Creepy White Van - E150 Build

[Merlyn2220]

<Snip> Moved to Aerodynamics forum.

[Merlyn2220]

This week I installed Hellwig 7008 1.375" front and 7183 1.25" rear anti-roll bars. The recommended part numbers for the E150 are the 1.125" 7604 front and the 7642 1.125" rear bar. Given the pig-heavy front end, I wanted a significantly stiffer than stock front bar. The 1.375" is 50% stiffer than the 1.125", so that fit the bill. My only other rear option was a whopping 1.5" bar, which is 75% stiffer than 1.125", and 20% stiffer than my 1.375" front choice. With a stiffer rear bar I'd run a risk of terminal oversteer, especially if I end up with stiffer rear springs to handle a large towing load. So I stuck with the 1.375" front and 1.25" rear.

(And yes, I know that the differing widths of mounting points makes a significant difference in roll stiffness. Before buying I could only make a rough judgement as to how they differ, and I sure wasn't going to buy and return and buy again!)

Here's the front:


And the rear:

[ChopStix]

On my old Astro van the rear bumper scooped a ton of air on the lower edge. So you might try making a belly pan across the rear of the van to prevent this from happening on yours. I always thought that I could have gotten 1 or 2 more mpg from one. But an Astro is different than one of these Ford creeper vans, as Astro's are more like a car than a truck.

[ChopStix]

In reply to my previous post. The back end air scooping effect is why its been said numerous times on this forum that a slight hotrod rake improves mpg on brick shaped vehicles. But a slight rake is hard to keep on work vans, as they are constantly overloaded and sagging the back end.

[Merlyn2220]

That's a good point on the bumper "scoop" sticking down into the airflow. I've made it worse now with the hitch, but it's a necessary evil. I considered using the gap between the horizontal bar on the hitch and the bumper's lower lip as a diffuser slot. I'm not sure it's really big enough to do anything, but when I get to the rear section bellypan I'll have to experiment with it.

So far the ~12 degree departure angle seems to be at least as good as the previous taper. From what I've read, no one really knows the optimum departure angle for a "short tail" so I'm just copying what other major manufacturers have done.

[Merlyn2220]

And very odd but interesting results from last tank. 2 tanks with a 20-30 degree departure angle taper at 14.44 and 14.31mpg. This one with a supposedly better 12 degree angle...13.79mpg. So I'm leaving it alone and running another full tank to be sure the result isn't a fluke.

The only other thing I changed between the 2 tanks and the latest, is that I increased the tire pressures from 35/45 to 50/60 F/R. I can't see FE being worse with higher pressure, in general. But I know that on bicycles there is a point of inversion, where the rolling resistance starts increasing above around 130-140psi. So it's unlikely but possible. If the next tank is also ~13.8 I might drop the tires back down to confirm that there's no substantial difference.

[ChopStix]

I can't advise on your truck tires, but I ran 50 psi on my LRR tires, which is above the side wall psi rating.

Also you can't truly judge mpg based on 1 tank of gas. Me, I don't believe any mpg change until I have 10 refills on it. Then I average the measured to show positive change over time.

[Merlyn2220]

I went through and moved the aerodynamic portion of the thread over to the Aerodynamics Forum. I'll post engine/transmission/suspension improvements here.

ChopStix I realized the other change that I made last week...I fixed the A/C!!! It was tolerable in the spring with 80-85F temps and the windows down ~1 inch for a little airflow, but when it got into the 90s I had to break down and repair the leaky high side valve, vacuum and refill. I started using the A/C last week, and it's definitely a power hog on the highway. I have no idea how much, but my vacuum gauge is showing around 8-9inHg instead of 9-11inHg on a drafting cruise. I think it's time for me to finally build the MPGUINO!

[cRiPpLe_rOoStEr]

Originally Posted by Merlyn2220

I started using the A/C last week, and it's definitely a power hog on the highway. I have no idea how much, but my vacuum gauge is showing around 8-9inHg instead of 9-11inHg on a drafting cruise.

Have you never considered to adapt an all-electric air conditioner, or to replace the stock compressor with a 12-volt one similar to the ones used for motorhome and trailer appliances?

[Merlyn2220]

I ran another tank, trying to use the A/C about the same amount as the last one. MPG ended up at 12.92, compared to 13.79 the last week. This is substantially lower than before the 12 degree mod @ 14.31/14.44 for 2 ~32 gallon tankfuls.

I hadn't thought about replacing the A/C system, but I don't really use it all that much. That's either a good argument for not bothering to fix it, or that replacing it with a smaller unit would be perfectly acceptable. Conventional wisdom is that the AC compressor uses around 8hp, and is about the equivalent of a 1.5-2 ton system. At around 20,000BTU/hr that's an electric equivalent of 1500-2500 watts, or 2-3.3hp. I could probably get away with an effective A/C about 1/4 that size, since I rarely put it over "low" on the fan except in the middle of summer. Even at 100% efficiency, an electric one would need to be good for 375-625 watts, or up to ~45A. The 12V car compressors are good for around 300-400BTU/hr, which is 1/50th as big as the stock car system. Unless I'm missing something, I don't see how this could work.