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10x injector rating means that you would be at 100% of the duty cycle of the injector at the 240 hp point. It's probably a better idea to size your injectors so that they aren't at 100% for any length of time. I would plan on using injectors that are at 85% of the max duty cycle.
Like Sappy says, BFSC is an educated guess. For gasoline powered engines BFSC is around .45 (very lean) to .60 (very rich). For actual operation .45-.5 is probably more realistic. During wide open throttle operations you want to be on the rich side, so on a turbo-charged engine .6 BFSC is a good conservative guess.
I know you don't want to hear about formulas but sometimes it's the best way to understand this stuff. You can use the following formulas to give you a ballpark idea what size injectors you should use and what HP you would be capable of.
Fuel Injector Duty Cycle=HP*BFSC/#of injectors/(injector lb/hr)
If you dyno'd the engine and knew the exact horsepower output you could plug the number in and see exactly what your injector duty cycle is at that max HP. Since you don't know what the HP output of the engine will be you can switch the formula around to find out the HP the 36# injectors will give you at 85% duty cycle:
Max HP = 36#*6cyl*.85dutycycle/.6BFSC = 306 Max HP, a conservative estimate that puts you close to your 300HP goal without worrying about exceeding the 100% duty cycle of the injectors. Probably something GM figured when they supplied the 36# fuel injectors in the L67 at 8 PSI.
Like Sappy says, BFSC is an educated guess. For gasoline powered engines BFSC is around .45 (very lean) to .60 (very rich). For actual operation .45-.5 is probably more realistic. During wide open throttle operations you want to be on the rich side, so on a turbo-charged engine .6 BFSC is a good conservative guess.
I know you don't want to hear about formulas but sometimes it's the best way to understand this stuff. You can use the following formulas to give you a ballpark idea what size injectors you should use and what HP you would be capable of.
Fuel Injector Duty Cycle=HP*BFSC/#of injectors/(injector lb/hr)
If you dyno'd the engine and knew the exact horsepower output you could plug the number in and see exactly what your injector duty cycle is at that max HP. Since you don't know what the HP output of the engine will be you can switch the formula around to find out the HP the 36# injectors will give you at 85% duty cycle:
Max HP = 36#*6cyl*.85dutycycle/.6BFSC = 306 Max HP, a conservative estimate that puts you close to your 300HP goal without worrying about exceeding the 100% duty cycle of the injectors. Probably something GM figured when they supplied the 36# fuel injectors in the L67 at 8 PSI.
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