4-banging

**You may know this already but I thought it would be useful to post**
This information is taken from the 2004 Edelbrock Sport Compact Catalog Issue.


INJECTOR SELECTION FORMULAS

Formula for converting from LB/HR to CC/MIN
CC/MIN = LBS/HR x 10.5

*Note on injector duty cycle:
Final engine configuration, a 90% duty cycle is acceptable.
Complete new engine build, use 80% duty cycle as a safety factor.
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To find the Max HP value of the injectors from (LBS/HR) on gasoline.
HP = [(Injector Size (LB/HR) x Duty Cycle) / BSFC] x # of Injectors.

*BSFC = Brake Specific Fuel Consumption
General: .50 to .55 BSFC
FI or SC: .55 to .60 BSFC
Methanol: 1.10 to 1.20 BSFC
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Injector Size per HorsePowa
In general, if you use BSFC = .50 and an acceptale duty cycle of 85% on a 4 cylinder engine, then:
LBS/HR = HP / 6.8

Example:
You plan to make 240 HP. What size injectors should you use?
LBS/HR = 240 / 6.8
LBS/ HR = 35 LB/HR (use conversion formula to find cc/min)
CC/MIN. = 368 cc/min
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OTHER FUEL FLOW FORMULAS:

Convert CC/MIN to LBS/HR: CC/MIN / 10.5

Convert LBS/HR to GPH: LBS/HR / 6

Convert CC/MIN to GPH: CC/MIN * .01585


...and finally
FORMULA FOR COMPRESSION RATIO

CR = Cyl Volume @ BDC / Cyl Volume @ TDC
= 1 + (Swept Volume / Volume @ TDC)
= 1 + [(0.7854 x Bore x Bore x Stroke) / 1000] / (CCV + HGV + PDV)

CCV = Combuston Chamber Volume in cc's.
HGV = Head Gasket Volume in cc's.
= Head Gasket Compressed Thickness in mm x 0.7854 x Bore x Bore / 1000
PDV = (Piston Deck Volume) + (Piston Dome Effective Volume)
= (0.7854 x bore x bore x Deck to Piston Distance) / 1000 + (Volume of Piston Depression - Volume of Piston Bumps)

Example:
What is CR of an engine if the heads have 42cc chambers, head gasket is compressed to 1mm and flat top pistons give 0.5mm deck clearance at TDC?

HGV = (1 x 0.7854 x 81 x 81) / 1000 = 5.2cc
PDV = [(1.5 x 0.7854 x 81 x 81) / 1000] + 0-0 = 2.6cc

CR = 1 + [(0.7854 x 81 x 81 x 87) / 1000] / (42 + 5.2 + 2.6)
= 10.0 CR
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Feel free to add...