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Smity42
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Can you remove the rear firewall?

Post by Smity42 »

Hi Guys,

Can you remove the rear firewall and rear side brace bits from a GTV?

The bits I am talking about are shown in the pic below.

The car will be caged with bracing between the shock towers, but I am not sure how structural this piece is. I'm sure I've seen pictures on here of cars with this removed though.

Cheers,

Martin

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Re: Can you remove the rear firewall?

Post by Maurizio »

Remove it, not structural at all
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Re: Can you remove the rear firewall?

Post by Smity42 »

Maurizio wrote:Remove it, not structural at all
Thanks mate!

I didn't think it was, but thought it best to check, can never be sure with the ol' Monocoque.

Cheers,

Martin
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Re: Can you remove the rear firewall?

Post by Mats »

Maurizio wrote:Remove it, not structural at all
What? Are you mad? :shock:

Thought you were into frames and shit? :D


I would not remove it unless you do a "cage" that is really a spaceframe.
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Re: Can you remove the rear firewall?

Post by Maurizio »

The car will be caged with bracing between the shock towers
When the cage is done properly eg end on top of the shock tower it will be even better!

Mats, what does this plate (rear fire wall) do, what a cage doesn't? :roll:
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Re: Can you remove the rear firewall?

Post by Mats »

well, take a box, remove one wall and replace it with a really stiff bar across the hole from the midpoint on one wall to the opposing. Then try to twist the box.

Do you think the original or the modified is the stifest in twist? I'd go for the original any day...
Even better, the original with the bar. :)
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Re: Can you remove the rear firewall?

Post by Maurizio »

:oops: a cage and a cage can be two different things..

So yes Mats true.
If it is a standard screw in type off cage, your right, leave it in and it will be stiffer then without.

If the plate was flat, vertically and located between the shock towers (with some nice big holes, leaving a nice cross), I would say yes... it is helping effective and at a minimal weight penalty.

Resume: it kind off depends a lot on the layout off the cage, what helps or is only redundant (read: useless weight). :lol:
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Re: Can you remove the rear firewall?

Post by Smity42 »

Interesting difference of opinions.

I might mock up my cage idea in paint and put it up for you guys to critique... one of the reasons I want to remove the firewall is to get access to tie the cage to the shock towers, not the wheel well.
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Re: Can you remove the rear firewall?

Post by Maurizio »

ooooh no we agree, the box story is true.
But leave a wall out and replace it with two diagonal strings to each corner and it is stiff again.

What I want to point out is that the original plate isn't very effective.
Also there are more forces in the back area playing a role then just the shocks.... springs & mounts of the watt-linkage.
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Re: Can you remove the rear firewall?

Post by kevin »

Have you checked your FIA rules before you remove it or do you have another plan to compartmentalise your fuel tank. I did not and have to put a back board in . Bull sh*t as if you roll and split tank the petrol will just come through. We dont have a clause in our rules stating an FIA fuel cell is sufficient. Then again is your tank under the car .
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Re: Can you remove the rear firewall?

Post by MD »

Marty,

Next time you are at the track with Jacko, ask to see inside the boot to show you how to make this modification to keep and improve rigidity and isolate the fuel tank which is under the car which I presume this GTV 2.o also has one but on the opposite side to the sedan.
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Re: Can you remove the rear firewall?

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kevin wrote:Have you checked your FIA rules before you remove it or do you have another plan to compartmentalise your fuel tank. I did not and have to put a back board in . Bull sh*t as if you roll and split tank the petrol will just come through. We dont have a clause in our rules stating an FIA fuel cell is sufficient. Then again is your tank under the car .
That firewall doesn't really isolate the boot of the car anyway. There's holes in it, and a HUGE gap to the roof. The tank is under the car, but surge tank and feed pump will probably be in the boot, but isolated from the cabin in their own box.

MD wrote:Marty,

Next time you are at the track with Jacko, ask to see inside the boot to show you how to make this modification to keep and improve rigidity and isolate the fuel tank which is under the car which I presume this GTV 2.o also has one but on the opposite side to the sedan.
Hi MD,

Who is Jacko, and how do I find him?

The fuel tank is indeed under the car, on the passenger side.

Cheers,

Martin

Maurizio wrote:ooooh no we agree, the box story is true.
But leave a wall out and replace it with two diagonal strings to each corner and it is stiff again.

What I want to point out is that the original plate isn't very effective.
Also there are more forces in the back area playing a role then just the shocks.... springs & mounts of the watt-linkage.
Yeah, here is my design for a cage (mspaint spec, based loosely on a drawing I found on the CAMS website somewhere):

Image

The set up between the rear strut towers there I saw on another car on here, can't remember where now. The triangles brace the towers to the spring platforms, and I beleive there is a diff mount between the two strut towers that the bottom of the V can tie to.

Or would I be better off doing an "X" there instead of the "V"?

I haven't finalised the front suspension ties yet...

I'm pretty happy with the design, but you guys all seem to know your stuff so please let me know if I've gone wrong anywhere or if I can do anything better. Constructive criticism and flat out abuse are equally welcome :)
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Re: Can you remove the rear firewall?

Post by MD »

Marty,

I had a chuckle. The rear of that cage is off my old car, the Brick which is now owned by Jacko, ie Mark Jackson AROCAQ Club president. And yes the cage details are on this site. This set up provides for a connection of the spring bases which must be plated into the shock towers which are also plated. Both are welded together to form a spring /damper "module". This then is triangulated between the towers, to the floor at the transaxle rear support point. I have never seen anyone else build this set up but it is great and sets the rear of the car up very well.

As for the rest of the cage, well you sort of have too many bits and some are in the wrong places and superflous too. I am in Brizzy on the Southside and I am currently building an Alfetta GTV 2.0 race car like you. The cage is in. I suggest you send me a PM with you phone number and I will give you a call. You should come over and I will give you a hand with your design.

Cheers, MD
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Re: Can you remove the rear firewall?

Post by Smity42 »

Thanks MD, PM Sent.
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