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Message: <blockquote data-quote="blown98gt" data-source="post: 521309" data-attributes="member: 11284">In order to select the correct size injector for your application, you might wish to use one of the following formulas.In most cases a naturally aspirated engine will have a B.S.F.C of .50. This means that the engine will use .50 lbs. of fuel per hour for each horsepower it produces. Supercharged engines will want to be at .65 lbs. per hour or higher. Turbocharged engines will want to be at .60 lbs. per hour or higher.(B.S.F.C is brake specific fuel consumption - How much fuel you are using per horsepower per hour)Using these numbers as a guideline, you can select the approximate injector size in the following formula.For your injectors you wont want to run them over 80% duty cycle and this is the accepted industry standard, though you can run them over 80% duty cycle this will shorten the life cycle of the injectors..The formula is the following<img src="http://img.photobucket.com/albums/v673/ryne002/md%20write%20up/form.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />To find the HP value of the of the above mentioned injectors use this formula:<img src="http://img.photobucket.com/albums/v673/ryne002/md%20write%20up/form2.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />So you can see that 8 39lb injectors should hold 496 hp, for a n/a car, a supercharged car will need .65 B.S.F.C. and a Turbo car will need .60 B.S.F.C.Hope this helps you guys out some, and I do want to make sure that you guys understand a few other things that are very important to figure in.  * This is what the injectors should hold on MAX duty cycle  * You should also have more than needed so you are not maxing your fuel system out.  * Your fuel pump also plays a part in this and even though your injectors will hold so much hp on Max duty cycle your fuel pump needs to be able to support the hp and flow rate needed.So just for kicks I figure the most common question, 60lb injectors and 39lb injectors. keep in mind this is for 80% duty cycle but if you/your tuner goes over 80% that is on you guys.60lb Max hp at 80% duty n/a = approx. 768hp (.50)60lb Max hp at 80% duty t/c = approx. 640hp (.60)60lb Max hp at 80% duty s/c = approx. 590hp. (.65)39lb Max hp at 80% duty n/a = approx. 500hp (.50)39lb Max hp at 80% duty t/c = approx. 416hp (.60)39lb Max hp at 80% duty s/c = approx. 384hp (.65)</blockquote>