Exterior MPG modifications

[MyLonewolf25]

Here's something I did on paint, extended spoiler and rear skirt. This isn't my car, but it's the same color. If anyone is good at photoshop please help me out with this or some ideas, thanks.

In Texas, we legally only need one side view mirror. I'm thinking about having a plastic blockoff made that gets rid of the passenger side mirror, while still keeping a nice stock look. If one cared, they could mount a backup camera in this plastic blockoff, going to a small LCD inside, if that was one's choice.

Also, is a top grill block off a terrible idea on the 1.4 turbo? In the heat/summer?

Please share any other exterior mods that wouldn't make the car look too spacey but possibly shave some mpg. On the list of these types of gas saving mods are things like slight lowering from stock, and a shark fin antenna.

I don't really care how much these things cost vs. how much spending on fuel. This is just for fun ideas on exterior modifications.

Any guess what type of highway mpg's these mods would save? 1-2 mpg is my guess.

Fully smooth under tray
Low as possible
Extend the rear spoiler and arc it down
Grill blocks
Smooth out air transitions ( make a curved clear plastic cover that goes from the top of the roofline to the farthest point on the hood and extending back to the a pillars on the sides
Super tall skinny tires
Etc


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[MyLonewolf25]

I could basically make a .pdf diagram with all the measurements and drill points. I don't think any 3d printing services can make something that big but maybe a plastics manufacturer could. The .pdf would just be a reference sheet that tells people where to cut, where to drill, etc.

Why not just do a cad at that point?
You can also put those into sims for aerodynamics

Look up Kyle drives on YouTube
He's a race car engineer and has a video on great free programs for this kind of thing


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[2014 Blue RS]

For road trips, those rear wheel covers might a thing is try. Wouldn't like the look but I'd get used to it if it works.

 

[MyLonewolf25]

For road trips, those rear wheel covers might a thing is try. Wouldn't like the look but I'd get used to it if it works.

It would only help so much because it's not getting rid of a lot of high pressure in the wheel wells from it with no evacuation from trapped air

Also the closer to the the wheels and ground the better
Especially at the leading edge of the tire


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[Llia]

What about using a plumb-bob? Drive over a big sheet of paper and mark the mounting holes for the underbelly where the point is above the paper. Also use it to mark cut outs.

Lay the paper template over some aluminum and then cut the shape. Leave some extra material along the edges so you can roll/fold it over for strength and so it wont cut your fingers.

 

[MyLonewolf25]

What about using a plumb-bob? Drive over a big sheet of paper and mark the mounting holes for the underbelly where the point is above the paper. Also use it to mark cut outs.



Lay the paper template over some aluminum and then cut the shape. Leave some extra material along the edges so you can roll/fold it over for strength and so it wont cut your fingers.

That COULD work
But I'd only use it for a template for something out of fiber glass or carbon fiber

Weight is huge in economy
So is drag

No real use if you're adding a good 50+ lb for a untested aerodynamic part unless it's been designed under simulation

Unless you're building a skid plate
Even then depending on where Kevlar composite works better per lb


But me personally
Take the time
Make a well drawn up cad
Test
Change
Test
Change
Test
Change
Etc

You can feasibly do any of these eco mods for it and see how much drag changes

Weight would be slightly harder to work out but it should be hard to work out volumes of parts and just go off density from there

Shouldn't be too hard to extract theoretical mpg either
A bunch of math
But still
What well thought out part doesn't include this...
I can't think of any


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[mja]

Lonewolf -

We do have other threads about weight reduction, feel free to check em out.

 

[mja]

What about using a plumb-bob? Drive over a big sheet of paper and mark the mounting holes for the underbelly where the point is above the paper. Also use it to mark cut outs.

Lay the paper template over some aluminum and then cut the shape. Leave some extra material along the edges so you can roll/fold it over for strength and so it wont cut your fingers.

That's a good idea for setting the holes. What people aren't considering is the 3 dimensional structure of the underbody, its not an entirely flat surface.

At least the drivers side cruze underbody tray fits well enough that I'm not worried about it. The passenger side I'll redo at some point later.

 

[MyLonewolf25]

Lonewolf -



We do have other threads about weight reduction, feel free to check em out.

I have

I mostly looked at them to see how much sound deadening was in the car
Pleasantly surprised on how little

But I still stick by doing it in a cad program and then testing it
Because you can potentially add more drag by doing it incorrectly



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[HotBoxer]

Because you can potentially add more drag by doing it incorrectly

Agreed, I wouldn't do the wheel well covers for this reason

But I think the underbody trays and maybe a bigger kammback spoiler would be a safe bet

There are a few aftermarket spoilers for the Sonic but most of them are just for ricer looks rather than fixing the low pressure zone behind the rear window

 

[MyLonewolf25]

Agreed, I wouldn't do the wheel well covers for this reason

But I think the underbody trays and maybe a bigger kammback spoiler would be a safe bet

There are a few aftermarket spoilers for the Sonic but most of them are just for ricer looks rather than fixing the low pressure zone behind the rear window

I'd just build off the old one and make it curve downward
Extend it off the sides and inward from the side of the body

Again
Doing any of this can seriously hurt mpg if done incorrectly
And there may be easily changed places that you wouldn't think about unless you can put it in even simple simulations

Stuff that would seem beneficial can be detrimental

Fluid
She's a fickle mistress
A couple relevant videos here I DEFINITELY RECOMMEND
https://youtu.be/pXYJpXKMp_E
https://youtu.be/dQvCNEhuszw



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