affordable Aero mods for LARGE SUV
 

What are some great inexpensive mod

i commute about 90 miles aday round trip.. and gas is 6.39 a gallon

Currently getting 25.5 avg (peak is about 27.5 on good days)6.0 V8 SUV over the last 10 fill ups which actually isn't too bad considering the situation

my Toyota corolla is getting 45mpg avg(peak was 50mpg) on the same route..


i rather much be in the SUV(due to the crazy drivers out there.) but have been taking the car 1-2 days a week to mitigate my fuel costs



one of the issues is the hybrid battery it's pretty much dead. 100%. P0A80 code..


i got the tyres pumped for 46PSI..

i was thinking something along the lines of a belly pan...

i may have found another alternate route the appears to have more down hill as well... Less twists and turns (that wastes a lot of fuel in it self)
i'm going to test it today


this mod also has to be able to withstand 85-90mph speed

Make it larger. Fineness ratio is your friend. Plus you can add crumple zone[s].

To paraphrase the racers, [economy] costs money, how [cheap] do you want to go?

Funkhoss' station wagon shows the way -- stack up the transmissions.

Finally giving up on all the BS?

I'm certainly not going to point any finger. I've still got more Beetles than Metros.

The Super get ~25MPG running on three cylinders, and the Baja is a roller.

It has a 4 speed(physical gears not imaginary ones) EVT transmission already

technically it's a 6 speed 2x CVT and 4x physical gears....

i can budget 800$ going from 25 to 40-50mpg would quickly pay me back in 4mo based on the current rate of fuel expenditure i spend on fuel...

There's more to getting that station wagon to 46MPG, side skirts and such.

You can put lipstick on a pig but that won't make it fly. ....or something. Do you have a plan?

The single biggest change you could make is a boat tail., but it's a pain in the aft. And it might get you to 30-35MPG.

This is a tough one.
How to get better fuel mileage in a:

• Full size SUV
• that needs to go 85mph to 90mph
• on a 90 mile per day route
• with fuel costs at $6.39 per gallon.

If I were to make that kind of question on this forum I would be told to move to another state where I can live right next to my job.

I'm going to venture out these opinions, take 'em or leave 'em.

The objective is to follow your priorities. I see that safety seems to be your top priority, which is the reason for choosing the SUV. As far as that goes, I would urge you to first research the safety of your vehicle vs. other, more fuel efficient models.

Just going by "it looks big so must be safe" makes about as much sense as "it looks small so must be fuel efficient." There's a chance the Tahoe isn't as safe as you think it is, and that some smaller, more fuel efficient car out there could actually be safer.

According to the NHTSA, the 2023 Chevy Tahoe only gets an overall 4 star crash test rating. Have you considered this? Does having less than 5 stars not mean anything to you?

The main killer of 5 stars is it's 3 star rollover rating. If you're traveling 90 miles a day, how much of that exposes you to front (4 to 5 stars) and side (5 star) impacts? I would guess you do a lot of high speed freeway driving, the kind of driving that exposes you to drivers clipping into a corner of your vehicle and sending you into a deadly rollover. Do you really want a vehicle with a 3 star rating for that kind of driving?

https://youtube.com/shorts/zRm-BSzhe...Cqgnbb4iRSRabj

Of course maybe I'm wrong. Maybe you drive along cross streets all day and need protection from side impacts.

On the other hand, the 2023 Prius and Prius Prime have G (Best) rated 2.0 side crash tests with the IIHS. The new 2.0 similates something as big and heavy as being T-boned by a large SUV or pickup. If the Prius does well in a side impact by a large SUV and doesn't have the rollover put-your-head-at-bumper-height problem, then what's holding you back????!!!!

https://www.youtube.com/watch?v=XZ7BrAPCpIM

I mean, seriously. You could be driving a Prius and be safer than you are now. Seriously!

www.summitracing.com/search/part-type/roll-bars-and-roll-cages/make/toyota/model/corolla

Six-point roll cages as low as $600. Put the rest in stance and anti-roll bars.

The "safety" claim is usually either made out of ignorance, or rationalization.

People who want to be 'safe' aren't overweight (80% of people are overweight). They exercise and mind their diet. They don't climb up on ladders. They minimize travel, especially at night and early morning, they don't take any drugs including smoking or alcohol...

"I have to drive a large tippy vehicle 90 MPH because safety" is a dumb take.

'mods'
 

I did a back-of-the-envelope calculation on the Tahoe, and relying strictly on aero, I don't see how you could have any probability of seeing above 36.6-mpg.
That's at Cd 0.12.
Without adding any length, and considering all the usual suspects, you might get to Cd 0.265.
Below that, you'd need elongation. Enough to get your wake down to about 14.5 square-feet, from about 32.0.
The 'transition zone', building into the ultimate slope angle would require 64.5-inches by itself, putting you at 266-inches, total length, from 202".
The Tahoe's squareback is your enemy. There's just no facility for meaningful drag reduction without boat-tailing, top, sides, and diffuser ( once you get one ).
You could probably pull it off with $800.00. Lots of time! Man-hours.
And then, dealing with over five feet of tail.

