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| TECH CENTER - Tech Discussion - EFI System Formulas
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TECH DISCUSSION
EFI SYSTEM FORMULAS
FORMULA FOR INJECTOR SIZE SELECTION
| LBS/HR = ((BSFC ÷ # CYL'S) X HP) ÷ PEAK
INJECTION DURATION |
Example: What size injectors should
you use for a Super Victor EFI 600 hp
350 cid Chevy?
Lbs/Hr = ((0.50 ÷ 8) x 600) ÷ 0.85
Lbs/Hr = 37.5 ÷ .85
Lbs/Hr = 44
FLOW RATE CHANGE BY
PRESSURE REGULATOR CHANGE
F2 = New flow rate (lbs/hour or cc/min)
F1 = Old flow rate (lbs/hr or cc/min)
P2 = New Pressure
P1 = Old Pressure
An adjustable fuel pressure regulator allows you
to change the amount of fuel delivered per unit time from the injector. Any changes affect the fuel curve globally, so re-mapping the idle and light load
conditions is usually necessary. The mass flow is
proportional to the square root of the pressure ratio:
Example: You have a 28 Lb/hr (@45 psi) injector. How much will it flow at 60 psi?
F2 = (√60 ÷√45) x 28 Lbs/hr
F2 = (7.746 ÷ 6.708) x 28 Lbs/hr
F2 = 32.3 Lbs/hr
MAXIMUM HORSEPOWER SUPPORTED BY A GIVEN INJECTOR
| HP = [(INJECTOR SIZE (LB/HR) X DUTY CYCLE) ÷ BSFC] X (# OF INJECTORS) |
Example: How much power can be supported by eight 28 Lb/hr injectors?
HP = [(28 Lb/hr x 0.90) Ö 0.50 Lb/HP hr] x 8
HP = 50.4 HP x 8
HP = 403
TO CONVERT CC/MIN TO LBS/HR
Please Note: The above equations and rules apply only to four-cycle engines. The equations have been simplified for ease of understanding. Answers will be approximate but generally will be close enough for use as a guideline.
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