How to calculate necessary injector size

[mhubble91]

Ok, I thought this would seriously help some fellows out there who are really confused with injector sizes. Bigger is not better. Nor will it improve performance at all, unless you require more fuel... More Fuel = Need for more air... Turn that boost up

*To determine the correct flow rate for forced induction applications (turbo'd):

- Find Boost/Pressure Ratio (PR) -> (boost to atmospheric pressure ratio)

PR = 14.7 + Manifold Pressure (how much boost you're pushing)

________diveded by___________

14.7 (atmospheric pressure)


- Now calculate CFM ( VE = volumetric efficiency, use 0.9 for 90% - for most boosted motors)

CFM = Engine Size (C.I.D.) x RPM (optimal power RPM - use redline) x VE x PR

______________________ diveded by_______________________

3456


*C.I.D. can be calculated by multiplying the engine Liters by 61. (ex. 2.0L = 122 CID ... whereas 5.7L = 350 CID)

Now that both Pressure Ratio (PR) and CFM have been calculated, the correct injector size can be estimated. Fine tuning the injector flow with fuel pressure adjustments will still have to be accomplished when the fuel system installation is complete.

Injector Size lbs/hr. = CFM x 0.44298

_____divided by_____

# of Cylinders

Now take this number and multuply by 10.5 and there you have it... you're correct CC injector size

Also, All i can say is be very realistic when doing this... do not say you're redline is 8k when its a stock SR

Cheers

[mhubble91]

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