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Old 04-26-2017, 06:40 PM   #1 (permalink)
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aero mods for traverse/acadia/outlook/enclave?

Ok, I used to be on here under a different screen name, but can't access that email, anymore. I successfully aeromodded my Saturn ion back in 2010, and it made some big refinement improvements (a lot less wind noise) and some fuel consumption improvement. As my screen name suggests, I've sold my Saturn because I have a growing family, and the Saturn and jetta we had were both far too small for our needs. We sold both and decided on a 2017 gmc acadia, which matches the Jetta's fuel economy without too much effort. The model we got lacks active grill shutters offered with the 4 cylinder, but refinement isn't needed, as the denali has so much sound insulation it's ridiculous. The visible part of the body is very nice and smooth, with seals between every panel, and it gets 35MPG indicated at 55MPH, but my area has just announced increased speed limits, so I would like to bolster this as much as possible. Has anyone looked closely at the older traverse/enclave/acadia/outlook or the new acadia? the only thing I can think of is some kind of manual grill shutter (any easily adoptable designs that work well?) or some kind of underbody cladding. Will any of this even make a difference with how low the front air dam is compared to the underside of the car? It's around 4 inches lower as far as I can tell.

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Old 04-27-2017, 05:22 AM   #2 (permalink)
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Higher average speed = taller gearing. The ROI to change overalll ratio is in changing the tire size. What do you have currently? You can probably go narrower on the same rim, but eventually, like the BMW i3, you go to a bigger wheel diameter to go taller and narrower.


GMC Acadia Forum: The black metal bar under the vehicle

Is it this shiny?
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Old 04-27-2017, 10:32 AM   #3 (permalink)
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I personally just don't understand SUVs unless you plan on going off road. The 2017 Acadia has 1 cubic ft more cargo space than my wife's 2012 Civic, both have the same number of seats and plenty of leg room... I just don't get the appeal.

Well enough of that rant... To answer your question, yes. A grill block will help your gas mileage, by allowing your car to get to normal operating temps faster and also improve aerodynamics on the highway. A smooth underbelly will help a lot as well, though those are starting to come on many factory cars now in order to help meet EPA standards. Check out what it looks like under there first, if it's clunky and rough (like the pic Freebeard posted) then a belly pan will definitely help.
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Old 04-27-2017, 10:33 AM   #4 (permalink)
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I have 235/55/20s right now, about as tall as I want to go, as I imagine they're already pretty heavy. the tires are well regarded, and low rolling resistance michellins, so changing tires on a brand new car to get taller tires (and paying for an ECU reflash) isn't practical for me. it would also complicate the already not easy task of finding 17 or 18 inch rimmed winter tires. the width of the tires is well matched to the width of the rims.

the grille is the denali design

can't post an image, yet

which has some built in blocking at the grill due to the design, but for it's massive size, only 24x7 of that is actual radiator real estate, and the only blocking they did at the factory is 3-4 inches behind the grill. the lower grill is blocked to the size of the radiator, and I'm leaving it alone except maybe for winter.

I'm considering spray on vinyl wrapping the grill, otherwise with the chrome I don't know how I could attach the block and have it look even remotely good.

I've seen that picture, and finally climbed under this monster today, and between the V6, dual(ish) exhaust, and AWD gear, there isn't much area that isn't hot or moving. if I had the equipment and money, a nice sheet of aluminum could make it as smooth as the bottom of my Saturn, or the new cruzes, but in coroplast, I think my options are limited to the 8 inches outside the frame members that run the length of the car.

So, given this info, I wonder if all this work is even worth it given how little area I can effect? Basically, from the 500 miles I've spent driving this thing so far, the best gains are achieved by keeping it in cylinder deactivaion and high gear, so my goal was to make this easier with less drag. luckily, it's geared pretty high, so revs stay low enough, I'm not worried about that.

And I'm so glad I didn't get the 4 cylinder, it can't tow (which I need), but we borrowed one the other day, and in stop and go, the transmission got up to 200 degrees, and because it doesn't get the tow package, you don't get a trans cooler, so it didn't cool down until many miles later at highway speed.
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Old 04-27-2017, 10:45 AM   #5 (permalink)
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Quote:
Originally Posted by Shortie771 View Post
I personally just don't understand SUVs unless you plan on going off road. The 2017 Acadia has 1 cubic ft more cargo space than my wife's 2012 Civic, both have the same number of seats and plenty of leg room... I just don't get the appeal.