This is what I would have suggested, guessed too.

This is also why a lot of SUV manufacturers are starting to promote "coupé" SUV's, like the Tesla Model Y.

If they start making a coupé Tahoe, that would get you closer than adding a huge boat tail. You could still add a boat tail to a coupé SUV, only it could be made much smaller.

Square rear ends are terrible for aerodynamics. Try to shape the Tahoe into an Aptera as best as possible for best high speed fuel mileage.

' Coupe SUV '
 

Right!
The Audi E-tron is illustrative.
This SUV can be purchased with:
Cd 0.28 raked-back
Cd 0.26 Sportback
Cd 0.22 fastback GT
depending, essentially on which roofline one chooses.

What about the BMW X4? It may be smaller than a Tahoe, but it's still considered an SUV and is in the Coupe flavor. Just a quick glance, it costs about the same as the Tahoe but gets better fuel mileage. I'm not sure what the safety ratings are though.

' BMW X4'
 

There's one in Denton that I see at lunch, driving around the University of North Texas.
It's 'hideous' to me, and better looking in the photographs.
I don't have a 'blueprint' of it, so I can't evaluate it's roofline.
This may have been the car which got the guy who signed off on styling fired. BMW spent $ 260-million to 'fix' the design.
Personally, I prefer the fastback coupe design because of the aero. They're turbulent-quiet and laminar-loud. Raging calmness. But I understand that many buyers have expectations about 3-row seating and gobs of interior room.

is there a reason rooflines seem to be more important when tapering, verus tapering the sides? isnt closing the wake the same thing, whether horizontally or vertically?

I would agree. Didn't the EV1 have tapered sides too?

But as with anything, "does it look cool?" is the most important argument.

I really, really, really hope that Aptera takes off. Right now, the future seems to be an SUV invasion apocalypse.

well apparently narrowing the roofline has a bigger impact than the sides. doing both is obviously optimal

Out of curiousity I went looking for the Cd of thr BMW Isetta.

According to https://www.automobile-catalog.com/c...html#gsc.tab=0 its 0.60.

Too much of a good thing?

' important'
 

It's conditional.
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On a notchback, it cannot be predicted with the probability of fastbacks and squarebacks.
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On mass-produced fastbacks, the roofline is doing the lion's share of pressure recovery, while the sides cannot begin any meaningful section reduction until the rear wheels are passed.
Then, the same care as the roofline would have to be respected, to ensure that no super-deceleration and adverse pressure gradient were produced, otherwise, this 'boat-tailing' would provide no benefit.
Beyond the rear wheels, the added plan-view boat-tailing adds a synergetic benefit to pressure recovery.
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For an 'actual' squareback, where the top, sides, and bottom end at the same place on the body, the sides and diffuser shape would be of equal importance as the roofline. No surface would be allowed to be so 'steep', as to produce the adverse pressure gradient super-deceleration Hucho, and all others tell us to avoid like the plague.
Boat-tailing top and sides along a simple straight angle provides a 60% drag reduction benefit compared to just doing a straight, angled roofline. And if you don't radius the edges you lose 13% of the drag reduction potential.
You lose also if the diffuser isn't elongated ( let's wait until Jeff Howell conducts this research for these numbers, and let's wait until Jeff Howell conducts tests for tumblehome impact, and ditto for 'cambered' boat-tail surfaces all around ).
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For notchbacks, one would initially modify the aft-body into a 'fastback', then, afterwards, you would proceed as with a fastback.
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After another 3-generations of boat-tailing investigations, Jeff Howell et al. will have caught up to the aerodynamic state-of-the-art for boat-tails, as of 1986.
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The trick is to reconstruct the 'entire' longtail vehicle from it's blueprint ( photographs cannot provide the dimensional information we need ), top, sides, and bottom, all the way to it's farthest extremity; then, when elongating 'ANY' surface of the body, you stay along this imaginary contour suggested by the longtail blueprint you've created.
Hucho has used 'contour comparison' for this type of exercise.
It's why it's so important that everyone know how to draft and be able to perform scale measurements, or CAD, AUTOCAD, etc..
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Once you 'know' where 'the rest' of the vehicle would be, streamlining becomes 'modular'. 'Plug-and-play.
Just pick a 'length' you think you can live with, then simply elongate the body out to that length, along the imaginary contour you drew.
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Drag reduction will be a function of the reduction of wake area, compared to the OEM wake area.
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' EV1 taper'
 

yes, GM provided a plan-view photograph of Impact/EV1 # 15 in their wind tunnel.
careful examination of this image indicates that the body plan-taper initiates at about 12-inches ( 305mm ) downstream of the side mirrors, forming an uninterrupted geometric contour, of reducing cross-section for the rest of the body length. Cd 0.197 was the official Cd according to GM.
Cd 0.137, with the 'Yellow Ferret', 1-meter, aluminum boat-tail, at Fort Stockton, Texas, Firestone Proving Grounds, 1993.
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AeroStealth attended the big BEV car show in San Diego, California this summer, and said that the Aptera display was so swamped that he couldn't ever get close to it, the whole weekend.

