Aerodynamic Suburban or GM SUV (92-99)

[aardvarcus]

I got a spare 2000 era GM 8 lug 16” PYO alloy yesterday, along with a factory early 90s stainless wheel cover. The stainless wheel cover weighed 1.7 lbs, which isn’t too much but is about 10% of the weight of the wheel. Making pieces from 0.090 Aluminum would weight about the same.

The wheel cover would almost push into the alloy wheel, but the angled in nature of the “flat” part of the wheel kept it from going. It looked like I could bend the little tabs which grip the wheel in slightly and the wheel cover would go on the wheel, but I am a little wary of having it seated in the angled section, as it would seem prone to popping out. The only thing holding it in would be the tabs digging into the finish of the wheels, which I am not crazy about either (corrosion not looks).

This is making me think that I would have to use another attachment method, such as DZUS fasteners. DZUS fastened moon hub caps are available and I know racers who use DZUS wheel covers without issue, so I think I will try to find a way to remove the stock locking tabs and use DZUS fasteners to attach the OEM hubcap to the alloy wheel.

[ChopStix]

A guy used gorilla tape on this forum to help attach snap on moon hub caps. I don't know if that would help you or not. Just something that I read. He claimed "its like duct tape on steroids, and the caps are now a bear to remove".


I picked up a roll of urethane lawn edging in black. Some kinds have the L top. This kind has the full rounded loop top on the lawn edging. I'm going to use it to make a small nose spoiler that stops at the same level as my cross member. This will fill the roughly 1 inch difference between my bumper cover height and the cross member. But my plan is to make a nose pan that mounts to the loop of the lawn edging going back to the cross member. Then on the sides, I'll cut additional sections of the edging and bolt/glue them on as spats. I'm copying the 40mpg Ford Ranger shown on this forum, with a couple changes that better apply to my van. Then later on I'll buy a roll of the L type lawn edging to use as side ground effects.

Lastly I emailed the guy from the university of Michigan who wrote the tech article that I briefly mentioned before. I have not yet gotten a reply. But I want to make sure about what exactly that tech article contains before I spend the money to buy it since its suppose to be about aero mods for suv's and vans.

[aerohead]

Originally Posted by ChopStix

Oh I would certainly share any advise that I would get, and give credit where due. But I'm trying to refine what I'm trying to do first.

So three questions then.
How low should side skirts go?
How low should the spats go?
Lastly is it beneficial to angle the side skirts out towards the rear?

Ecomodding is addictive....its like the hotrod guy who keeps trying to go faster!

*I'd recommend that the skirts (rocker panel extensions) lower edge be even with the bottom of the belly pan.
*If by 'spats',you mean the little air deflectors which precede the wheels/hourglass openings,I think you'd have to refine them in a wind tunnel.
*As to the angle of the skirts,no angle would be fine,just vertical.

[freebeard]

This kind has the full rounded loop top on the lawn edging. I'm going to use it to make a small nose spoiler that stops at the same level as my cross member... But my plan is to make a nose pan that mounts to the loop of the lawn edging going back to the cross member.

I've never used lawn edging, but it seems to me that one could slip welding rod (pieced together tip to tip) or lead solder (sucked through with a vacuum cleaner?) into the edge. Welding rod would resist the air pressure and could be bent back to shape after any impact. Solder would add less stiffness and more weight. I'm not sure which (if either) would be worth it. Old coat hangers for the best ROI.

I'm curious how you will attach the front edge of the pan to the lawn edging.

[ChopStix]

Originally Posted by aerohead

*I'd recommend that the skirts (rocker panel extensions) lower edge be even with the bottom of the belly pan.
*If by 'spats',you mean the little air deflectors which precede the wheels/hourglass openings,I think you'd have to refine them in a wind tunnel.....

Originally Posted by freebeard

I'm curious how you will attach the front edge of the pan to the lawn edging.

Instead of typing a long drawn out explanation, I'll just post images of my plan being executed. Nothing that I'm doing is anything new. Its all taken directly from your advise and others posts on this forum. I'll start a new fuel log when done as well to track the results.

[aardvarcus]

So I have been looking at side-view mirror options for this era vehicle.

The stock chromed metal manual mirrors were common on 88-98 trucks. The mirror is about 9-1/2” x 6-5/8”, with a roughly 3” x 3/4” metal tube connecting it to a triangular base plate on the sail panel with a 1 3/4” bulge 4” tall. This is roughly 72 square inches total area. The mirror body is reasonably rounded on the front, but the overall design does not appear to be aerodynamically optimized.

Another stock mirror was the lower profile styled electric mirror. This mirror is about 9-3/4” x 5-5/8” with a 3 3/4” tall 2 1/2” long extension from the sail panel. This is about 64 square inches total. This design is also reasonably rounded in the front.

Other mirrors have been adapted to this era vehicle, anything that mounts through the sail panel shouldn’t be too hard to make work. Unfortunately most of the internet knowledge is about making oversized tow mirrors fit so that doesn’t directly correlate to what I am doing.

[aardvarcus]

Looking at a few options, I checked out a GMT-800 newer style mirror which I know has been swapped (with some work) onto this platform. This mirror is much more rounded in design, including the mount. This mirror is about 11” x 7-1/4” with a 3.5” tall 1” long extension, totalling 83 square inches. This mirror is very rounded, but the increase in frontal area probably doesn’t make this a good swap.

For another option, I checked out a second generation Toyota Tacoma mirror. This mirror is reasonably rounded, with a defined slope from middle to outside. This mirror is roughly 8 x 6 1/8” with a 1 1/2” x 2 1/4” neck. This mirror is 52 square inches. The lower frontal area and slightly improved design would make this an ok swap.

To get better designs and lower frontal area, I probably need to look at car (non truck/suv) designs. I am curious to hear some suggestions for stock-esque functional aerodynamic mirrors that mount through the sail panel.

[freebeard]

The problem with the sail panel is, aerodynamically, it's in the wrong place.


http://ecomodder.com/forum/showthread.php/trends-bus-aerodynamics-17717.html

[aerohead]

consider a unit who's housing is at least 80mm away from the side of the truck.
I'm suffering through right now with motorcycle mirrors just banged on with inappropriate mountings.

I've electrical taped fairings around the struts and tufting show laminar flow.The new supercars have examples of low drag mirror systems.

[ChopStix]

I made some progress in my bolt ons. But I didn't get any images yet. Plus it keeps raining every other day....

@aardvarcus, there are a few Ford Rangers on here that are worth checking out. They will give you ideas to consider for your truck. I'm mostly copying them on my van. Here's someone else's gallery, 40 to 60 mpg in a Ranger is pretty amazing. LINK