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Discussion Starter #1
Does anyone have any insight on Lexan windshields? I want to do a full 4 windows and rear windshield Lexan conversion on my Quadrifoglio. Will the weight reduction be significant enough to make a difference. I was also gonna do a rear seat delete as well. I’m willing to pay and be the test dummy for this. Any info will be much appreciated. Cheers.
 

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There are 6 side windows, not 4. As far as I can tell, none of them are flat, although the tiny rear side-fixed ones seem to be very close to flat. Most appear to have a complicated compound curve.
Might these be available as GTAM spare parts? After all, they squeezed 100kg out of the car somehow.

I believe the weight of a typical rear window is around 15 pounds, probably 1/3 of that for the larger side windows. Typically Lexan is about 40% of that weight. I don't have numbers that are specific to Giulia. Thus, maybe 35 pounds lighter for the full set. Don't forget that the rear windshield has the radio antenna and a defroster built in. It is unclear to me if a glass compatible rear defroster grid is OK to mount on Lexan.

Scratch and UV resistant Lexan/polycarb is best for this application and for the front windshield strongly not recommended except for a dedicated track car. Windshield wipers will scratch the snot out of even the scratch resistant Lexan and impair forward visibility. Some Saudi chemical company claims to be able to make Lexan that meets standard requirements for all positions except the windshield. They do not seem to entertain contacts by anyone except major manufacturers though.
 

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Personally, I don't recommend doing the windshield in lexan or anything similar ever, and only do the other windows if it's a dedicated track car.

I say not the windshield because of strength reasons. I personally have yet to see any type of plastic that can withstand the types of high speed impacts that you might encounter, such as parts flying off the car in front of you, rocks getting kicked up, birds, etc. (I'm not kidding about that last one, ask me how I know...) Modern safety glass is unbelievably tough. Even on my super-light Porsche track rat, I have an OEM windshield, because the 15-20 lbs i might shed just aren't worth the risk.

I don't recommend doing the other windows for anything less than a dedicated track car multiple reasons. For one; most polycarb plastics you'll find to do this with will yellow with continued UV exposure. They also don't have the surface hardness, and will pick up a multitude of scratches over time from everything: tiny rock chips, bugs, the ring on your finger when opening or closing the door. Hell, even driving through heavy dust or sand can be abrasive enough. Both of those reasons will cause a surprisingly drastic decrease in visibility after as little as a few months. For two; it's really hard to get them to fit into place solidly and not rattle without riveting the edges all the way around, and I assume you want them to still work. For three, they do not insulate sounds from the outside. Driving a car with polycarb windows on the highway is loud: wind noise, tire noise, other cars on the road, you'll hear all of it. You won't hardly be able to hear the radio. It won't be worth it, I guarantee.

On the topic of overall weight reduction: you might see it if you have a data logger and do before and after runs, but you probably won't really feel it very much, except for the always possible placebo effect. As @lockem said, you'd probably get 30-40 lbs for replacing the windows, maybe another 30-40 for ditching the rear seat. If the seat weighs more than I think and the lexan weighs less than I think, than at most I'd say you're looking at 100 lbs total, from a 3800 lb car, which by my math is only a little over 2%. There's an old racer's rule of thumb that says losing 100 lbs = 10 hp = one tenth of a second off of the 1/4 mile time. In my experience, that seems about right. Another old rule of thumb is that you need to increase a car's horsepower by more than 10% before you'll really feel it seat-of-the-pants. Again, I've messed with this old adage, and it seems more or less accurate, meaning the Giulia needs a roughly 28hp bump to really feel it. So you're looking at the amount of performance increase of a decent intake or exhaust, and less than most available tunes, and most likely not enough to actually feel.

To summarize: Not much weight savings, less comfort, negligible performance gain, potentially less safety.

Edit: i only just now realized in the original post you did specifically say rear windshield, and I was talking about the front. Oops. Oh well, the rest of it still stands.
 

