splitting fir

At what point is it taking the chunk out?
If it is taking it out in the center, I would suggest taking multiple shallow cuts until you get to where you want to be. as far as depth.
If it is on the end as the bit comes out of the piece, try "pushing" the piece with a scrap piece of wood, and it will not create the tear out on the good piece, but on the scrap piece, instead.

Baggy, What brand of router is this? Try using your highest speed and take off no more than 1/4" of material per pass. If you are rounding all 4 edges start on one of the ends and cross cut first using a push block to reduce tear out. Another possible cause is using the wrong feed direction. You should be pushing your stock from the right side towards the left side. Remember the router is upside down so the feed direction is reversed. I am not familiar with Samona as a brand. Does the bit spin without vibration? A dull or poor quality bit could also be your problem.

Thanks for the replies
The router is a cough cough new ryobi (going to get the hitachi m12v in a few weeks) and I am feeding from right to left and quite slowly ( maybe 1.5"/sec at the most), the bit is new and supposed to be good quality and there doesnt seem to be any bad "vibrations" from the bit or router. This size of bit isn't supposed to be run at speeds greater than 15,000 rpm (supposedly). I will try making 3 cuts instead of the 2 I have been doing. Fir is a cantankerous wood at the best and the grain is always reversing itself. I am also making a 4" relief cut on the ends of my stock before flipping the stock around and running it thru full length. I wonder if the ryobi doesn't have the power and the rpms are dropping too much? Can one get carbide bits resharpened?

Carbide bits can be sharpened, the number of times depends on how much has to be removed to gain a good edge. High quality bits like Whiteside can be sharpened more than economy bits. No reason to cough over a Ryobi router. They are good general purpose machines. You may be asking more than it is capable of with the Fir. Try taking more light cuts to get to your depth, that may get you through your job.