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Discussion Starter · #22 ·
GMS carbon rear louver is meant to replace rear trunk glass window only while the rear hood remains OEM, so trunk space is not altered in any way. We are developing the GMS carbon rear hood with integrated ducktail and optional race wing at the moment, so I'm without hood right now to show the exact photo. flank, rear bumper and carbon louver here in the photo are not assembled, they are just put together to get the idea, hence some misalignment. We have moulded the exact shape of OEM glass as a base and then worked the shape of the vents from here on, so the fitment is perfect. I'll provide isntalaltion video once we get the carbon hood done (1 - 2 months).

Tire Car Automotive tire Hood Grille


This mod provides 3 important technical improvements (measured and proved) and visual improvement (personal opinion)
  • Significantly better dissipation of the engine bay heat
  • Reduced drag and lift
  • Reduced weight
The best address for installation would be car glass repair and replacement workshop. It is the same procedure as replacing front windscreen. Removing of OEM glass and then fixing GMS carbon rear louver. Labor should be about 100€, perhaps a bit less.
 

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Discussion Starter · #25 · (Edited)
I intended to keep this private until we finish the protoype, but I guess no harm will be done by sharing some insight. Here is a quick CAD I did to help us with the shaping of the rear hood.

We are currently looking for appropriate rear wing to fit 4C design and desired aero/drag figures.

Font Grass Bag Electric blue Fashion accessory
Human body Sleeve Font Electric blue Personal protective equipment
 

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Would be cool to have a rear hood with the option to get a wing on it for the track and take it off for street use..
I am sorry to disturb this conversation but
thats something we already did almost 2 years ago and that is we sell for over a year. It comes with a bag that you can fit inside the car’s passenger side for transport. There are 4 little covers for the screwholes next to the license plate. If disassembled it is totally invisible. It comes with e replacement part that replaces the car’s aluminum par at the rear from left to the right side. It also comes with inserts that strengthen the cars rear frame so there is no bending in it and all force is delivered to the wheels with no loss. The structural bars you can see are just for increased side bending stability as the leverage effect of the wing supports is pretty high so they move a litte even as they are made from 8mm aluminum. You can leave them out at no risk in case you don’t like the look...

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From the functional view and being nearly totally invisible there is no way of improving this in my opinion. But to be honest it is not cheap in a common view.

Sorry for disturbing. But I thought it might be helpful to know that there is something available if member are desperately looking for a solution that doesn’t change the look of their car while driving on the street.

best regards
Alex
 

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Discussion Starter · #29 · (Edited)
Alex, you're welcome to share your solution here. I am aware that there are a few wing solutions for the 4C on the market already, unfortunately a bit too extreme or not too effective for our needs, so they don't fit most of our requirements.

Here are the requirements we have to fulfill with this project:

Looks:
Wing assembly looking like an OEM part, not too extreme, so hopefully I'll be able to keep it on a car even on a street and not draw too much attention. We plan to drive to the events and back home with the wing on. We are talking about medium sized, low drag, medium downforce, curved wing, to match 4C's appearance.

Downforce and drag:
Wing with up to 1600mm of span and chord of up to 300mm. 3D aerofoil to match the 4C's airstream (roof/cabin section has different airstream than the "clean" air at the side of 4C) with different angle of attack at the center of the wing then at the side of the wing where there is a "clean" airstream in less angled line, so 3D aerfoil instead of 2D. Of course we also need curved shape to fit the car's appearance of curved rear body style (viewed from the top). This is sums it up to a wing with specs. of about 80-100kg of downforce at 160kmh and estimated loss of about 5-9 BHP (clean airflow). We are currently discussing possible solutions with 3 suppliers, with all of them providing detailed CFD analyses, specs and solutions.

Limitations:
Our class regulations in TA Italia (SuperStreet) require the wing to be within the car's boundaries, therefore a curved design is a must to be able to run a decent swing span and not have to mount the wing too much forward, decreasing the leverage on the rear axis. Also all the road cars with factory wings installed have to follow this principle so to drive it on a street without too much of attention we'll follow this rule.

Balance:
We have to follow the limitations above, so we don't want a wing with an downforce we cannot match at the front of the car.

Weight:
We don't want to add the weight to the 4C and especially not to the rear of the car, so carbon fiber trunk will save the weight that we will gain back with the wing and brackets.

Rigidity:
With carbon fiber trunk and integrated duck tail serving as a mounting point, we'll have zero flex.

Alex, do you happen to have the CFD data of your wing and the weight of entire assembly (wing brackets, mounts, reinforcement brackets in the bumper,...), so we can compare where we gain and where we lose? I'm sure that your design must have at least double the downforce of ours, but as mentioned, it doesn't fit our requirements, so we are after a custom solution. Also, do you have any data of lap times of your car with and without aero?
 

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Hi Rudy, you are right that our design is not compliant with some regulations of for example Time Attack. Our approach is that we develop the fastest possible under the regulation of the 24h NBR and other International race serie and than try to do it in a way that you can add it on a street car too.

