p factor is a resultant of the change of apparent pitch during rotate. When
the rotate occurs, the apparent angle of incidence of the prop blade
increases and takes a bigger "bite" out of the air thus producing a net
torque. This site give a better explanation
http://home.earthlink.net/~x-plane/F...y-PFactor.html

or this one which is essentially identical

http://www.madsci.org/posts/archives...3940.Ph.q.html

"me" wrote in message
om...
"Jim Anderson" wrote in message
...
What's the ratio of the thrust generated by a hi-bypass turbofan between
what goes out the back and the "propeller" effect of the main fan?

Depends heavily upon which engine your are considering. However,
the trend for a long time was towards ever higher ratios. Truely
high bypass engines produce anywhere's from 65% - 85% of their
thrust from the fans.


The main fans rotate in the same direction.

Yes.


How much torque (P-factor from
my flying days in a C-152) do they create?


Can't say for sure. I'd suspect very little.