The compressor can be hooked to either end of the vehicle if you have heavy Anderson connectors at each end.  This provides York-grade air volume and also the option of a reservoir tank for reserve when running air tools. 

 

On this same note, ARB now offers the twin-compressor system for 12V, higher volume air supply.  Though certainly not an industrial strength York compressor head, this will handle light air tools and can be used with a reservoir, too.  Imagine: You get to hear two ARB air compressors talking to each other at the same time!

 

There are also other 12V compressor solutions.  This is an option to engine mounting issues and does reduce vehicle fuel consumption, the same principle as a Ready Welder versus an onboard, engine driven frequency welder that puts a good load on the engine's high output alternator and burns fuel the whole time you're welding.  There are pluses and minuses to both.  Think of the electric compressor systems as something akin to a diesel-electric locomotive:  The engine is simply running the alternator for a battery supply system; the compressor is electrically powered.

 

Moses

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I was talking to my neighbor about this, and he has a version of the york that is belt driven off a 110v electric refrigerator motor, that connects to his truck with a power inverter, and after looking at his, i may go this route myself. I have an in bed tool box, that after measuring it today, has quite a bit of room underneath that looks like i could use that space for, instead of trying to cram everything under the hood. I already have a dual battery setup in my truck, with the power inverter out of a 20 foot camper wired in to run other things off off, so i don't see where adding an electric motor would be that hard to do, but until he showed me his set up today, i never even thought of doing it that way. The upside is, it looks like when i get the new aluminum tool box im looking at for my truck, i can just relocate the compressor to the inside of it, and then it will be out of the weather.

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Interesting...What's the amperage draw for the refrigerator motor?  I'm trying to estimate the battery and alternator load and how much draw is involved for the inverter.  Typically, the compressor runs for relatively short periods unless you're doing a major repair job.  We can do the math on how much battery and alternator output this compressor and motor require.  Of course, there's some energy lost with the battery and inverter process, but that's a trade-off.

 

Did the refrigerator motor's power and the pulley ratio enable the compressor to run air tools directly?  Or does he use a storage air tank, too?  I'm curious about the pulley ratio and actual speed at the compressor's crankshaft.  Putting the compressor and motor in an enclosed area sounds safer, out of the weather and a finger saver. 

 

You will need cooling of some kind in that closed space, optimally for both the electric motor and compressor.  The York units do not have anything more than engine fan air movement.  The pulley and clutch do not have fan blades like a generator or alternator pulley uses.

 

Moses

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I will have to look into what the draw would be, as i didn't think to consider that. I do know the inverter i am using is an older design, from an early 1980's era tow behind 24 foot camper that i tore apart, but i havent really looked at it enough to know what the specs are for it. i will have to do that this weekend when i get a few minutes, and let you know.

 

I don't know if the set up he is using will allow direct operation of air tools or air accessories, because he has it connected to a custom underbed tank. It is on a regular cab 1996 ford, and he mounted the tank where the spare tire normally goes.

 

As for how to cool it, what i am looking to get is a deep well aluminum bed box, and my plan for the compressor was to build a box in a box, and use a 12v electric fan at the bottom of the tool box to help with cooling. My neighbor can build almost anything i need, so i was thinking a box to fit the compressor and motor in, with a top over it so i can set stuff on it without having it fall on the compressor, and build the compressor on a support, with a fan underneath to draw in cool air and vent hot air. I don't want to put the fan in the top, or in the side, because im afraid all that will do is draw in water and cause issues. Another idea i had, taken from some high end computer cases, was to use large computer case fans, which are 12v anyway, and have them attached to exhaust ducts out the bottom of the box.

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Curious about the inverter wattage and motor draw.  You might consider a battery management system if you do not already have one for your dual batteries.  With the air compressor running and working on a field repair with compressed air, you could lose track of the battery charge state.

 

Your neighbor's use of an auxiliary tank makes sense in any case, as you do need to stabilize the air volume available.  One kind of tank that I've seen in use (just happens to be RareC8's Jeep Scrambler) is from an 18-wheeler tractor's brake system.  He's cross-mounted the tank between frame rails, uses quality air line to the NPT ports, and it all works nicely without a huge expenditure!

 

I like your idea of the computer fans and ducting.  Your road salt and winters mean that no sheet metal can withstand exposure.  I'd avoid drilling vent holes to the undercarriage if possible, if absolutely necessary to do so, seal the metal well! 

 

Moses

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One thing i did forget to add, is that my truck has a custom alternator set up. I have a friend who owns a starter, alternator, and generator rebuild shop, and with his help, because of the dual batteries, the stereo, which was really a waste, since i usually leave the amps off anymore, and the plow, which i forgot to mention, and is a Meyers electric over hydraulic, and the extra lights, and the dual screen dvd system i installed for the girls for long trips, he set me up with a 145 amp alternator, and using the inverter, i have run a full size fridge, TV, cable box, and home stereo, all at the same time, for 2 full days on one occasion, while my folks' house was being rewired.  Even with the truck running, it never seemed to draw much on the truck. It idled away fine at 650 rpm, and even when the fridge kicked on, it didn't seem to drop rpm at all.

