Creepy White Van - E150 aerodynamics

[Isoldmysaturn:(]

that t100 underpan is ideal, but if that isn't realistic, you can always go from one protrusion to the next, or go to and around a fuel tank, for example, if it's on he same level as the pan. yes, you have to at least go front end to engine, then suspension to suspension, then suspension to rear end to achieve the overall goal.

incomplete aero treatments create turbulence behind the unfinished edge, and this adds drag, which unfortunately makes this an all or nothing deal. This is why people mock up in cardboard to prove concepts.

[Merlyn2220]

Originally Posted by BamZipPow

Take a peek at my belly pan thread.
http://ecomodder.com/forum/showthrea...pan-22621.html

How do you deal with the axle and driveshaft droop under full bounce? The E150 axle and driveshaft will drop waaaaaay down below the level of any reasonable bellypan. My plan is currently to leave the driveshaft area open, and attach a bottom plate to the axle, inside the springs. This way at the default unloaded condition it will be even with the rest of the pan, and when heavily loaded it will be above the pan. I'll probably put a front curve and vertical riser on it, so if I hit bumps it isn't a flat sheet hanging out in the airflow. Hopefully that makes sense.

Regarding the A/C, I talked with a guy at work who has a similar year F150. In his truck the A/C compressor runs pretty much continuously when the AC is "on" and he loses 1-2mpg (from ~17 to ~15) when using the AC. He manually cycles the AC from on to "recirculate" because otherwise it is so ice cold it freezes him out. Maybe he has a bad switch or something, I'll have to make sure mine doesn't do the same thing!

[BamZipPow]

Originally Posted by Merlyn2220

How do you deal with the axle and driveshaft droop under full bounce? The E150 axle and driveshaft will drop waaaaaay down below the level of any reasonable bellypan. My plan is currently to leave the driveshaft area open, and attach a bottom plate to the axle, inside the springs. This way at the default unloaded condition it will be even with the rest of the pan, and when heavily loaded it will be above the pan. I'll probably put a front curve and vertical riser on it, so if I hit bumps it isn't a flat sheet hanging out in the airflow. Hopefully that makes sense.

I have two crossbeams that section the bottom of the truck into 3 main areas. Engine bay, main, and rear. The crossbeams also provide attachment points fer my side skirts. The rear section is hinged at the front, middle, and rear to allow fer articulation. The rear hinge is a double hinge and allows lateral movement of the rear diffuser. Multiple rubber cords keeps the rear belly pan tight to the rear axle. As the rear axle moves up/down, the rear belly pan and diffuser will move with the axle. It took me a few tries to git the hardware configuration just right. Hope my work will help you in yer quest.

post #525437

[Isoldmysaturn:(]

This t100 bellypan is obviously ideal, but yes, you have to at least go between obstacles. Ideally, between the front end to the front suspension, front suspension to rear suspension, and rear suspension to rear bumper. You can always male access holes to facilitate engine and transmission servicing. At least the front part of the exhaust is either shielded, covered by aluminum like the t-100, or cut out. Just remember to keep it all as light as possible. Incomplete aero mods create turbulence, which adds drag, it's an all or nothing type deal. This is why a lot of people mock up on cardboard to test.

[Merlyn2220]

Originally Posted by BamZipPow

I have two crossbeams that section the bottom of the truck into 3 main areas. Engine bay, main, and rear. The crossbeams also provide attachment points fer my side skirts. The rear section is hinged at the front, middle, and rear to allow fer articulation. The rear hinge is a double hinge and allows lateral movement of the rear diffuser. Multiple rubber cords keeps the rear belly pan tight to the rear axle. As the rear axle moves up/down, the rear belly pan and diffuser will move with the axle. It took me a few tries to git the hardware configuration just right.

Ah, ok I see the new design now. I had looked at your thread last summer, but you hadn't built the diamond plate version yet. It looks to me like your center section (axle-to-axle area) is fixed, and the rear articulation all happens from the fixed hinge points about 12-18" forward of the rear axle. Is that correct? Because you are working on rubber spring tension holding the pan up, and a sliding interface (rubber pad under the shock perches) you don't have to worry about the axle going down too far and ripping off the front hinges. My thought was to fix the axle pan in place tight to the axle (probably with big u-bolts), and then figure out some flexible flapper sheet to go from the front fixed part to the mobile axle part. That might be more complicated than what you have, or more prone to squeaks. I'll have to think about that before building.

Per Isoldmysaturn's comments, did you find poor FE while you were rebuilding the pan? I'm hesitant to spend $300 on aluminum sheet to build the passenger side (muffler side) bellypan with questionable ROI.

[Merlyn2220]

Originally Posted by Isoldmysaturn:(

You can always make access holes to facilitate engine and transmission servicing. At least the front part of the exhaust is either shielded, covered by aluminum like the t-100, or cut out. Just remember to keep it all as light as possible. Incomplete aero mods create turbulence, which adds drag, it's an all or nothing type deal. This is why a lot of people mock up on cardboard to test.

