Previously there used to be two 12" subwoofer boxes being free-aired out the back of the car. I just used them until I could find something better. Surprisingly, 2 years later they are beating strong except for the rips in the surround due to over extension. The back sides were dusty but not too damaged at all. Anyways, now while the car is down and I am waiting for electrical components to ship, I might as well take a few days and fix it right. My question is though, should I fiberglass it or weld it? I would want to have it somewhat domed out in the back to give some extra room for the speakers magnet if possible. Here is an idea a saw a while back and liked the finished result. Not sure who posted these but I loved your work.




After ripping out the boxes, this is what I am left with. Currently being sealed up with duct tape and cardboard.

From the top looking down


and the bottom looking up.




Now, what would you recommend? Weld it up and shape the metal to fit a speaker or fiberglass?

PM sent...

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3.4L Supercharged 87 GT and Super Duty 4 Indy #163

So, would the be my best option to maximize airspace while keeping legroom?

Sorry i'm not an elite photoshopper. but heregoes.

Red lines would be new welds and metal going in.
Green lines would be cuts and the green dotted area would be the metal removed.

Keep in mind this green lines will extend clear up to the rear window if there are no obstructions. If my idea is wrong please let me know as this is only the planning stage.

I'm no engineer but it looks to me like if you remove that much metal out of the firewall, you have seriously compromised the integrity of the spaceframe. If you're in a head-on collision, the car is gonna fold up on top of you.

I would weld those holes back up and make a custom sub box in place of the console box. You could relocate the ECM behind one of the seats. You really only need one sub but you could stack two smaller ones in that space.

Jonathan

quote Originally posted by Shill: Keep in mind this green lines will extend clear up to the rear window if there are no obstructions.

CAN'T DO THAT. You'll have the entire back of the passenger compartment open to "free air" and worse off than you started.

That channel is only about 8" high. It's welded to the firewall for rigidity. You want to sheet metal cutout to stay within that channel and not cut the welds or that channel. It's already partially open, so you can feel how high up you can open up the sheet metal, but staying within the channel area.

See here: https://www.fiero.nl/forum/A...060811-1-041889.html

[This message has been edited by fierosound (edited 04-10-2010).]

What about removing the top and bottom lip of that channel and extending them to the bottom of the car and also upwards to the bottom of the window. Basically would be more of an extension on the firewall I currently have.

[This message has been edited by Shill (edited 04-10-2010).]

quote Originally posted by Shill: Here is an idea a saw a while back and liked the finished result. Not sure who posted these but I loved your work.

Thank you, I'm glad you like it.

I'd listen to what Fierosound is telling you. It was his install that I used as a basis for mine. He is VERY knowledgeable on this.

quote Originally posted by Shill: What about removing the top and bottom lip of that channel and extending them to the bottom of the car and also upwards to the bottom of the window. Basically would be more of an extension on the firewall I currently have.

What you suggest at the bottom is doable - the idea for the upper end, not so likely (there's an engine there).

I think your best bet at this point is to look at a chassis with stripped interior and empty engine bay so you can see what's on the engine side of the firewall. You'll then get a better idea of what you can and can't do with the fuel and vent lines, decklid hinges, decklid torsion bars and everything else on that side.

You can then decide to do what you like.

Now, with that being said, would it be better to have a squared box or will angles affect it much? Such as if I wanted to make the channel deeper to remove the need for a bigger box inside the cabin and to allow for a bigger/deeper speaker. As for calculating airspace, will that be calculated with or without the mass of the driver?

Also, do they vary from year to year? Let's say I were to do all my designing from looking at an 88 that is currently stripped and then apply it to my '84 without having to remove everything. Seats and interior moldings are nut such a big issue to me. It's the engine bay that I don't want to mess with much.

[This message has been edited by Shill (edited 04-11-2010).]

quote Originally posted by Shill: It's the engine bay that I don't want to mess with much.

DIY subwoofers http://www.diysubwoofers.org/

Chassis are all the same. Are you aware the fuel filler pipe runs through the channel on the driver's side?

I'd say fix the bottom area. Leave the channel and everything up from that as is. Look at getting quality subs with neodymium magnets
- they are more efficient, powerful and smaller - and box depth won't be a problem.

If after looking at that 88 chassis you have, you decide you still want to build a new entire back firewall, whatever you want to do is strictly up to you.

See what others have done:
https://www.fiero.nl/forum/A...070315-1-059592.html
http://www.fierosearch.com/...0sub&Action=DoSearch

[This message has been edited by fierosound (edited 04-12-2010).]

quote Originally posted by fierosound: Are you aware the fuel filler pipe runs through the channel on the driver's side?

Yes, I am aware. It wouldn't be too hard to re-route the fuel line I wouldn't think especially with newer stainless steel braid. I am only wishing to do more work now to leave my self more room so that I may have more options when selecting a speaker such as 8" 10" 12", single coil, dual coil, etc...

One last thing. From the P22 Parts Book - some pieces of how the firewall is put together - good luck.
More: https://www.fiero.nl/forum/A...070315-2-073338.html

[This message has been edited by fierosound (edited 04-12-2010).]

i'd be welding it; that and thoes holes are currently a fire and exhaust hazard.

How a couple other guys have done it to mount speakers higher up in firewall.

From here: https://www.fiero.nl/forum/A...020511-2-016830.html


...and here: https://www.fiero.nl/forum/A...090219-1-066435.html

I was unaware that this was the pipe you were describing. I was picturing the very small, pencil size line that runs quite a bit lower. This is not something that can be easily relocated.

quote Originally posted by Shill: I was unaware that this was the pipe you were describing. I was picturing the very small, pencil size line that runs quite a bit lower. This is not something that can be easily relocated.

Here's the engine bay side where it enters the channel. You should be able to see this on your 88 chassis.

[This message has been edited by fierosound (edited 04-12-2010).]

Updates.





Getting ready to glass later today.

Made a new thread with a simple question, hopefully Cliff can merge the two into one.

Having troubles squaring off the foam on the other side, will post more when done.

Never done this sort of fiberglass before, i've only done repair work so feel free to point out what you please. Have a few small holes to fill yet where the fiberglass is a bit thin, but here are close to the final pics.