Probably came from the fact that the formula for injectors calculates 170hp.
Inj. Size(lbs/hr) X Duty Cycle / BSFC = HP per injector.
280cc / 10.5 = 26.6 lbs/hr
26.6(lbs/hr) X .80(80%dutycycle) / .50 (b.s.f.c) = 42.6(hp per injector)
42.6 X 4(number of inj) = 170.6hp
Ow. I think I hurt myself.
Of course I'm just repeating information I've found. I personally don't know what I'm talking about.