Hi .
Ok maybe I´m not software-smart enough to get my data sending/recieving problem as fast as needed.
So I try to switch to parallel communication.
I like the instruction:

PortB = VAR (byte)

the only problem is the fact that I need Portb.0 for the external interrupt so I will take the PIC16F873 which has more pins. Still need the ZIF socket for my programming adapter.

I will tell how that works.

To Skimask:
yes you are right about your detonation assumptions.
Know a bit about engines myself : http://www.davidpower.de/fotos_mot.htm