 

I originally built this set up at a time when i couldn't really afford a generator, and i had all the components except the alternator, to use as a backup generator if our power went out in the winter, or if we needed to power something in one of our middle of nowhere winter adventures. It also, to me at least, was functional as a heat source in case the power went out while we weren't home in the winter. I could leave the girls in the truck while i set up to run the basics in the house, and they wouldn't be freezing. So far, i have had only one issue with it: if i try to draw too much juice on any one circuit, it will pop the fuse, but that is no different than if you try to draw too much juice in your house, it will trip the breaker.

 

I really should describe my truck here. I bought this truck in southern PA, so it wasn't all rotted when i got it, and since then i have done a complete, what i call frame off winterization. I took everything off the frame, undercoated the bottom of cab, bed, and inner fenders, and also cleaned and undercoated the entire frame. I plan to keep this truck a very long time.

 

The bed box i'm looking to get has at least 6 to 8 inches of clearance between the box floor and the bottom of the tool box, so i won't have to cut into the floor of the bed at all for ventilation. I'm figuring the space between the bed floor and the bottom of the tool box should be sufficient for ventilating purposes.

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Every time i have an idea, you come back with 2 or 3 other ways i didn't think of to make my ideas work in a plausible manner, and, unknowingly, most of your ideas will also save me a ton of money! I was thinking of what kind of tank to use for an air system, and researching tons of different ideas, and never thought of trailer air brake tanks, which my step dad, being a tractor trailer owner, ex-driver, and mechanic, has all kinds of that stuff laying around in his barn. He owns a custom 1969 Peterbilt that has onboard air, which is where i originally got the idea for doing an air system on my dakota.

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As for a battery management system, i use a battery bug unit, that not only has a display, but also has an audible tone, to alert when the batteries drop below a certain voltage. I use Optima deep cycle marine batteries in all my vehicles, but i have had times in the past where i have been somewhere, was either using the lights, or at an outdoor party or bonfire, using the stereo, and wound up with a dead battery, and have gotten stuck a few times, so when i built my 1991 dakota, i vowed that would never happen again, and i transferred everything to this truck when i got rid of the older one.

 

It took me awhile to find the info on the inverter, since the company was bought out a few years ago by tripplite, but here is what i have found. The inverter has a continuous running wattage of 1800, and a 5 second peak of 3600. i also have since found out the inverter i have was added to the camper we tore apart, because my brother has the same model air stream, only 2 years newer, and his doesn't have an inverter in it, only a converter. The inverter didnt have any specs on it anywhere, just a make and model, which is why it took me so long to find anything on it.

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Does the Battery Bug provide an automatic switch-over when batteries get low?  That kind of management actually saves enough voltage at one battery to start the engine.  "Automatic", the full management systems take the guesswork out of battery management and provide a means for storing a re-start without your having to monitor gauges or listen for a beep while the party is going on!  The automatic switching systems work well for winching in the remote back woods.

 

As for deep cycle batteries, do you use this for your main vehicle battery?  There's controversy about deep cycle RV or marine batteries preferring a complete discharge before recharging—unlike an automotive battery that constantly gets drawn down slightly then brought back up.

 

The inverter sounds like around 16 amps of available 110V current...If that's enough, you're in business.  I have an inverter from Harbor Freight that's 2000W continuous and 4000W short peak.  This model goes on sale occasionally for around $130.   If your inverter does not hold up, you might look here... 

 

Moses

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Actually, all the battery bug does is connect directly to the battery individually, and allows me to monitor each battery separately. I have been saying for quite awhile, ever since i had my first Dakota, probably 10 years ago, i was gonna set up an automatic battery monitoring system, and every time i plan on doing it, something else comes up, and it never gets done. its one of those where i know it would be beneficial, and worth the money and time, but at the same time, its one of those where do i get that for the truck, or spend the money on the house, and usually the house wins. But, the house is finally done, at least to the point where i'm not spending every spare dollar on it that i get, so i'm looking into not only the battery system, but the other things i have mentioned in other posts as well.

 

As to your question about the deep cycle batteries, the ones i use aren't the marine or RV deep cycle batteries. Optima batteries makes a line of automotive deep cycle batteries, that are mainly for the guys with huge stereo's or large amounts of onboard lights and electronics, and those are the ones i use. They are the Optima Yellowtop batteries. They have a 120 minute reserve time at half charge, 750 CCA, and 900 MCA. I have run the front lights (4 combination fog/driving lights), and the stereo, which is about 1200 watts peak, i wont get into the full specs here, for a continued 4 hours, and had no problems starting the truck. I have the batteries set up through a switch system though, so if i drain one, all i have to do is flip the switch, start the truck, and then flip back to the other one to let it charge. I never run it so that it drains both. i learned my lesson the hard way with that in my first Dakota.

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The switch system is sold as a kit by several different companies. You can find them under switchable dual battery system, or dual battery switch system, just by doing a search in whichever search engine you use. I know a lot of the guys i talk to around here like the automatic set up, and it does seem like less of a hassle, but i am out in the middle of nowhere quite a bit, and usually by myself, so for me, the switch system seems to be a better choice.

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