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Old 12-02-2017, 10:05 AM   #1 (permalink)
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Chevy Volt Belly Pan

So I recently traded in my venerable VW TDI for a Volt. Although the ol' VW was getting 50-60mpg with plenty of mods the nickel and dime repairs were starting to take their toll. I love to tinker but spending every other weekend replacing a $15-30 dollar part was getting annoying.

Anyways on to the point of this post. I ended up buying a 2015 Volt. Upon looking under the car I was confused by the lack of an engine belly pan. I thought it might be missing but a phone call to the dealer and subsequent internet searches reviled that's just how GM did it.(or didn't) So while aero was a concern my primary reason for the engine pan was all of the random things I've accidentally hit over the years on the road and the need for some protection.

Initially while I did my research I jumped under the car and threw some coroplast with a Thermo Tec heat shield since the exhaust was practically touching the coroplast. I just used the factory small screws that also hold the factory aero in place. Nothing fancy. It measured 30in x 24in. I had a 36x24 piece of coroplast in my garage.

Once I realized that there wasn't anything missing from my car I fashioned up a more heavy duty shield. I used some aluminum diamond plate I got on sale at the local big box store. It initially measured 36in x 36in. The two frame rails that run down the car are roughly 30 inches apart. (outside to outside) GM was nice enough to leave two 3/8-16 threaded holes midway down each frame rail and I just happened to have a bunch of matching bolts! The threaded holes don't go all the way through so you'll have to check your depth, I used bolts that were 2 inches long but I also put some old scrap anti-vibration mat in between the plate and the frame as a makeshift bushing.

Up front there is a cross member between the frame rails. It isn't level with the 3/8-16 holes further back. (about 2 inches higher, reference point is the ground) It had two nice holes that also don't pass all the way through the rail but there didn't appear to be any obstructions above them if you wanted to drill them out up top. I used a rivnut tool to set M8 threads in the holes. The M8 was a touch small, I'd recommend an M10 but the next size up I had was 3/8 which was way to big. The M8s may end up working their way out of the holes in time in which case I'll set a larger rivnut or I'll just drill out the top of the hole and put a nylock nut and bolt through.

There are various holes in the two main frame rails that do pass all the way through and I considered using them before I found the 3/8-16 threaded holes. If you end up going 36 inches back from the front cross member you'll need to cut the corners off your plate as there are some mounting points for the suspension that reside back there. Also there is a bolt that hangs down in the middle that you'll need to drill a hole for back there.

In the pictures you'll see my coroplast panel. The six mounting points. The front two I used much smaller bolts but for the picture I put two really long ones in to make their location obvious. The last picture is the completed plate.

If there are any questions, I'd be glad to answer them!






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Old 12-02-2017, 12:44 PM   #2 (permalink)
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Looks very nice. Did it add any engine noise or vibration? My coroplast belly pans make some noise.
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Old 12-02-2017, 03:19 PM   #3 (permalink)
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Not as of yet.....

I won't get it up to sustained highway speeds until mid-week, it'll be city driving until then. I was worried about the noise so I added a layer of Thermo Tec insulation to the topside of the aluminum, all of my bolts have rubber washers and I put some rubber between the frame and the plate at the four primary mounting points.
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Old 12-04-2017, 08:40 AM   #4 (permalink)
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Nice job on the pan. It would be really cool to see some A B A testing if you had the time.
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Old 12-04-2017, 04:51 PM   #5 (permalink)
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Nice! It should help your engine get up to temp when in ICE and hold heat in the engine bay when it is off. I can't believe Chevy left that open so road debris can get in. I have a Panzer Plate on my mk IV TDI.
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Old 12-05-2017, 03:36 PM   #6 (permalink)
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Looks sharp.

It blows me away every time I see where a major manufacturer has left some low hanging easy fruit that could improve their fuel economy numbers. Open wheel wells on the Prius, too-large grille openings, this gaping chasm in the Volt, etc.

I keep wondering if that's an opportunity they're holding in reserve, a chance to improve the next model with something that doesn't take a lot of ingenuity to make it work.
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Old 12-05-2017, 05:33 PM   #7 (permalink)
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So that's what the underside of my car looks like!

That belly pan looks really clean - I might have to put one on my Volt since they were nice enough to leave some bolt holes. Thanks for the pics, shows me right where to look
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Old 07-14-2019, 01:51 PM   #8 (permalink)
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That looks super clean. I've been experimenting with doing this under my Volt however I have been trying to find a large enough piece of coroplast or something to use under the car. I tried an initial prototype of my own with cardboard which ended up coming loose after some time (nothing was near the exhaust in case you were wondering). Have you noticed any improvement in mileage? Also, how much did this project cost? I had not thought about using aluminum diamond plate but I might consider it if is not too expensive.
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Old 07-15-2019, 11:58 AM   #9 (permalink)
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The most expensive part was the diamond plate itself, so that really depends on what you can find on the cheap. I used the diamond plate because I found it on sale. Plain sheet metal would work as well. For the rest of the parts I think it was $5-10, really depends on what grade of bolts you use.

As for mileage.... I dunno. Between the front air dam and side skirts, (IMO) the plate isn't really interacting with the air enough for me to pick up on any change. Other drivers might be able to see a difference but my main concern was protection. Oil filters and oil pans tend to not take road debris/stones very well. That low hanging, front facing filter just gave me the hibby-jibbies.

On another note, longevity has been great. If the date on my original post is correct I did that back in Dec. 2017. While I've been under the car plenty of times to either tinker or do maintenance, I've never been forced to get under the car to reattach anything. Though I would recommend using some thread-locker blue on the bolts once you have something you're happy with.

Good luck, and I'd love to see what you come up with!

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