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BRZ Second-Gen (2022+) -- General Topics General topics for the second-gen BRZ


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Old 12-23-2020, 10:22 AM   #15
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I love me a Targa, and wish a proper one was available in the Twin. The correct way to do it is what Chevy does with the Corvette, build it into every car from the beginning.

The only one I've actually owned was an '83 Camaro Z28 Conversion. It had a black convertible top that stretched over to cover and worked amazingly well. The car probably did have some noticeable flex in it as there was no real stiffening to my knowledge (I bought it off the dealer floor, conversion already done). I can tell you it was definitely better than the convertible conversions they were doing at the same time that felt like pretzels when you drove them.

For @Red-86 I've owned lots of cars with sunroofs and every one of them leaked at some point. Not a fan.

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Old 12-23-2020, 10:32 AM   #16
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At a minimum, how about a large removable sunroof, such as used to be available on the Porsche 924? I think that by leaving the perimeter roof channels intact, most of the structural integrity of the body is maintained. I don't think the sheetmetal in the middle contributes much.
A continuous (i.e. no sun/moonroof-hole) thin, lightweight shear panel contributes a LOT to torsional stiffness, while weighing practically nothing. Putting a big hole in the roof requires a somewhat massive frame around the hole => heavier with less torsional stiffness. Also more $$$.
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Old 12-23-2020, 11:12 AM   #17
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Do you mean T-tops? T-tops (keeping a center bar) were all the rage in the 70ís and 80ís..
The 86 unibody already has what looks like ďt-topĒ cutouts?
Iím not a structural engineer (!) but that doesnít stop me (: from speculating on the ease of which two small *manually* removable panels couldnít have been ďcutĒ from the roof section & fitted w/o reducing rigidity or adding much up top weight.

*But as some of us already mentioned I doubt anyone but die hard fans of 70-90s throwbacks (why I drive this car) would appreciate that design.
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Old 12-23-2020, 11:13 AM   #18
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As Dadhawk said, when it's part of the design from the beginning it can work without the added weight or twisting. Think Lotus Elise.
(By the way, we have had three Subarus with sunroofs and none have leaked. Just saying YMMV)
I'll just put this here for you all to enjoy, reminisce and think about what you are/have missed.
https://www.automobilemag.com/news/1...s-to-remember/
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Old 12-23-2020, 11:28 AM   #19
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The 86 unibody already has what looks like “t-top” cutouts?
I’m not a structural engineer (!) but that doesn’t stop me (: from speculating on the ease of which two small *manually* removable panels couldn’t have been “cut” from the roof section & fitted w/o reducing rigidity or adding much up top weight.
Aerospace structural engineer here
The thin, lightweight shear panel that is the outer roof contributes significantly to roof shear stiffness and chassis torsional stiffness. Removing this shear panel leave you with an open picture-frame that is relatively free to deform as a parallelogram (even with the central "T" brace). Shear panel weighs very little but gives a LOT in terms of shear and torsional stiffness.
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Old 12-23-2020, 11:33 AM   #20
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Aerospace structural engineer here
The thin, lightweight shear panel that is the outer roof contributes significantly to roof shear stiffness and chassis torsional stiffness. Removing this shear panel leave you with an open picture-frame that is relatively free to deform as a parallelogram (even with the central "T" brace). Shear panel weighs very little but gives a LOT in terms of shear and torsional stiffness.
By that same token though, if you have some type of lightweight (say CF) roof panels in place, wouldn't they provide that same rigidity, even if they didn't when removed?
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Old 12-23-2020, 11:36 AM   #21
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The 86 unibody already has what looks like ďt-topĒ cutouts?
Actually, it doesn't. The frame in the roof above the door would have to come off as well for a true T-Top. That's a pretty significant piece.

Technically you could split the middle frame member, move it out towards the ends and do a sunroof without much loss, but you would lose the "bubble" part of the roof on each passenger side to do so (or rather the low part in the middle.
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Old 12-23-2020, 11:38 AM   #22
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Yes, I would love a targa or TTops, or even a nice sunroof. No, I would absolutely not hack up a current model. This is something that would need to be designed in from the factory.