You are totally right, that the wing alone won’t do any good to the car as you will have massiv understeer. Thats why we always choose a holistic approach and develop everything you need so the components make sense. For example matching with the spoiler we offer the matching splitter. Since last year we even offer a wider carbon splitter that also completely covers the front wheels. That was one of the big problems of the 4C so far. You can combine the carbon splitter with a additional aluminum version below if you are just track focused.
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This is how it looks like in a street version.

without any purpose I once tested the effect without a splitter because we had to remove the older narrow aluminum version at the track after I killed some screws of it on a little excursion offside the racing line 😉😂. The result is as expected. Massive understeer, loosing one second in laptime on our 2,6 Km lap!

Years ago we also tested the removal of the spoiler in Zandvoort as we had top speed issues. To be fair at this time we didn’t had the differential in the car. The result was 3 Km/h more topspeed but two second loss of laptime per lap as the car had massive grip problems at the rear while accelerating out of corners. With the LSD the loss of time will be less.

All other results are difficult to isolate and to transfer on a car with a different set up. My cars are so heavily modified and carry all features we developed. This means they will multiply some of their single effects if used in combination. I assume that the two fastest 4C on a racetrack worldwide a not very unlikely located in my personal garage. Both cars are faster than an current TCR car and also a little faster than a current GT4 car driven by a professional race driver ( winner 2020 Porsche Carrera Supercup, winner 2020 Porsche Carrera Cup Germany and WEC pilot on 991 RSR) on same track.

That is why it is often very difficult for us to compare other honestly really good parts from you and others with what we do. The requirements are simply totally different as some of the problems only occur if you are constantly two, three or more seconds faster per lap.

Wherever I have the chance to use parts of my fellow colleagues like you, I do so. That’s why I for example buy the rear uniballs from you, the front ones from Jamie and also the replacement ball joints. The stock dimension carbon parts I buy from my friend Enrico and we modify them with inserts at the areas we need to.

Reading you explanation I now understand the purpose and restrictions of it. So it makes sense to do it that way for you. Not competing in time attack our solution is probably better if you want to have the least possible modifications to the stock bodywork and keep it look decent if spoiler is not attached.

Regarding the weight I will measure it and post you the single weights. I guess everything combined is probably 8Kg extra weight. On my racecar it is less as we use an weld in aluminum construction to the rear frame. So I think in that case it’s will be about 6,5 Kg extra.

best regards

Alex
 

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Honestly it is very easy to add different functions to our spoiler bracket. You can also attach a bag carrier or luggage case securely to it in case you want to travel longer trips. The holder would be removable in 5 minutes as there are just 10 screws to remove. Another 4 screws and even the bracket is removed and you wont see anything on the car because the 4 covers of the holes next to the number plate are painted in the color of the car. You can even attach a bike carrier instead of the luggage box or base carrier 50s style.

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Something like this is already possible but I think we need to have a system with lights on it as you wont see the taillights and numberplate of the 4C anymore if loaded with bags. Therefore we need to do an auxiliary electric loom with a connector like on towing kits. That’s no problem to do so but til now Marco and I were just joking about this. If anybody wants us to finish this project just let us know... I would suggest to hide the electrical connector behind the numberplate. It is 2 Minutes work to remove the numberplate but if we are willing to invest this time, the system is totally invisible if not in use.

Maybe we should consider marketing that system even without the spoiler as a universal carrier system for the 4C that you can attach all aftermarket carrier systems to it.

I really would like to hear some thoughts from you about this.

Best regards

Alex
 

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Alex,
would there be a weight limit on that rear carrier, how would it affect the cars suspension? I think in the manual the boot has a max load of around 15kg, but this being cantilevered over the back would be more load i think, if my school physics lessons about moments serves me correctly lol
 

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Hi Rudy, you are right that our design is not compliant with some regulations of for example Time Attack. Our approach is that we develop the fastest possible under the regulation of the 24h NBR and other International race serie and than try to do it in a way that you can add it on a street car too.

You are totally right, that the wing alone won’t do any good to the car as you will have massiv understeer. Thats why we always choose a holistic approach and develop everything you need so the components make sense. For example matching with the spoiler we offer the matching splitter. Since last year we even offer a wider carbon splitter that also completely covers the front wheels. That was one of the big problems of the 4C so far. You can combine the carbon splitter with a additional aluminum version below if you are just track focused.
View attachment 114297 View attachment 114298
This is how it looks like in a street version.

without any purpose I once tested the effect without a splitter because we had to remove the older narrow aluminum version at the track after I killed some screws of it on a little excursion offside the racing line 😉😂. The result is as expected. Massive understeer, loosing one second in laptime on our 2,6 Km lap!

Years ago we also tested the removal of the spoiler in Zandvoort as we had top speed issues. To be fair at this time we didn’t had the differential in the car. The result was 3 Km/h more topspeed but two second loss of laptime per lap as the car had massive grip problems at the rear while accelerating out of corners. With the LSD the loss of time will be less.

