Fuelling is bookkeeping. The engine has decided how much air it will take; your job is to supply the matching mass of fuel, reliably, at every load point. Two ideas make the whole category legible: lambda and duty cycle.
Lambda is air-fuel ratio expressed as a fraction of stoichiometric for whatever fuel you are burning, so lambda 1.00 is chemically correct whether that is 14.7:1 on petrol or 9.8:1 on E85. That is why tuners talk in lambda: the target does not move when the fuel does. Convert to AFR only when you need to talk to a gauge that reads in AFR.
Duty cycle is how much of the time an injector is open. Size injectors so peak demand sits at or below 80%, and you keep headroom for cold starts, poor fuel and next year's power target. Size them so peak demand is 95% and you have built in a lean condition at exactly the moment it hurts most. The flow you need follows from power, BSFC and cylinder count — not from what fits the manifold.
Ethanol changes both numbers. E85 needs roughly 30-35% more fuel volume for the same air, so injectors and often the pump have to grow, but its knock resistance and charge cooling buy back more than they cost on a boosted engine. Pump "E85" varies by season and region, which is why blending to a known target beats trusting the label.
FAQ
Should I tune to AFR or lambda?
Lambda, whenever you can. It normalises across fuels, so a lambda target stays valid when you switch between petrol, E85 or a blend. AFR numbers only mean something once you also state which fuel they refer to.
How do I convert lb/hr to cc/min?
For gasoline, multiply lb/hr by about 10.5 — a 52 lb/hr injector is roughly 550 cc/min. The exact factor depends on fuel density, but 10.5 is the industry-standard conversion. Also check the test pressure the rating assumes, usually 3 bar.