I loved the TTops in my old 300ZX. They never leaked, but they would make a little noise as the car got older. Totally worth it.

My MR2 had a large removable sunroof you could store under the hood, since the engine was in the back.
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Old 12-23-2020, 12:09 PM   #23
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The 86 unibody already has what looks like “t-top” cutouts?
I’m not a structural engineer (!) but that doesn’t stop me (: from speculating on the ease of which two small *manually* removable panels couldn’t have been “cut” from the roof section & fitted w/o reducing rigidity or adding much up top weight.

*But as some of us already mentioned I doubt anyone but die hard fans of 70-90s throwbacks (why I drive this car) would appreciate that design.
How do you remove the top section of the door frame without reducing rigidity?
Also, this platform is flimsy enough, to the point where my trunk lid has enough later movement under load to butt up against the inner portion of the rear quarter panel/trunk opening just above the tail lights and to the point of removing paint on both sides.
As for the MR-2, it's the '93 without T-Tops that is the most sought after, and command the highest resale.
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Old 12-23-2020, 12:10 PM   #24
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By that same token though, if you have some type of lightweight (say CF) roof panels in place, wouldn't they provide that same rigidity, even if they didn't when removed?
The manufacturer is going to have defined *minimum requirements* for strength and for stiffness, which will have to be met in all configurations. So chassis/frame structural design will be driven by the "no-roof" configuration. So even with structural roof-panel(s), you'll still have the additional structural mass built in and just enjoy added stiffness with it installed. An the customer is gonna want an *easily* removable panel or panels, not one that they have to bolt in to make it a rigid part of the chassis structure.

IMO best to let convertibles be convertibles, and let fixed-roof coupes be fixed-roof coupes and enjoy the weight benefits. Corvette has suffered a massive weight penalty since 1968 introduced T-tops. C5 and C6 Z06 enjoyed a bit of a weight reduction with fixed roofs. Then for C7 they decided "who cares about weight, we'll supercharge it!" Now for the C8 they've decided they *really* don't care about weight
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Old 12-23-2020, 12:11 PM   #25
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Actually, it doesn't. The frame in the roof above the door would have to come off as well for a true T-Top. That's a pretty significant piece.

Technically you could split the middle frame member, move it out towards the ends and do a sunroof without much loss, but you would lose the "bubble" part of the roof on each passenger side to do so (or rather the low part in the middle.

I donít want to give up the double bubble roof for a sunroof or targa top. Not to mention you introduce more flex into the car. No thanks! There is a reason the coupe version of the MkIV Supra is the most sought after.
Donít get me wrong I think sunroofs and targa tops are fun, but the cars Iíve owned with them I found I never used them much.


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Old 12-23-2020, 12:25 PM   #26
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As for the MR-2, it's the '93 without T-Tops that is the most sought after, and command the highest resale.
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There is a reason the coupe version of the MkIV Supra is the most sought after.
Donít get me wrong I think sunroofs and targa tops are fun, but the cars Iíve owned with them I found I never used them much.
Ditto FD RX-7. Non-sunroof models are the most sought-after.

90s Z-car fans would kill for a slick-top Z32 turbo, Nissan didn't offer one
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Old 12-23-2020, 02:11 PM   #27
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I donít want to give up the double bubble roof for a sunroof or targa top. Not to mention you introduce more flex into the car. No thanks! There is a reason the coupe version of the MkIV Supra is the most sought after.
Technically you wouldn't have to give up the double bubble for a targa. A hard top could remain pretty much as it is.
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Old 12-23-2020, 02:37 PM   #28
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Ditto FD RX-7. Non-sunroof models are the most sought-after.

90s Z-car fans would kill for a slick-top Z32 turbo, Nissan didn't offer one
The slicktop Z32 was lighter. People wanted them for track cars. I get that.
The reason they were rare and the reason Nissan didn't make a slicktop TT is because they didn't sell well when they were new - because the TTops were awesome The slicktop was the budget Z.
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