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Fuel Injector vs HP Conversion

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Old Nov 3, 2003 | 11:15 PM
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Default Fuel Injector vs HP Conversion

Wondering what a fuel injector rated at 50lbs@ 42psi figures out to at 58psi?

It's 58.7lbs per hour right?
F2 = (√P2/√P1) x F1 or X=(58sqrt/42sqrt)*50
Where F2 is the new flow rate and F1 is the old 50lb and P2 is the 58lbs of fuel pressure now vs the injector rating which is at 42.

And then how much HP will that support @ 115% duty cycle?

Most common turbocharged or supercharged engine configurations run in the .55 to .60 BSFC range right?

So if my injectors are @ 22ms in the 6000 rpm range where does that put the aproximate HP based on the fuel used?

HP = ([INJECTOR SIZE (LB/HR) X DUTY CYCLE] / BSFC)
X (# OF INJECTORS)


So if its 58.7x113/.60x8 thats like 1381 HP... ah ha,,, naugh.... I must have missed someting. Am I doing something wrong or is the math just that far off compared to the real deal? Obviously I'm bored but shouldn't the math be closer???
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Old Nov 3, 2003 | 11:22 PM
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Uhhhhhh
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Old Nov 3, 2003 | 11:46 PM
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your calculation for the new flow rate looks good but that 50# injector is probably rated at 43.5psi(i think)

your off on your duty cycle thinking though. when you are at 100% duty cycle the injector is open ALL the time, you can't be open more than all the time. the comuter may ask it to be open for 22ms but it only has 20ms between cycles(at 6000rpm).

to be safe and leave yourself with a little room for error you should use 80%duty cycle, some injectors start to get wierd after 85% and have unstable flow rates.

using your formula that puts the numbers at

((58.7 x .80)/.60) x 8 = 626hp

that is very conservative but if your buying injectors i say be conservative and go big especialy if you are going forced induction.
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Old Nov 3, 2003 | 11:53 PM
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i just realized you are trying to figure you hp based on fuel consumption. in that case go with 100% duty cycle and .55BSFC(probably still high for a blower)

((58.7x1.00)/.55)x8= 853hp

you are using enuff fuel to feed a 853hp engine
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Old Nov 4, 2003 | 07:40 AM
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Originally Posted by parish8
i just realized you are trying to figure you hp based on fuel consumption. in that case go with 100% duty cycle and .55BSFC(probably still high for a blower)

((58.7x1.00)/.55)x8= 853hp

you are using enuff fuel to feed a 853hp engine
Thats sounds closer.. The extra 13% was only part of my error then.

Thanks
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