PS4 game: „project cars“ http://www.projectcarsgame.com/
the steering wheel from PS4, the logitech GT force feedback,
does not work with PS4, natively..BUT

„Cronus Max plus“-device from http://cronusmax.com/
is the solution, to get „every“ input device working with PS4.

to order in germany use:
http://www.controller-tuning.de/Cronus/

its your own decision, to use your existing wheel further, or buy a new PS4 compatible racing/steering wheel

at first i did not got it to run.. so its not plug and play..
but with several resources from internet, cronus forum and youtube vids, and a bit of luck
i got it running..

i used a laptop (core2 duo 1,8GHz, 3GB, SSD, windows 10 (32-bit)),
install driver for the logitech racing wheel,
http://support.logitech.com/product/driving-force-gt#download
this driver package works for the old PS2 GT wheel too!
install and calibrate the racing wheel…
take a sheet of paper, paint the wheel with all its buttons, and name the buttons.
now we need a usb hub,
connect to usb hub to pc,
connect the racing wheel to the hub,
connect cronus max plus with its sideway mini usb to the usb hub,
do not connect anything at the end of cronus max plus.. leave it free,
connect the cronus max plus adapter with ps4
download and start the cronus max (http://cronusmax.com/cronuspro/),
start the cronus software,
tools -> cronus update (v1.0, 2015-02-15)
tools -> firmware update
plugins -> plugin manager -> X-AIM Plugin, install
tools -> Options -> Device -> output protocoll:PS4, Configurations:Slot Recall selected,
start the X-AIM plugin using plugins -> X-AIM

choose the ps4 controller
save new profile, name it as you want, choose your aplce to save it,
we will use direct input method,
the GT racing wheel nether occured as input device(left screen) in the device panel, but after mapping the device panel rightside screen displays our button pushes,
DI enable – works only when you have selected the GT wheel in the menu „xxxx“
device panel, push buttons of your steering wheel and see which Var is displayed… and note this on your paper sketch now… do this for all buttons, wheel, pedals..
these Vars we need to map to the ps4 controller now..
right click the white squares and select DI input, select from list the correspondent Var,
when you have all wheel buttons/wheel/pedals mapped save your profile!

a tip: you can map additional keys, i mapped additional inout, mouse input left click to the PS4 controller X-Button, this is usefull in PS4 menu.. do this later if you recognize an advantage og this tip

there is a tiny bug..
sometimes steering left/right, the PS4 ingame wheel is stuttering… and button pushes are reflected as the button pushes where done rapidly serveral times in one row..
then i have to close the PC software of cronusmax and open again..
then it works fluid..

i use it without force feeback.. if this it possible to map, i dont know, there options in the game and in the cronus max software

finaly it works ;o)

PS:
cronusmax does many things more.. use additional keyboard to place insane combos to a single keyboard-keystroke, or playing ego shooters with mouse and keyboard,.. and others more

next steps.. get head mount device like cmoar/auravisor or PS4-VR