Settings:
1920x1080 (Full Screen)
& Vsync Off (primary only for checking if SLI works)
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GPU Scaling:
Before: GPU1= 98% GPU2= 10%
After: GPU1= 98% GPU2= 98%
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SLI compatibility bits:
0x03480005 (Ridge Racer Unbounded, Battlefield: Bad Company 2)
=> in this case/tutorial just for info...
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Proof:

0. Download [www.nvidia.com] & install the latest NVIDIA Driver
1. Download[www.guru3d.com] & open NVIDIA Inspector[/i]
(note: also extract "CustomSettingNames_en-EN.xml")
1.1 Go to Driver Profile Settings

2. Under Profiles you choose => Ridge Racer Unbounded
2.1 & click Add application to current profile

2.2 here you select your Wreckfest.exe
(C:\Program Files (x86)\Steam\SteamApps\common\Bugbear Entertainment\)

3. Hit Apply Changes
& enjoy Next Car Game: Wreckfest with SLI enabled.

i5 2500K @4500MHz
GTX 460 SLI @840MHz / 2000MHz
16GB DDR3 @1600MHz
120GB SSD
Win 8.1 Pro 64bit

Tested on the following NVIDIA Drivers:

• 337.50 Beta
  
• 337.88 WHQL
  
• 340.43 Beta (2nd monitor produced win8.1 bluescreen)
  
• 340.52 WHQL
  
• 344.11 WHQL
  
• 344.65 WHQL

Note: If you got only 1GB VRAM => set Texture Quality to "medium", or you'll get a 50%fps loss!

Unfortunately after installing a new Nvidia Driver, you might have to set your SLI Profile again!
(Even with the Express Installation...)

=> BUT you can "prevent" that by exporting all customized profiles & import them back after the new Nvidia Driver is installed!

Attention No.2:
In the game launcher check the following:

• Ambient Occlusion
  
• Antialiasing
  
• Dynamic reflcections
  
• Enable vertical sync

=> otherwise you'll notice massive flickering!
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In some specific constellations, you'll notice a "texture flickering" bug.

• Sneek Peek => fun-object surfaces flicker
  
• sometimes the car roofs flicker (rare)
  
• sometimes only the excavator, next the track - flickers

Maps without flickering:

• Race: Speedway Oval "bright day"
  
• Derby: Mudpit "bright day"

Another bug I noticed:

• A connection error (or very long lag) during an online race disables SLI somehow.
  => fixed as soon you've returned to the main menu...

Remember:
As this is an EarlyAccess Game, the videocard driver, nor the game engine, haven't been perfectly optimized, yet!

Before @45,4fps
After (SLI Fix) @89,5fps
Before @50,4fps
After (SLI Fix) @96,8fps
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PLZ Rate if you like... :)

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