I was planning on leaving the header side of the engine open, since it's at the front and on the passenger side (inline 6 engine). That will allow airflow around the headers, H-pipe connector, resonator and catalytic. Then from cat-back make an aluminum sheet similar to the T100's diamond plate setup. The stock catalytic is known for needing a separate air source (thus the ridiculous air pump setup). I'll have to research and see if the reason was to keep it cool(er), or to reduce the AFR that the catalytic sees.

The air going through the radiator has to go somewhere, so my initial plan is to leave the back side of the engine and tranny open to the bottom, with plates that smooth the airflow down around the body. The driver's side (no headers) is easy and already done. But I can guarantee that blocking off airflow around a hugely lossy C6 transmission is a bad idea. A C6 dissipates a LOT of heat, probably 10x as much as the T100 tranny. If I install a separate transmission cooler then I wouldn't be as concerned, but the stock setup is just a cooler built into the bottom of the radiator...and it's more of a fluid heater than it is a fluid cooler...

[BamZipPow]

Originally Posted by Merlyn2220

Ah, ok I see the new design now. I had looked at your thread last summer, but you hadn't built the diamond plate version yet. It looks to me like your center section (axle-to-axle area) is fixed, and the rear articulation all happens from the fixed hinge points about 12-18" forward of the rear axle. Is that correct? Because you are working on rubber spring tension holding the pan up, and a sliding interface (rubber pad under the shock perches) you don't have to worry about the axle going down too far and ripping off the front hinges. My thought was to fix the axle pan in place tight to the axle (probably with big u-bolts), and then figure out some flexible flapper sheet to go from the front fixed part to the mobile axle part. That might be more complicated than what you have, or more prone to squeaks. I'll have to think about that before building.

Per Isoldmysaturn's comments, did you find poor FE while you were rebuilding the pan? I'm hesitant to spend $300 on aluminum sheet to build the passenger side (muffler side) bellypan with questionable ROI.

Yes, the center (main) belly pan is fixed in between the crossbeams. There wasn't a requirement fer it to move.

The front hinges are about 3' in front of the rear axle just because that's where the attachment points fer the rear crossbeam ended up. The rear belly pan (rear crossbeam to rear axle) is about 4' in length and just extends past the rear of rear axle. This allowed me to attach the straps to the rear belly pan without any interference from the rear axle. My original design had the belly pan attached directly to the rear axle but my observations showed that the attachment angle was changing due to the flexing and articulation of the leaf springs. Since the belly pan isn't on the same plane as the leaf springs pivot, my original attachment point was gitting beat up. Even with the next version, the straps were breaking due to the stress as they were wrapped abound the axle housing. This is why I went with the current version so the attachment points won't git beat up since they are not tied directly to the rear axle and the belly pan is allowed to slide depending on the position of the rear axle. My current design is my best one yet to address all the various issues I had with the previous versions. The current version also allows fer easy removal of all components fer access and maintenance.

If you have access to free or really low cost Coroplast sheets, that would be a good medium to work with as long as you used some good bracing. Luan sheets are also low cost but has a tendency to delaminate after about a year depending on how much weather you expose it to. FRP sheets are definitely out of the question because of the cost, durability, and weight factors.

[Merlyn2220]

I tried to use the A/C about the same amount, and this tank was 13.92. The last one with the A/C fixed I used it for about 2/3 of the tank and got 13.79. So I'm fairly comfortable with it being around 13.85mpg, give or take a bit. I'm going to do the next tank without A/C and see where it stands.

BamZipPow thanks for the detailed explanation on your different versions! I've used Coroplast in several spots, but generally don't like it much. HDR (Home Depot Racing) has it for about $15 a sheet, but I'd prefer using FRP and foam board for it's high strength/stiffness and ease of gluing. I can't really use luan or cardboard because it rains here almost every single day from April->October. So even my prototypes have to be waterproof, and I tend to use aluminum and stainless if at all possible. I don't have to worry about salt on the roads here in FL, but rust and water ingress is still a big problem.

BTW - if you haven't tried them yet, you should look into rivnuts for some of your bolted assemblies. You can get the ABN rivnut tool for about $20, and then install real 1/4-20 nuts for less than $0.50 each in stainless or $0.20ea in zinc plated.

[aerohead]

I used them on the CRX belly and a few got loose and would just spin when attempting disassembly.A nightmare!
I'll probably use them again,but may install them coated with JB Weld to better anchor them.

[Merlyn2220]

So I started hacking off some of the rear of the shell, in an attempt to figure out what was going on with the cavity and taper. I removed the center upper section (with taper) at about 100 miles into a tank, and ended up with 14.27mpg. With the 12 degree side taper and upper section and A/C use I was around 13.9-13.9mpg. So the center was a definite negative, even with a reasonable taper.

At 240 miles into the next tank, I hacked off the sides to be ~4" long, following the general shape of the body from a side view. 15.24mpg is a dramatic improvement over the previous tanks. HOWEVER....part of that is because I was having overheating problems and not running the A/C much, and driving slow to keep the highway temps down. This followed up with 15.67mpg for the next tank, with no other aero changes. I'd attribute the extra 0.5mpg to mostly driving well under 70mph on the highway while I swapped parts (thermostat, pump, hoses and radiator) and it seems to be back to normal. So this tank should tell me what real impact there is from hacking off my abomination of a tail!