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Discussion Starter #4
Personally, I don't recommend doing the windshield in lexan or anything similar ever, and only do the other windows if it's a dedicated track car.

I say not the windshield because of strength reasons. I personally have yet to see any type of plastic that can withstand the types of high speed impacts that you might encounter, such as parts flying off the car in front of you, rocks getting kicked up, birds, etc. (I'm not kidding about that last one, ask me how I know...) Modern safety glass is unbelievably tough. Even on my super-light Porsche track rat, I have an OEM windshield, because the 15-20 lbs i might shed just aren't worth the risk.

I don't recommend doing the other windows for anything less than a dedicated track car multiple reasons. For one; most polycarb plastics you'll find to do this with will yellow with continued UV exposure. They also don't have the surface hardness, and will pick up a multitude of scratches over time from everything: tiny rock chips, bugs, the ring on your finger when opening or closing the door. Hell, even driving through heavy dust or sand can be abrasive enough. Both of those reasons will cause a surprisingly drastic decrease in visibility after as little as a few months. For two; it's really hard to get them to fit into place solidly and not rattle without riveting the edges all the way around, and I assume you want them to still work. For three, they do not insulate sounds from the outside. Driving a car with polycarb windows on the highway is loud: wind noise, tire noise, other cars on the road, you'll hear all of it. You won't hardly be able to hear the radio. It won't be worth it, I guarantee.

On the topic of overall weight reduction: you might see it if you have a data logger and do before and after runs, but you probably won't really feel it very much, except for the always possible placebo effect. As @lockem said, you'd probably get 30-40 lbs for replacing the windows, maybe another 30-40 for ditching the rear seat. If the seat weighs more than I think and the lexan weighs less than I think, than at most I'd say you're looking at 100 lbs total, from a 3800 lb car, which by my math is only a little over 2%. There's an old racer's rule of thumb that says losing 100 lbs = 10 hp = one tenth of a second off of the 1/4 mile time. In my experience, that seems about right. Another old rule of thumb is that you need to increase a car's horsepower by more than 10% before you'll really feel it seat-of-the-pants. Again, I've messed with this old adage, and it seems more or less accurate, meaning the Giulia needs a roughly 28hp bump to really feel it. So you're looking at the amount of performance increase of a decent intake or exhaust, and less than most available tunes, and most likely not enough to actually feel.

To summarize: Not much weight savings, less comfort, negligible performance gain, potentially less safety.

Edit: i only just now realized in the original post you did specifically say rear windshield, and I was talking about the front. Oops. Oh well, the rest of it still stands.
Definitely picking up what you’re putting down. Logically Leaning Away from the idea now lol. Thanks for the input.
 

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No problem! I'm glad to help. If you're looking for performance, there are a handful of tried and true options that are very heavily discussed on this forum.
 

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Discussion Starter #6
No problem! I'm glad to help. If you're looking for performance, there are a handful of tried and true options that are very heavily discussed on this forum.
Yes I know. Just don’t wanna go catless. Seems like the serious power Gaines all require a downpipe. And the max power pro piggyback doesn’t really have any real references for the power gain.
 

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To be fair, the best way to get 'real power' out of a 2.0 is to sell it for a QV, lol.

You don't have to go full catless, you can get 200 cell racing cats that meet emissions standards but flow better. (don't quote me on this, though, i havent tested it myself.)

I'm not sure about exact numbers, but it seems that 20-30hp is common from the piggybacks. I'd like to see someone do back-to-back dyno pulls, though. I think it is commonly agreed that the turbo is the real choke point for big power from our 2.0T.
 

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I have a
To be fair, the best way to get 'real power' out of a 2.0 is to sell it for a QV, lol.

You don't have to go full catless, you can get 200 cell racing cats that meet emissions standards but flow better. (don't quote me on this, though, i havent tested it myself.)

