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Discussion Starter #1
I spent a good part of today working on a false floor/amp rack for my M3. I didn't get much done physically, but I think I have most of the layout thought out. Since, I've never really done anything like this before I wanted to see if any one notices any problems with my design or can offer any improvements. I'm also planning to add an Audison Bit1 and a Car PC later on, but I'm not really sure if there is room for them here. If anyone sees how I might be able to fit them in, please let me know. Thanks!

These are the basic supports for the amp floor. These will be velcroed to the car so I can remove the amp setup for any reason. I'm planning to make the lower support bigger (~5in). I don't think I can do much with the upper support as the floor is uneven on the left, and is slanted on the right. My car doesn't have a spare tire, so the cut out is for a styrofoam piece that holds a fancy air compressor.



This is the floor to hold the amplifiers. This will be secured to the supports.



This is where I plan to place the amplifiers. They will be on small stands so that the wires can run underneath them and through the amp rack floor.



I plan to build supports on each side like this to support the false floor. I'm going to try and add one to the rear too, but the curved trunk floor might make it tough. I plan to carpet the amp floor and the side supports. I also might extend the sides out by a 1/2in to give the lower amp some more room. Any ideas for fans? I was thinking two at the top and two at the bottom, but again the curved trunk floor might pose some problems. Could I place the fans on the left and the right? The trunk has a vent on the far right as that's where the battery is.



I also saw this example of a false floor. I didn't know if there was any advantage to having the amp floor extend to the available space. I would still have to add supports on the left and right.

 

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Keep in mind your power runs and signal paths to avoid noise in the system before finalizing amp/processor placement
 

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No spares in those M3's huh?

Learn something new every day.
 

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Discussion Starter #4
Keep in mind your power runs and signal paths to avoid noise in the system before finalizing amp/processor placement
Will do, Thanks.

No spares in those M3's huh?

Learn something new every day.
Nope, The exhaust is where the spare would be. The normal 3-series only has the exhaust on the left, while the M3 has it centered at the rear of the car.
 

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The older M3's had spares but most people removed them for the 37lbs of weight savings.


If you wanted to make the curved edge you could either cut out several pieces That match the curve and are 1/2 or 3/4 of an inch wide and glue them together to match the height of your rack or you could try the "kerfing" technique. For more explanation on that goolge kerfing. I've always wanted to try the kerfing thing myself. :)

P
 

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The older M3's had spares but most people removed them for the 37lbs of weight savings.
or they could simply leave 4.2725 gallons of gas out at the next fill-up. That's 37 Lbs, which indeed is one heavy-ass spare, they fill it with water?
 

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I think you are going to have to raise the factory floor a touch with those amplifiers (iirc DLS amps are over 2" tall). With that being the case, there's a hell of a lot sturdier ways to build up a false floor in a 3 series, and you can make them light and removable with only a few screws.

Something like this:


That floor is about 2" taller than stock - which is nice because it allows you to remove the factory plastic panels on both sides of the trunk, so now you have a nice flat floor. It also allows a ton more space for wiring.

Just my $0.02
 

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Discussion Starter #8
rcurley55,

I actually tried to model my design off of yours. I've seen your various threads on here and on e46fanatics.com. I'm aware that I'll have to raise the floor and I've tried to factor that in.

With that being the case, there's a hell of a lot sturdier ways to build up a false floor in a 3 series, and you can make them light and removable with only a few screws.
What would you do differently to achieve this (light, sturdy and removable)? I've tried to see how you have built yours, but the pictures I've seen (there are a few on your photobucket) aren't that revealing. Since you have much experience with the M3, any advice that you can give me would be great!
 

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Chad the old M-Contour rims and then the Pole-position tire on there was a heavy sucker. Replaced my M-rims with Fikse FM-5 which combined withe the Yokohama tires I saved quite a bit of weight. I left out the spare so I could fill it up with audio equipment.

So what are the measurements of the amps etc?

P
 

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I am actually doing the same in my car - I'll get pictures of it when I get home tonight. I used 1/4" MDF in the bottom and glassed around it where the sides and curve are - sits right down in that whole section and kind of "snaps" in place. My amps are almost the same height so I will only have to raise the floor about 1/2", maybe 3/4" from where the factory floor is.
 

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rcurley55,

I actually tried to model my design off of yours. I've seen your various threads on here and on e46fanatics.com. I'm aware that I'll have to raise the floor and I've tried to factor that in.



What would you do differently to achieve this (light, sturdy and removable)? I've tried to see how you have built yours, but the pictures I've seen (there are a few on your photobucket) aren't that revealing. Since you have much experience with the M3, any advice that you can give me would be great!
We're making progress - baby steps though - pic - E46Fanatics

That has some pics of the build - essentially, use the frame rails as the base and attach a "box" for lack of a better term to hold the amps. Just mock something up with 1/2" mdf for the sides, 1/4" mdf for the bottom (it's plenty sturdy and you can add a brace to the bottom side if you like.

That gives you the most clearance. The main issue is that the ribbed section closest to the bumper reduces overall depth of the spare tire well - assuming you want your amp rack to be flat and level.

The frame rails are your best reference for "square" in there, so build everything off of them. The only things to be aware of are the two shocks (one in each frame rail) that are connected to the bumper. If you look carefully through the holes in the framerail, you can see them.

Here are more of my musings over the years about my installs in that car:
E46Fanatics
 

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What did you use for that trim ring where the cover sits in above the amps? That is real clean looking. I haven't built the top section for the floor yet as I haven't figured out exactly how to make it look nice but that turned out excellent.
It's 1/2" MDF with a 1/4" round-over. Sanded, filled where necessary, and rattle-can painted.

