I'm sorry, but I'm out of ideas. I can't see any reason why it wouldn't work and from what I can see in the code, that release does support PWM for the x-racer.

Hopefully, someone who has the same receiver will see this thread.

how the channels mapped on radio???

Is AETR1234, i played with letters of AETR but nothing changes.
I think i have to do something else in an 8 channel receiver, because this AETR1234 works well for a 4 channel receiver. 

My best advice would be to buy a modern FrSky receiver that has s.bus output.

It will be much smaller than the one you have, all the channels are on a single wire and the update speed is much faster than a PWM receiver.

Yes i think is the a good idea.
Something like X4RSB or the new R-XSR Rx with a XJT or R9M module.