All other results are difficult to isolate and to transfer on a car with a different set up. My cars are so heavily modified and carry all features we developed. This means they will multiply some of their single effects if used in combination. I assume that the two fastest 4C on a racetrack worldwide a not very unlikely located in my personal garage. Both cars are faster than an current TCR car and also a little faster than a current GT4 car driven by a professional race driver ( winner 2020 Porsche Carrera Supercup, winner 2020 Porsche Carrera Cup Germany and WEC pilot on 991 RSR) on same track.

That is why it is often very difficult for us to compare other honestly really good parts from you and others with what we do. The requirements are simply totally different as some of the problems only occur if you are constantly two, three or more seconds faster per lap.

Wherever I have the chance to use parts of my fellow colleagues like you, I do so. That’s why I for example buy the rear uniballs from you, the front ones from Jamie and also the replacement ball joints. The stock dimension carbon parts I buy from my friend Enrico and we modify them with inserts at the areas we need to.

Reading you explanation I now understand the purpose and restrictions of it. So it makes sense to do it that way for you. Not competing in time attack our solution is probably better if you want to have the least possible modifications to the stock bodywork and keep it look decent if spoiler is not attached.

Regarding the weight I will measure it and post you the single weights. I guess everything combined is probably 8Kg extra weight. On my racecar it is less as we use an weld in aluminum construction to the rear frame. So I think in that case it’s will be about 6,5 Kg extra.

best regards

Alex
💪Looks like an angry 4C! Nice
 

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Alex,
would there be a weight limit on that rear carrier, how would it affect the cars suspension? I think in the manual the boot has a max load of around 15kg, but this being cantilevered over the back would be more load i think, if my school physics lessons about moments serves me correctly lol
The weight limit is probably due to the weak attachment of the trunk and the low load capacity of the car in general. If you are putting two 100Kg + men into the car you are officially not allowed to drive it anymore as you are probably over 1225 Kg of overall weight.

From our side with our track suspension there is non problem as all is designed to take a lot of aerodynamic downforce from the wing already, so anything up to 100 Kg even considering the leverage effect should be fine. But I did not test it so far. It is just theory.

@GMS and @lars
I did not plan to do it. I just said that if someone plans to transport more luggage, two bikes for vacation or a toolbox for the track, it is possible with our system as it is designed to transfer huge loads to a structural strengthened rear frame as an invisible aftermarket solution.

Whoever wants to do that, can do it. Others don’t. The usecase of the 4C is very different from owner to owner. If you want to take it for a long trip, the look of it while traveling from one hotel to the other probably is not the main issue. It is whether to do it or not being able to do it at all.

If you for example want to go to a trackday in Spa and you don’t want to go by trailer, the possibility of transporting your additional toolbox at the rear and the rear spoiler in a bag on the passenger side is something you might want to do.

I am not religious if it comes to a 4C. People should be able to use it for whatever purpose.

Talking about design it is also questionable if the design of the GMS solution is liked by everybody. But that is permanently on the car. It is easy to say something like please don’t put something like this on an italian Sportscars. But that would be wrong in my opinion. I am happy for people having the opportunity to choose between options in comparison to patronize them with my personal view of design or elegance.

So whoever is searching for an opportunity to increase the travel capacity of his 4C nevertheless of an awkward look while traveling with the box now has a chance to speak up. We will do it if somebody wants it...

best regards

Alex
 

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Yeah, but Lexan is a technology of the 1980's.
Heavy, not UV stable (yellows, even the UV stabilized versions become opaque over time), scratches easily, and deforms with the kind of heat that we get in our engine bay.
Polycarbonate these days. Lighter, stronger and UV stable. I would add my name to that list if GMS offer.
It thermoforms also.
 

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@GMS, @4CRacer and others, sorry for a bad explanation. I was thinking of a suitcase that fit in the space left behind when boot is removed:
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Basically, the boot we have, but with a lid, and easy to take out. Maybe this could be combined by making area more open as well, contributing to less trapped heat from exhaust.

So not talking about something that makes my car rear part look like a prolapsed monkeys ass.
 

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Polycarbonate these days. Lighter, stronger and UV stable. I would add my name to that list if GMS offer.
It thermoforms also.
Except, it’s not.
They call it “UV stable”, but that’s more marketing than reality.
Eventually (after 5 years or so), the protection begins to fail and the results are really bad. You get yellowing, milkiness, or what looks like cracking. These are internal to the sheet, and cannot be buffed off. PC is much stronger (vs impact) and lighter than glass of equivalent thickness, but less dimensionally stable than equivalent thickness glass. So the weight can be saved, but needs to be added back in the way of thickness for rigidity. PC also scratches quite easily, though you can get a coating which helps this.

Did some consulting work for the world’s leading manufacturer of polycarbonate sheet in my past. ;)
 
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