I'm not sure about exact numbers, but it seems that 20-30hp is common from the piggybacks. I'd like to see someone do back-to-back dyno pulls, though. I think it is commonly agreed that the turbo is the real choke point for big power from our 2.0T.
I have the QV.
 

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There should be no question that weight reduction is the expensive way to improve acceleration performance. However, it is important to note that weight reduction improves braking, cornering, and tire life. It is not just an improvement in acceleration. Getting enough weight reduction to matter usually requires a large number of small modifications. Each modification often requires custom fabricated (== $$$$) parts. For a QV the "low hanging fruit" that I know is the battery and removing stuff you don't need.

I was hoping to find polycarb replacements for the little, fixed, non-critical side windows, more as a way to observe the performance of the material than as a way to shave weight.

I believe that small airplanes can come equipped with bird strike rated polycarb windshields, so the strength and impact resistance of the material should not be in question. However that does mean having the right material designed properly for the application. Curved safety glass windshields are very difficult to break, but once broken they catastrophically lose strength.
 

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There should be no question that weight reduction is the expensive way to improve acceleration performance. However, it is important to note that weight reduction improves braking, cornering, and tire life. It is not just an improvement in acceleration. Getting enough weight reduction to matter usually requires a large number of small modifications. Each modification often requires custom fabricated (== $$$$) parts. For a QV the "low hanging fruit" that I know is the battery and removing stuff you don't need.

I was hoping to find polycarb replacements for the little, fixed, non-critical side windows, more as a way to observe the performance of the material than as a way to shave weight.

I believe that small airplanes can come equipped with bird strike rated polycarb windshields, so the strength and impact resistance of the material should not be in question. However that does mean having the right material designed properly for the application. Curved safety glass windshields are very difficult to break, but once broken they catastrophically lose strength.
You are correct on the performance aspect, but I would also say that the amount of weight reduction needed to get a noticeable increase in lateral g's and braking is about on the same scale as the weight/horsepower/quarter mile time adage. (Using the estimates I quoted earlier, it would take approximately 280 lbs out of the Giulia to make an easily noticeable difference.)

Also, yes, most planes do use a specially created version of polycarbonate as the front viewscreen, and they use an air cannon to fire chickens to test the strength of the window. Commercial aircraft are rated to withstand a bird strike of a four-pound bird at roughly 370 mph. However, it is also extremely thick, typically being 3 to 4 layers and over an inch thick. I was thinking more along the lines of the type of lexan someone would typically use on a car to save weight, which is much thinner and not nearly as strong.
 

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Generally only smaller prop planes use lexan/ polycarbonate windshields. Those windscreens DO NOT have to meet the same safety standards as commercial airliners or small jets or turbojets. Airliners, corporate jets, and many turboprop aircraft have thick glass screens.

I have been flying small planes for over 20 years, and have seen numerous bird strike reports in aviation websites, where the goose, hawk, or even eagle ended up dead inside the cockpit with the pilot. So lexan may not be the way to go for a front windshield.

For example Pilot Blinded in Bird Strike


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You are correct on the performance aspect, but I would also say that the amount of weight reduction needed to get a noticeable increase in lateral g's and braking is about on the same scale as the weight/horsepower/quarter mile time adage. (Using the estimates I quoted earlier, it would take approximately 280 lbs out of the Giulia to make an easily noticeable difference.)

Also, yes, most planes do use a specially created version of polycarbonate as the front viewscreen, and they use an air cannon to fire chickens to test the strength of the window. Commercial aircraft are rated to withstand a bird strike of a four-pound bird at roughly 370 mph. However, it is also extremely thick, typically being 3 to 4 layers and over an inch thick. I was thinking more along the lines of the type of lexan someone would typically use on a car to save weight, which is much thinner and not nearly as strong.
The chicken gun is fun. I've witnessed a couple of tests on empennage where the requirement is an 8lb bird. Lots of blood and feathers!
 
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