Aeromod this, if you dare! (2004 Chevy 1 ton, cab and chassis truck)

[iamnotahippee]

I took some pictures of the truck bed this afternoon. ..they kind of suck because of the rain today.





Because of the installation of the tail roller that really messes with the shape of the back of bed. I need to lay some metal up on the side of the bed to see how it will shape up.
I need to look at my options also for something at the front of the toolboxes.
I figured mileage the other day, 9.7 mpg. That sucks! That all empty and unloaded for the entire time. I did some hauling, mixed between on the truck and using the trailer. And running pretty hard. Came out around 7ish. As crazy as it seems, being loaded really doesn't hurt the mpg all that much.

[JRMichler]

Originally Posted by iamnotahippee

I figured mileage the other day, 9.7 mpg. That sucks! That all empty and unloaded for the entire time. I did some hauling, mixed between on the truck and using the trailer. And running pretty hard. Came out around 7ish. As crazy as it seems, being loaded really doesn't hurt the mpg all that much.

9.7 MPG empty is very low mileage for a diesel one ton. How fast do you drive?

The small difference between loaded and empty is also unusual. What is the RPM at 60 MPH?

You had mentioned needing to do a lot of idling because of your electric winch. If you replace the two starting batteries with three or four deep cycle batteries, you will have plenty of power for the winch and for starting without needing to idle the engine.

[TimV]

+1 for upgrading the battery capacity.

Add 2 deepcycles for the winch.
Disconnect the deepcycles from the startbatteries for winching. After starting the engine, place them back parallel.

[iamnotahippee]

That mileage is airing it out at 75 or so. I do have an injector that needs replaced, and that may be having a small effect on the economy. I don't know what my rpms are at 60. In overdrive it turns somewhere around 2200 rpm or so at 70. I really wish the truck 4.10 instead of 3.73. It is bumping the red line at 60-65 in 4th gear, but drops out of the power band in overdrive. With lower gears i could cruise in overdrive loaded. I am going to start trying to keep a mileage log to see what is going on exactly. The injector may be having more of a hit on economy than i want to admit.

[freebeard]

+2 on the batteries.

Use an isolation relay. They're used in motor homes to separate the house and road electrics. One hypermiling technique is to not idle, even at stop lights. You have to be confident on your hot restarts though.

Think of the bed as a horizontal tailfin, like a '59 Chevy. Everything below the bed and behind the tire should look like this:



http://www.speedhunters.com/2013/06/a-brilliant-view-into-aerodynamics-2/

You might want to read the article on background, even though it's ostensibly about Time Attack cars, it really gets into the whys and wherefores.

AB: I would say the most misunderstood thing about aero for the general public is that people think there is one perfect shape and we [aerodynamicists] know what it is, so they are always asking you to tell them. The truth is, there is no good solution that isn’t a custom one and even defining what is better is circumstantial. We call the details of the car the packaging and packaging is the name of our game. Arranging things to make the aero work and making the aero work with the way things are arranged. Bigger is not always better and testing is king. I think that the real questions to ask are: why did this work, why didn’t this work like I expected and what is the next thing to try?

Let me explain about that a bit more. Initially aerodynamics seems so intuitive. If you put a flat plate inclined to the wind it makes downforce. So all you need to know is what angle makes the most downforce, the least drag or whatever. So in that sense a diffuser is intuitive. But it gets complicated when you have a suspension part protruding into the air stream, a dirty rolling tire wake, air coming from whatever of a million things in the front of the car or the car in front of you, hot air off the exhaust and a five mph cross wind at two degrees of yaw or half a degree pitch under braking. All this stuff interacts. It’s about how all the parts work together as a system so unless you understand all the parts you can get it all wrong.

30% of your drag is in the undercarriage, it says here. Also notice the high momentum mud flap. I've never seen that elsewhere.

[iamnotahippee]

I am not sure on the mudflap either. I am thinking some belly panning may be useful. Idle time is just a way of life with a diesel, or atleast a turbo diesel. If you are run in hard, the turbo needs to cool before you kill the engine to prevent excessive heat soak. Now excessive idling is detrimental also, so it is a fine line. The hard part about adding a bunch of big batteries is they take up alot of room. They can't go on the bed, there is no room under the hood. The only real option is installing another toolbox under the body and putting them there. Now that option is in the works, primarily to address a voltage drop issue I am having when I hook up my trailer and use the winch on it. I haven't done the figuring yet to see how much battery I would need, but it would not be unusual to need to run my 12.5k winch for 15-20 minutes on one sitting. It pulls enough juice that if I have it running under a good load for more than 30-45 seconds I have to let off and let the truck build charge back up.
another consideration is cost/benefit analysis. Driving 55 would help fuel economy, most definitely. But if you have 300+ miles to run in a day, the fuel economy hit of 65 mph sure starts to look miniscule, especially when you are oversized and can't run after dark. That 30 minutes could be the difference between making it home without a ticket or not. I do try to keep the speed down when time is not as much of an issue, but those times are somewhat rare.
Extra battery storage to reduce idle time...so probably looking at easily $150 each for batteries, twice if I add 2. Then $300 or more for a quality underbelly box. Conservatively $50 for the odds and ends to wire it all up. When I consider for $1300 or so I can get the injector replaced, the batteries get me half way there, and may be more benefit in the end.
I will say, on my empty mileage from above, 120 miles or so of that included going to help my wife after she had an accident on the way to work with our kids with her, and then me headed to work running very late. So I was definitely not driving for economy sake. I am hoping this week I can get some more numbers to pull from and see where we are economy wise.

[JRMichler]

Originally Posted by iamnotahippee

I haven't done the figuring yet to see how much battery I would need, but it would not be unusual to need to run my 12.5k winch for 15-20 minutes on one sitting. It pulls enough juice that if I have it running under a good load for more than 30-45 seconds I have to let off and let the truck build charge back up.

Now THERE is your payback from more batteries. Run the winch steady and save enough time that you can slow down to 55 MPH. Save from less idling, save your start batteries, save by driving slower both loaded and empty.

Your miles per day and hours of daylight are fixed. All downtime that you save can be used to drive slower.

[iamnotahippee]

So doing the math, my winch has a 1.5 hp motor, 1100 watts. The additional batteries will be a good addition at some point, but it still won't eliminate the need for idling. Can't afford to get stranded with a truck that won't start. I used to use a trailer that had much less winch on it, and its own battery, with no charging hooked up. We could get a couple good, solid 20-30' pulls, loading 2 buildings, before it was getting weak and needed a good round on the charger.

[freebeard]

Auxiliary Power Unit. The ones they had in B-17s were sweet. Honda?

[JRMichler]

Originally Posted by iamnotahippee

So doing the math, my winch has a 1.5 hp motor, 1100 watts.

One small deep cycle battery is rated at about 50 amp-hours. 1100 watts divided by 11 volts is 100 amps. Theoretically, one battery should run that winch for 1/2 hour, BUT no deep cycle battery will deliver 100 amps for very long.

Put in three such batteries, and each has to deliver only 33 amps. That should work much better. Connect them through an RV isolator as mentioned earlier. An RV isolator lets you work off the deep cycle batteries without pulling down the starting batteries. Then, when you start the engine, the isolator has the alternator recharge the deep cycles.

Your usage is drawing down your starter batteries. Starter batteries are designed to deliver large current for a couple of seconds, then get fully recharged. Deep cycle batteries are designed to deliver less current for a longer time.