Guys, some interesting reading here. It's a much more civilized thread about AMD graphic higher CPU overhead in DX11 and some glimpse of DX12 benefit for AMD GCN GPU.
I only install graphic driver and CCC anyway.

HBM !! boom! First GPU with HBM... (finger cross is not FLOP)

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Didn't play the game yet, my gran turismo 6 is sitting in dusts....

A tahiti owner states that increasing the power limit to something like +20% helps alot in project cars. Same with people using overclocked 290s

So guys, if you planning to play pCars with your AMD card right now don't bother. I don't know what Slightly Mad did for the past 2 months when they announced the 2nd delay to "polish" the game but the it is unplayable right now compare to older build. Wait for the game update or new driver.

 
Gold release vs older March build | Same graphic settings
 
Gold | 27 FPS | Low GPU usage

 
 
March build (forgot which build) | 56 FPS | High GPU usage

Huh? Got performance problem meh?    Seems running quite smooth on my no OC 280X @ catalyst 14.12.
1080, high, 8xAF, MSAA, low motion blur (anything more is kinda pointless), medium particle (still TONS of water splashing from car in front @ rain)



More:

I think can't be fixed, it's widely discussed that the game physics engine relied on Physx, something the CPU bottlenecked heavily. The only way it can be improved is if the developer rewritten the codes or having a lower overhead OS drivers from microsoft and AMD (amd to lesser extent).

Or if somebody managed to make CUDA to OpenCL wrapper for radeon cards.

this tweak still works?   the last nvidia driver able to do this is like ages ago.

DIRT RALLY FTW 
and its alot cheaper than Pcars atm.
well, i mostly skip PO now and wait for full review then only buy. better to lost out the PO bonus than scratching my head hard to get it to play at a playable fps.

too much cutting inside/rock/bump.
am surprise r290 can easily get 60fps 1440p at all ULTRA except texture and shadows at high. (wheel cam).

R9 280X losing out to GTX760.

R9 290X(!) losing out to GTX770.

Unseen83, i guess you can go to car dealership tomoro.

Project Cars PC sales only managed 7% of their total sales... PS4 is their main platform with 60+% sales.

I read bohemian think its cool to tied client fps to server fps.
Some hardcore sim racer I knew use like more than rm10k worth of custom racing wheel, pedals, shifter, handbrake and still use hd7850 for that same rig.

Nah, i'm just their certified backmarkers.
Usually for GPU/games benchmark Kotaku show result from TweakTown site.

*Sim

Link in my siggy, you can join if you ready to be humiliate got steering wheel.
We don't play arcadey. 
Nah, most of hardcore sim racing games is not quite graphically intensive and some is really old. (rFactor, rFactor 2, GSC, iRacing, Richard Burn Rally)
You can try my settings and use the x86 executables. Keep AI below 20 for optimum perf. You can reduce track details for moar FPS.
I get 40-ish on race start with 21 AIs and 70+ everywhere else at Nords, some tracks got crazy dips though.