injector equation

[struckinc]

is there an equation that i can use to determine what size injectors i am going to need for my new engine? i am not sure how to figure that out. or if someone knows already that would help too. i am working on a na/ka that will have about 280-300hp at the crank. not sure which injectors will be best for that application. also what kind of fpr should i go with? thanks

[struckinc]

sorry about the above post. i found the equation. i figure i need 440cc injectors to efficiently run this engine. my question now is what effect will running my stock injectors with an adjustable fpr and a walbro 255lph have on the engine FOR NOW? i know i wont get max hp out of the motor with stock injectors but engine has gone a little overbudget and i wasnt really ready to order bigger injectors and the bikirom yet. i can deal with losing some hp for now i just didnt want the injectors to max out and run too lean

[rogoman]

The OEM injectors will max out and you'll be running lean; not good as the motor may start detonating. Also since the OEM injectors are ~270cc/min, they're up in the 90% duty cycle in that power range and can easily heat up.

[180fan]

don't push injectors past 80% they can start to act goofy at that point.

[Q45tech]

Idle is usually the problem with larger injectors and with reduced psi to 34, the injector gets derated 34/43.4= 0.7834 then square root = 0.885 or 11.5%.You cannot use a lower than 34 psi pressure and many times the idling opening time is the minimum, so with larger injectors you must live with too rich [plug fouling] or a much much higher idle speed.

[struckinc]

i have the walbro fuel pump and the z32 fuel filter. so will i still have a reduced fuel pressure? my concern was how will the stock ecu prog. treat the larger injectors. esp if i bump the fuel pressure with an adjustable fpr?