Pretty simple, I just made a recess in the amp rack so the trim ring sat flush with the top of the amp rack. Then the false floor (1/4" mdf) laid right on top - if you cut the false floor correctly (this was done in 5 pieces - the center section, two "wings" near the front of the trunk, and two additional wings near the rear) and carpet it as one piece, you need no additional fasteners. It just lays on top of the amp rack. I added a few braces near the front of the trunk, where there was no amp rack to support the floor so it was nice and solid.

you can see the recess here if you look carefully:


I never understand why people continue to use such heavy stock for false floors (I have looked at build logs where people are using 3/4" material for a floor).

Thanks for the compliment. The E46 trunk is a piece of cake to work in - the rest of the car is another story...
 

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with false floors I usually recommend using Birch plywood, too. It is REALLY light compared with MDF and very stiff. It doesn't cut as well (MDF is the ultimate to cut and shape, as we all know), but it makes a fine starting layer and weighs a lot less.
 

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Discussion Starter #16
I am actually doing the same in my car - I'll get pictures of it when I get home tonight. I used 1/4" MDF in the bottom and glassed around it where the sides and curve are - sits right down in that whole section and kind of "snaps" in place. My amps are almost the same height so I will only have to raise the floor about 1/2", maybe 3/4" from where the factory floor is.
That would be great if you could post up some pictures. Thanks!

We're making progress - baby steps though - pic - E46Fanatics

That has some pics of the build - essentially, use the frame rails as the base and attach a "box" for lack of a better term to hold the amps. Just mock something up with 1/2" mdf for the sides, 1/4" mdf for the bottom (it's plenty sturdy and you can add a brace to the bottom side if you like.

That gives you the most clearance. The main issue is that the ribbed section closest to the bumper reduces overall depth of the spare tire well - assuming you want your amp rack to be flat and level.

The frame rails are your best reference for "square" in there, so build everything off of them. The only things to be aware of are the two shocks (one in each frame rail) that are connected to the bumper. If you look carefully through the holes in the framerail, you can see them.

Here are more of my musings over the years about my installs in that car:
E46Fanatics
Yeah, i've seen those pictures. You don't happen to have any more do you? I'm interested in the slanted piece at the rear of the box. It also looks like you built a square and then secured a piece inside of the square to hold the amps, correct?

Do you think I could secure mine to the frame rails with velcro instead of screws like you did?

Your link doesn't work. I've seen many of your posts on E46Fanatics before, so i'm assuming that's what it was a link to.

Pretty simple, I just made a recess in the amp rack so the trim ring sat flush with the top of the amp rack. Then the false floor (1/4" mdf) laid right on top - if you cut the false floor correctly (this was done in 5 pieces - the center section, two "wings" near the front of the trunk, and two additional wings near the rear) and carpet it as one piece, you need no additional fasteners. It just lays on top of the amp rack. I added a few braces near the front of the trunk, where there was no amp rack to support the floor so it was nice and solid.
Do you have any pictures of your false floor? I understand what you did, i'd just like to see some close ups of the underside of the winged sections.

with false floors I usually recommend using Birch plywood, too. It is REALLY light compared with MDF and very stiff. It doesn't cut as well (MDF is the ultimate to cut and shape, as we all know), but it makes a fine starting layer and weighs a lot less.
Thanks, i'll keep that in mind. BTW, i'm using 1/4in and 1/2in MDF incase anyone was wondering.
 

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Discussion Starter #17
So what are the measurements of the amps etc?
(W X D X H)
The A4 is: 18.30 x 9.45 x 2.87 inches
The A6 is: 16.15 x 9.45 x 2.87 inches
 

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I never understand why people continue to use such heavy stock for false floors (I have looked at build logs where people are using 3/4" material for a floor).
Truth. Beyond the weight, it just takes up more space. You typically have to put spacers under the top layer anyway. Those spacers do a good enough job of keeping the top layer sturdy. I’ve never used anything but ¼” (anything) and haven’t had any issues.

Thanks for posting your pics.
 

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This is what I have

DSC_0001.jpg

I'm not completely done yet but its close. I used a piece of 1/4" mdf cut out to lay down in the bottom between the frame rails. I put fiberglass mat down all around the edges of it on the sides and where the curve is, dropped the mdf in place and then added resin. Once it set up I popped it out and added another layer of glass and resin. It fits nice and snug and the mdf is directly on the floor of the trunk.

These amps are about 2 5/8" tall so close to what you have. When I do the false floor I will have to add between 1/2 to 3/4" along the rails and that will be it - that will allow me to run the wires out underneath the floor and maintain minimum height possible. I don't have the side panels in yet - have to run the speaker wire before I can do that and finish routing the wiring, then it will be build the false floor itself. I was going to use birch but home depot only had it in the pre-warped variety so I bought 1/4" mdf instead and added a couple of supports towards the middle just in case - I use my trunk so I don't want it collapsing.

In the bottom layer of mdf I used 10-32 nutserts and then used cap screws threaded down into them to hold the amps, eqs, and xover down. The eqs and xover are actually on a raised pedestal so I can run some of the wiring underneath and bring them up somewhat level with the top of the amps.

I used the well underneath to run all my power wires - it comes in on the right side from the main fuse right off the battery, drops in and runs over to a distribution block mounted underneath where the xover is. If you pull the xover you can access the fuses in the distribution block and all the set screws for the power cables. From there the power goes to each amp - I turned the amps so all of the power cables were on that end so I didn't have to worry about lifting the bottom to run the wiring underneath. The RCA interconnects go underneath the amps for each channel and also underneath the pedestals.

Anyway - that is about where it is at for the moment.
 
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