Aerodynamic Suburban or GM SUV (92-99)

[aardvarcus]

ChopStix,
I appreciate your input but please don’t misunderstand as in this thread I am planning for my fourth heavily MPG modified vehicle, after getting the first three to 30-50% over baseline/EPA without special driving techniques (i.e. still using cruise control). If by my truck you are referring to my Tacoma that project has basically reached an impass as I am currently being limited by the rolling resistance of my oversized all terrain tires. To make additional significant gains without drastic measures I would need to go back to stock height and street tires. Not ready to do that yet as I do use the truck offroad regularly, and my previous method of having dedicated on-road and off-road tires ended up being a pain to switch out. The real problem is the Tacoma does not have enough room for my family, it works but it is uncomfortable. Thus I am trying to stop spending time/money on it which is why I started this thread about a different class of vehicle, 90s model GM SUVs.

On the wheel front, I may have figured out a solution to mount DZUS brackets to the PYO alloy wheels, just need to find some appropriately sized aluminum Z flashing to attach the DZUS spring to one end and the other end to the face of the wheel.

On the side view windows, the new fourth generation Prius has gone back to windows mounted to the A-panel unlike the third generation which mounted to the door. I would assume those mirrors have spent lots of time in a wind tunnel, and they do not appear to be excessively big or small.

[aardvarcus]

So I did some rough sketching of my ideas for a 90's model Suburban. Please note this is not daydreaming, I will be building this or something similar in the not too distant future, so please provide your ideas and feedback to improve the design.

The highlight is a chopped top over the rear cargo area with a grafted in aluminum faux bedcover. The majority of the bedcover would be permanently attached, with a smaller hatch opening in the rear portion. The bedcover would be bare aluminum to give the appearance of an Avalanche with cover.

Supporting this modification would be some taper worked into the existing roof, probably be grafting in a tapering roof section (cut a front roof panel near windshield turned backwards). Additionally replacing the rear cargo doors with a step side tailgate, and plan tapering the sides of the suburban to meet up with the narrower tailgate. The bedcover and bumper would taper to match.

Other modifications would be a full belly pan, side steps/belly pan/skids, aluminum front and rear bumpers, faux aerodynamic grill guard, conveyor belt tire spats/mudflaps, etcetera.

[rmay635703]

The most bang for the buck in a suburban is a diesel motor.

Both the 4.3, 5.7 and 6.2 (c-code) motor when put in with a manual transmission will give you the largest increase bone stock 2wd.

Converting it to a true FWD with a manual transaxle adds another 10-20%

So your starting point should be about 30mpg once the original platform is optimized mechanically.

If you don't mind super slow driving drop in a Kubota for up to 50mpg at low speeds.

Then underbelly, fender skirts and the rest after you get the lowest hanging fruit.

[freebeard]

The rear hatch is similar to a Dodge Magnum, which I like.

(cut a front roof panel near windshield turned backwards)

It will have too much crown and be too 'square'. You'd want a flat transition to the cap. Better to establish the cross section you want and then pie-cut the metal and pull it down and in.

[aerohead]

*Sketch looks good.
Here would be your 'maximum' for contour.It's from Buchheim et al. shared by Hucho.

I would recommend as 'much' wheel fairing as you can squeeze in under there

[Big Dave]

You see these things all the time these days on the superslab. If they didn’t work, truckers wouldn’t bother with them.

Semi Truck TrailerTail® Fuel Savings Technology | STEMCO

You’d have to do some sort of variation to make them easily folded down (for city driving) and deployed for road driving.

[freebeard]

Too fiddly. As you say, it could be automatically deployable:




http://ecomodder.com/forum/showthrea...tml#post516203

[aardvarcus]

Rmay,
I agree on the diesel motor, one of the nice things about the 90s suburban’s is a 6.5L diesel was a stock option (no diesel swap title issues). Right now I am leaning towards a new (AMG/GEP) 6.5L or an Isuzu 4BD1T backed up by a NV4500. The 6.5 is the easier “bolt in” swap, the Isuzu would be harder but it has been done and documented before. Because of the vehicle’s intended use 4x4 is necessary, but I hope to offset the added weight of the 4x4 system with weight savings elsewhere and I will swap the lower gears typically in the diesel 4x4s out (4.10->3.42). I think weight and gearing are 95+% of the penalty of the 4x4 over the 2wd when it isn’t engaged.

[aardvarcus]

Freebeard,
Very true on the windshield part not matching well to a hatch, I didn’t explain my thought very well. I was really just thinking of the gentle compound curve right before the roof transitions to the simple curved top profile. I thought it would be easier to steal a few inches of that compound curve profile to start the taper, and then tilt the roof panel back behind that to hit the profile I need at the bed transition. The pie cut could be an option though.

[aardvarcus]

Aerohead,
I was planning on following the AST-II top profile and the AST plan taper profile (4:1 aspect ratio?) you had previously shared, unless you think there is a reason to use a different profile on this vehicle.

Thanks for sharing the VW picture, that is very helpful for designing the tire fairings. I am a bit surprised by the size of the leading faring for the rear wheels. I am also surprised by how much wider the fairings are than the wheels/tires. This may be way too complicated, but I had considered using a “U” shaped aft tire fairing with an open back and ducting some engine bay air into the aft tire fairings to “fill the wake” once the fairing ended.