I mean he has a point. Just law of dynamics whoever is heavier will always be the one who will probably come out better. A 4 star crash rated Tahoe will whoop a 5 star crash rated priuses ass. I would hate to see what a hummer EV would do to a prius at over 3x the curb weight.
Pointless safety aside, you're averaging 25mpg driving how fast? 85-90mph in the prius average speed is maybe 31-34mpg.
I will say I bumped the FE on my Sequoia up with a sheet of coroplast going from the front bumper to just behind the driver door for about $35. 4x8 sheet and some holes and a slight trim around the wheels. Averaging about 20mpg on my commute consisting of 25-65mph roads 14 miles to work. At least ever since it got cold, it may have been higher two weeks ago.

"Will always... probably?" That's always probably right!

If the collision is head-on or a side impact (T-bone) then yes, the Tahoe is always probably going to be better off.

If the accident is a single vehicle or a bunch of vehicle traveling in the same direction, then I'd say the Tahoe is at a disadvantage due to a higher probability of rollover, unless we're talking about a car pileup, in which case the safest car is the one that isn't in front of any 18-wheelers.

Anywho, I do notice that my fuel mileage drops a lot in my Toyota Avalon hybrid from going above 65mph. For this reason I try not to go over 65mph. I have done 80mph and I seemed to get around 35mpg instead of 40mpg.

' not over 65 mph '
 

A perfect example of the velocity-cubed power law eating your wallet or debit card.;)

Another reason to doubt the safety of large SUV's.

We're now at the 10th person who has been ran over by an SUV or pickup in the neighborhood since I moved here in 2011. 5 of them died from the accident. People keep running over other people, including their own kids.

Doing some research it was a lot safer to be a pedestrian back in 2009. Your chances of being ran over as a pedestrian back then was 1.3 in 100,000. Now it's up to 2.2 (at least it was in 2021, if the trend has continued it is now higher.) https://www.iihs.org/topics/fatality...il/pedestrians

The reason why more people are getting ran over is that SUV's and pickups have become more popular. Statistically you are 80% more likely to run over someone walking along the road in a Pickup, and 61% more likely in an SUV, than in a car. https://www.iihs.org/news/detail/suv...-while-turning

I checked Wiki, is this:

In 2008, a two mode hybrid was offered with two trim levels, HY1 or HY2. A 332 hp (248 kW) 6.0L Vortec 6000 with a pair of 80-hp, 184 ft.-lb. torque electric motors was offered. It had a 0.36 to 0.34 drag coefficient from upgraded body panels and a 12V/300V battery system. The hybrid models also included 300V Electric AC, 42V power steering, and LED taillights (only an option from 2008 to 2013).

I also found an interesting description in Wiki:
https://en.wikipedia.org/wiki/Global_Hybrid_Cooperation

It uses 2 or 3 planetary gearsets in an automatic transmission: one on the internal combustion engine (ICE) side (input split) paired with a second (output split), forming the compound split, and possibly one third additional planetary gearset to multiply the number of fixed gear ratios (up to 4).

Is this the "2WD" version?

Limiting to just "aerodynamic" modifications risks "polishing the musket balls." I prefer tuning the whole vehicle. Regardless, can you share front, side, underbody, and top photos?

• front - evaluate cooling air inlet and air flow
• side - the wheels and wheel covers
• underbody - how draggy that side looks
• top - looking for drag sources

It helps if you have tools needed for any tuning:

• What vehicle instrumentation do you have and are willing to use?
• Do you have a video camera to investigate air flow?

What is your improvement expectation, when we can stop?

Redundant but I prefer to tune the whole system, not limited to just aerodynamics. Aerodynamic tuning can not overcome other low hanging fruit.

If you decide to do whole vehicle tuning, it may make more sense to start a fresh thread under "Hybrid" for a hybrid Tahoe.

Bob Wilson

It looks like @Tahoe_Hybrid drives 90 miles a day and buys a new Tahoe every year. @Tahoe_Hybrid has (or had) a 2020, a 2021, a 2022 and a 2023 Tahoe, according to the stats section.

Of course, if that's the case, either ecommoding would need to be done every year to a new Tahoe, or we need to figure out a mod that can be interchanged between Tahoe years. Maybe a detachable boat tail. :confused: