Ken and Ed Anderson.
Your info and advice is well recieved and
timely for me - I didn't know what to use, now at least I can talk
with some knowledge to suppliers.
One small question if I may - what is the fuel
rail pressure usually?
Thanks again!
George ( down under)
Hi Jerry and George,
The debate over the optimal injector size has been going on for
years. I personally plan to use 400cc/38 lb or 440cc/42 lb Ford
injectors. According to
http://www.maxcooper.com/rx7/how-to/fuel_system/calcs.html 38
lb injectors at 80% duty cycle / 43 lb / .5 BSFC pressure are good for
242 HP. The 440cc/42 lb injecors are good for 267 HP.
Also check out RC Engineering which is the most accepted expert that I
know of (
http://www.rceng.com/technical.htm#WORKSHEET).
Using the same assumptions the 38 lb injectors are good for 242 HP and the
42 lb injectors are also good for 267 HP. Looks like these guys are
using the same formulas - good to see consistency from 2 different
sources.
Lastly, note that injectors should not be run continuously over 80%
duty cycle or they will overheat and fail. A smaller is better when it
comes to idle control. DO NOT forget this part of the equation.
Lastly, at cruise altitudes the injector cycle rate decreases as the HP
requirement decreases so at 8000 ft the duty cycle of the injectors will
only be 60 % which is very safe for sustained operation. Call me if
you want to discuss this. Go play with the calculators posted above
(which George has already done).
Ken Powell
Bryant, Arkansas
501-847-4721