Improving the Drag: Lowering and under car aero: - Chevy Bolt EV Forum
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post #1 of 15 (permalink) Old 03-18-2017, 05:46 PM Thread Starter
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Improving the Drag: Lowering and under car aero:

Hey Everyone,

Just picked up my Bolt on Monday and I already have the mod bug. I have been modifying cars all my life and road racing them (willow springs, cal speedway, etc.). This car is a lease so I am thinking cost effective improvements that can improve aero thereby improving range and handling.

I am thinking of buying a set of lowering springs as soon as they become available, and then fabricating some aluminum panels to continue the flat bottom of the battery pack all the way to the rear bumper.

Shouldn't be too expensive, springs are usually 200-300 and aluminum paneling will be around the same or less, plus my time to fabricate mounting points that are removable without any permanent modifications to the car itself by using existing bolt locations, etc. on the car.

Looking for any input or suggestions, maybe some engineers on the boards would like to chip in.

I understand some owners will feel this is stupid, or a bad idea - I thank you in advance for your opinion but would like to keep this thread on topic with people who might be interested in the same thing in case someone searches this topic in the future, please PM me if you still want to share those opinions.

Thanks!

-George
2017 Bolt EV Premier (Black)
AeroViroment L2 Home charger
3M Crystalline Tint windshield and front doors, 3M 20% tint rear doors and hatch
Kenwood 300W RMS amp with MTX Slim 10" Subwoofer
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post #2 of 15 (permalink) Old 03-18-2017, 06:26 PM
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I'm with you on the lowering springs - the OEM suspension sits the rear way too far up in the air, IMHO.
I'm not planning for five passengers with luggage.
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post #3 of 15 (permalink) Old 03-19-2017, 05:34 AM
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I like the ideas and always have the same mod bugs. Both my other 2 cars (Audis) are lowered with aluminum under plates. I discussed springs with a custom spring maker last Fall and they were interested, just needed the stock spring numbers.

Would much prefer the car lowered a bit, for aero as well as handling.

Caveats: Sharp crested driveway at work, no problem with stock suspension....until there is snow on it. (An issue for me, not for some I realize). I like the firmness of the stock suspension, fairly euro feeling. Not sure that feel would improve with shorter, stiffer springs vs. everyday ride quality in a people hauler/commuter. Would love to reduce the wheel gap if I could protect the battery better....hmm...maybe a better shield would help, as long as it allowed for proper cooling of the battery pack.
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post #4 of 15 (permalink) Old 03-19-2017, 12:35 PM
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Garage
Take pics of your work and post them!
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post #5 of 15 (permalink) Old 03-19-2017, 03:28 PM Thread Starter
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Originally Posted by Boltar View Post
I like the ideas and always have the same mod bugs. Both my other 2 cars (Audis) are lowered with aluminum under plates. I discussed springs with a custom spring maker last Fall and they were interested, just needed the stock spring numbers.

Would much prefer the car lowered a bit, for aero as well as handling.

Caveats: Sharp crested driveway at work, no problem with stock suspension....until there is snow on it. (An issue for me, not for some I realize). I like the firmness of the stock suspension, fairly euro feeling. Not sure that feel would improve with shorter, stiffer springs vs. everyday ride quality in a people hauler/commuter. Would love to reduce the wheel gap if I could protect the battery better....hmm...maybe a better shield would help, as long as it allowed for proper cooling of the battery pack.
I emailed Eibach to see if they want to use my car as a test car to develop a set of springs, they aren't too far from me hopefully they do it.

I haven't put the car on a lift yet but I am thinking Aluminum plates front and rear to close any gaps for turbulence and some diffusers on the rear plate, Ill paint it all flat back so it doesn't draw attention.

I am hoping the battery is pretty flat and I don't need to run aluminum plating along the entire bottom of the car, although it would protect the battery a bit against the elements but nothing major of course.

-George
2017 Bolt EV Premier (Black)
AeroViroment L2 Home charger
3M Crystalline Tint windshield and front doors, 3M 20% tint rear doors and hatch
Kenwood 300W RMS amp with MTX Slim 10" Subwoofer
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post #6 of 15 (permalink) Old 03-19-2017, 03:30 PM Thread Starter
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Originally Posted by wainair View Post
Take pics of your work and post them!
Will do but might be a while, Ill post pics and prices when I get to it incase anyone wants to try the same.

Now if only I had access to a wind tunnel will have to use cruise control and Kw meter for tests, same road, same temp, same wind. Hopefully I can replicate those conditions, going to be hard to measure a gain. The drag coefficient on this car is pretty bad so should be plenty of room for improvement, mainly from the rear I will probably start their first, test, then the front.

-George
2017 Bolt EV Premier (Black)
AeroViroment L2 Home charger
3M Crystalline Tint windshield and front doors, 3M 20% tint rear doors and hatch
Kenwood 300W RMS amp with MTX Slim 10" Subwoofer
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post #7 of 15 (permalink) Old 03-19-2017, 09:04 PM
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Originally Posted by XBS View Post

Now if only I had access to a wind tunnel
That's the thing. GM does have a wind tunnel and I'm pretty sure that if closing off the underside of the car made a significant difference on economy and therefore range, they would have done it. They would have used plastic instead of aluminum, but they would have done it. Likely there is just a tiny, if any benefit.

Lowering the car will certainly help handling and maybe aerodynamics. It might be awhile before you get a spring manufacturer interested though. They like to see numbers of cars sold, so potential customers before they commit. Maybe there are a similar springs from another car that they can do right away?
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Last edited by DaV8or; 03-19-2017 at 09:28 PM.
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post #8 of 15 (permalink) Old 03-20-2017, 12:13 AM
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You can do a quick reasonably priced lowering of the Bolt with a set of 16" wheels and tires, and with low profile tires you can easily get about 1" of lowering, with plenty of stock suspension travel.
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post #9 of 15 (permalink) Old 03-20-2017, 08:21 AM
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You could just do that... but I doubt you'll get any nicer handling and cool affect off of it haha. I don't know if it'll be as effective either.
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post #10 of 15 (permalink) Old 03-24-2017, 06:35 AM
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The 225/40/18s I'm looking at should lower by about .4" vs. the stock tire size. Yes, I know, not super aggressive, but this is a family hauling ev. Ok for the Summer, but realizing I'll need the lil' extra clearance in winter for the snow on our driveway crest. Lowering cars by tire size isn't my usual modus operandi, but works in this case. I've already looked at lowering springs but that wouldn't help me for winter, tire profile will.
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