Fuel injector is gonna be required for any given engine combo, ie: stock 24 lbs, mild 355, 30 lbs, etc... Do you just go with a small one, see what duty cycle you're injector is putting up with and adjust from there? Or is there an actual formula?

Thanks.

 

There are numerous online calculators for injectors. The basic equation is fairly simple, and will get you in the ballpark. Just about all of them use a brake specific fuel consumption (BSFC) of 0.50 #/HR/HP for a nomally aspirated engine, and recommend limiting duty cycle (DC) to 80% (0.80).

(flywheel HP X BSFC) / (# cyl X DC) = injector required

Example:

(400 HP X 0.50) / (8 X .80) = (200) / (6.4) = 31.25 #/HR

A well tuned race engine might approach a BSFC of 0.45 or better. A nitrous or blower engine might need 0.55, a turbo application might be even higher. Some injectors will accept a DC of 0.90 better than others, but the conservative values used in the example above are the best place to start.

 

Excellent, that's exactly what I needed. Thanks Fred!