In late May, I said I'd be revisiting the GT4 Mk2 wing with the arrival of my used Vorsteiner CSL trunk and subsequently launched a limited group buy for Connex members.
Silvano at CarbonProduction GmbH then let me in on a new modern design he had been working on in the last few months. The design is directly inspired from BMW Motorsport's latest technology with a few tweaks.
But first, some history:
The BMW Motorsport Design Origins.
The Ancestor: the E92 M3 GT4, sort of.
The E92 M3 GT4 was initially introduced without a wing as BMW still hadn't released the M3 GTS. They had already planned on offering the E9X M3 GTS 122cm carbon wing for the GT4 customer race car.
From the street to the track: wrong way.
The pre-2007 era of street car aero development was limited to wings and smoothened underbodies. The stock body E92 M3 wasn't exactly an aerodynamically efficient body.
The GTS aero package of its lowered right height, extended lower splitter and trunk wing worked together to eliminate lift experienced with the OEM aero body.
The GTS wing provided a +53 kg delta at the rear over the stock body in combination with the front GTS chassis mounted 5 piece lip.
It wasn't enough.
Most GT4 Customer Racing cars were also fitted with the Genuine BMW Motorsport GT4 lip which extends further outwards than the GTS lip.
"A rule of thumb in aero: the front always works in tandem with the rear."
The GTS wing board wasn't enough, it proved too small for motorsport use.
BMW had to rapidly revised its design.
They first introduced the E9X M3 GT4 MK1 carbon wing with a wider carbon wing board of 130cm and standard GTS mounts.
Here's Peter running that wing at full Angle of Attack.
There were supposedly still complaints about rear end lift.
Higher and wider did the trick.
They introduced the E9X M3 GT4 MK2 carbon wing board of 140cm and extended risers to extend beyond the dimensions restricted by street legislations.
It proved better suited for the circuit and provided superior stability compared to the GTS.
The M235iR Customer Racing Car.
BMW introduced the M235iR in 2014: it was designed to fill a gap in BMW's customer racing program as an entry-level racing car after the end of production of the E92 M3 GT4 and prior to the release of the F8X M4 GT3, GT4 and M2 CS Racing car.
The M235iR was used in series and events such as the VLN Endurance Championship and the Nürburgring 24 Hours on the Nürburgring.
For reference, the M235iR started at 59,000 euros whereas the E92 M3 GT3 started at 121,000 euros.
The car was the usual BMW Motorsport recipe: stripped out interior with bucket seats, roll cage, safety gear, improved suspension, brakes, wheels & tires, racing electronics (ABS, DSC, TC) and limited-slip differential.
What was out of the norm for its modern entry level racing cars was the introduction of a revised widebody design and aerodynamics.
The EVO WING.
BMW Motorsport visibly learned from the E92 M3 GT4 Customer Racing Program and introduced the M235i Racing Car with the EVO aero package from the start.
The learnings of a wider wing board using high risers were carried over from the MK2 GT4 wing.
The board design was updated over the GT4 MK2 with a slightly recessed area in the middle of the board.
The wing was further designed with a specific trunk engineered with reinforcement plates for the Evo wing.
Here it is in prototype stage.
From the track to the street:
the M4 GTS rear wing.
BMW M's introduction of the M4 GTS touted its increased engine performance thanks to its water injection system and they deemed the carbon strut brace as the highlight of the car.
"Many arguments can be made about the timing of BMW M's slide into ///Marketing, this might be one of them."
Following on the E92 M3 GTS recipe, the M4 GTS featured an adjustable front splitter and rear wing.
This time around they adapted the BMW Motorsport track version from the M235i Racing Customer Car.
They used the same wing board yet revised the end plates to a smaller, less aggressive design and mounted the wing quite lower using the bottom section of the M235i Racing prototype risers.
The Final Evolution:
the M240i Customer Racing Car.
2018 saw the final evolution of the EVO wing as we know it today with the introduction of the M240i Customer Racing Car.
Relevant to this topic was the introduction of new end plate designs over the M235iR.
The end plates were larger and more aggressive. They retained the 3 holes for adjustable angle of attacks.
It's safe to assume BMW Motorsport optimizes for performance and performance alone.
Or do they.
In BMW's own words:
"The BMW M240i Racing Evo package contains, among other things, optimised engine software. New end plates for the rear wing contribute to the optical upgrade of the cars used in race series and Cup classes around the world."
Unfortunately that might be where it gets diluted.
This brings us to the core of this journal entry:
Silvano's M240iR Carbon Wing.
Differences versus OEM
Silvano designed the wing with a few revisions compared to BMW Motorsport's original design.
1. Wing mounts bolted to the board versus within.
The mounts to which the risers are bolted to are themselves bolted to the wing board.
The wing board comes with the riser mounts pre-installed by Silvano at the CarboProduction.DE factory using titanium hardware to reduce weight.
The high mount risers is nearly a 1:1 design as it pertains to shape and adjustability. There is a slight CNC machining programming change on the cuts within the risers and to clear the bolts on the board.
The risers retain the adjustable bolt holes to adjust on the wing mount.
This bolt location shows the least aggressive AOA setting.
2. Complete naked carbon end plates vs OEM painted.
The OEM EVO wing comes with end plates in a black painted finish. Silvano's end plates are naked carbon.
It gives you the option to have them painted if you seek to mimic the OEM EVO design or customized to match body colors.
Another small touch from Silvano is the use of black titanium hardware with a shaped washer.
A small, but nice detail.
3. Rubber seal to carbon board.
The wing board is made from pre-preg carbon fiber cured in autoclave. The same carbon manufacturing process as OEM.
Silvano the lays the pre-preg carbon layers in a pattern that allows to create a seam under the front of the board.
That seam is sealed with a rubber joint to improve durability of the wing and reduce cracking probabilities.
4. Finish Options
The OEM EVO wing was purely available in Gloss clear coated finish.
Silvano offers a few options:
Raw carbon fiber (as pictured on my photoshoot)
This is straight out of the mold and is the lower end of finish quality. You can see the slight finish imperfections in the gel coat and an orange peel appearance.
Gloss Clear Coat
Just like OEM. The finish quality is superior to raw carbon as the clear coat is wet sanded and polished to remove imperfections and achieve a mirror finish.
Matte Clear Coat
The aftermarket thing! Less chemical resistant than gloss, matte sure looks amazing and remains a 2 component hardened clear coat.
You can see the orange peel and lower gloss level above.
The top of the board has more careful attention to the gel coating process.
5. No specific trunk or reinforcement plates.
The wing is deemed as universal. Silvano does not offer reinforcement plates specific to any chassis for it.
If you will fit this to an F8X / F2X car, you can use BMW's genuine reinforcement plates for the trunk from my understanding.
For E9X, E46 or any other chassis, you would need to have reinforcement plates made by your local machine or body shop.
P.S.: I write these to the best of my knowledge and research, with my own narrative spin to it. If some technical information is incorrect, feel free to comment the needed corrections!