Well enough of that rant... To answer your question, yes. A grill block will help your gas mileage, by allowing your car to get to normal operating temps faster and also improve aerodynamics on the highway. A smooth underbelly will help a lot as well, though those are starting to come on many factory cars now in order to help meet EPA standards. Check out what it looks like under there first, if it's clunky and rough (like the pic Freebeard posted) then a belly pan will definitely help.
Your wife's civic has 6 seats? we got it because we have 2 kids and one big dog and one little dog we carry around routinely, and with the third row down, there's a lot of room to do this. then when we go out of town to visit family in the hospital (seems to happen at least twice a year), or if grandma wants to come on a trip with us, or so I can feed baby in the back seat so we don't have to stop for half an hour at a rest stop (happens all the time in a car), we have the extra seats in the back so we can do that. I can also sit in all 6 seats with just a little shifting of the seats, and there's no way you have this much leg room and cargo room in a civic, I had a jetta that was the same size as your civic. We considered a mini van, but don't like the Toyota, the new Honda isn't out, yet, we don't trust a Chrysler, and all the others' safety ratings are spotty. Trust me, this was my LAST choice, but realistically it's the minimum we could both justify for our family's needs. also, with this generation of van, you can't get AWD unless you get a Toyota, and we need AWD in our town so my wife can get to work at any time of the day, she's an EMT.

plus, 35MPG on the highway and 20 in town indicated (yes, I still need to verify this) isn't bad, it's all our jetta could manage in a much smaller car.
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Old 04-27-2017, 11:12 AM   #6 (permalink)
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At least you out much more thought into your purchase than most people. I wasn't trying to be rude or insulting. I do apologise if it seemed that way. I just personally have never had I scenario where I have thought "I NEED an SUV", but we do live very different lives. I'll admit, I did forget about the third row seating in the Acadia, for some reason I was thinking it sat 5. The cargo space eating is only 1 cubic foot bigger than the Civic, but now that I'm looking at it I assume the rated cargo space is with the third row seating in place. There would be twice as much room if it were folded down. As for leg room, I don't doubt that the Acadia has more. I was just saying that the Civic has plenty to sit comfortably.

35 mpg is a nice number for something of its size and shape. It must have excellent gearing, as you have mentioned. Please do confirm your mpg on your next tank I'm very curious how it turns out. I use an MPGuino in my car which I've calibrated to be very accurate, but my wife's car came with a factory mpg gauge which is spotty at best. Sometimes it will say she's getting 39mpg, but at the pump she calculates 41mpg. Other times it will say she's getting 40 and it will be 37 at the pump. I'm still not sure how it gets it's numbers.

As far as increasing your mpg through aerodynamics... I believe you have a tough road ahead of you. I'm really not sure there is much, if anything you can do (aside from a grill block) without negatively altering the appearance of your vehicle.
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Last edited by Shortie771; 04-27-2017 at 11:18 AM..
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Old 04-27-2017, 11:28 AM   #7 (permalink)
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I used to be in the same camp as you, and never even considered an SUV until I started looking at, and actually driving the alternatives, and then talking to people that have both AWD SUVs (equinox) and fwd vans. The crash ratings and not so great MPG figures just sealed the deal for me. Right now I'm working with GM, as I can't fill up my brand new car, so once I get that fixed, I'll be able to verify the accuracy of the DIC.
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Old 04-27-2017, 12:08 PM   #8 (permalink)
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Just a side note, the Enclave, Arcadia, and whatever the Chevy is called all get the same epa rating but that is only because of a loophole that allows GM to not compete with itself. They get to just test one and call the others the same even though they clearly each have different aerodynamics. Same thing with the Ford Flex and it's very different Lincoln brother. I personally think the Enclave has more built in aero that at best you would be trying to march with the Arcadia bit that's too late now.

Edit, I see I'm wrong as far as 2017 is concerned. They just redesigned the Arcadia where you would have to wait till 2018 for the to-do of the Enclave. Assuming no first year growing pains the Arcadia is clearly better for 2017.

Last edited by Hersbird; 04-27-2017 at 12:46 PM..
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Old 04-27-2017, 01:02 PM   #9 (permalink)
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yeah, for 2017 the acadia is all new, a half-breed breed between the outgoing model and the equinox, while the traverse actually grows for 2018. oddly enough, it sure is an all new platform, but the underside is just as cluttered, and the outside area looks the same as that pic of the flipped over enclave.
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Old 04-27-2017, 02:18 PM   #10 (permalink)
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Maybe we've exhausted the 'SUV bad' topic?

There isn't going to be a lot of 'low hanging fruit' on a 2017 model. If you [properly] don't care about appearances you could make a vinyl mask for the grille with a zipper down the middle so you can open and close it, like the big-rig trucks used to do. (I don't remember seeing that lately.)

So it looks like the 'low hanging fruit' is underneath. (ba-dum. tish!)

The scope of the design problem encompasses serviceability (the underside of my car is like the dark side of the moon) and robustness, as in ground strikes.

Ideal would be a one-piece with dimpled recesses for the fasteners. 90% might be only partial pans covering only the bigger cavities and voids. Here's something for inspiration:



The Underbody (flat belly pan is suboptimal - explanation & solutions offered)

This thread was started by MTrenk (Formula SAE Engineer) in 2012-09 and runs to 16 pages. Maybe something of use in there?

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