Formulas and Conversions

Horsepower & Torque

HP = Torque x RPM / 5252

TQ = Horsepower x 5252 /RPM

Engine Displacement

Displacement = #cyl x Swept Volume

Displacement is in CC's

Example: What torque is required to generate 300hp at 6,200RPM?

TQ = 300 x 5252 / 6200 = 254ft/lbs of torque @ 6,200RPM

Example: 4G93 1.8 liter engine

4-cylinders, 81mm bore and 89mm stroke

Disp = 4 x 0.7854 x 81 x 81 x 89 / 1000 = 1834.5cc

Displacement Conversions

Cubic Inches of Displacement to Cubic Centimeters

CID = CC / 16.39

CC = CID x 16.39

 

Choosing Fuel Injectors

Finding injector size required for a certain HP amount (total engine output)

LBS/HR =( [BSFC / (# cyl)] x HP) / Peak Injector Duty Cycle

Example: Cubic Inches of Displacement for a 1834.5cc engine

CID = 1834.5 / 16.39 = 111.9

Example: BSFC = .50, Duty Cycle = 80%, HP target = 200

LBS/HR (per injector) = (.125 x 200) / .8 = 31.25

Fuel Injectors

BSFC = Brake Specific Fuel Consumption. The ratio of fuel consumed (in pounds per hour) to horsepower produced. Simply how efficient the engine is at converting the fuel into power.

Typical BSFC values:

lower values = more efficient

NA = .50 - .55

Turbo = .55 - .60

Methanol = double the previous values

 

Max HP of injectors (lbs/hr) on gasoline

HP = ([Injector Size (lbs/hr) x Duty Cycle] / BSFC) x # of injectors)

Fuel Conversions

CC/Minute to LBS/Hour

LBS/Hr = CC / 10.5

CC/Min = LBS x 10.5

LBS/Hour to Gallons/Hour

GPH = LBS / 6

LBS = GPH x 6

CC/Minute to Gallons/Hour

GPH = CC x .01585

CC = GPH / .01585

Fuel Pump Flow Conversion

LBS/HR to Gallons/Minute

GPM = LBS/HR / 360

Example: HP rating of each injector on a 4-cylinder engine. 19LBS/HR injectors @ 80% Duty Cycle and .50 BSFC

HP per inj. = [(19 x .80) / .5] x 4 = 121.6

Example: LBS/Hr flow rate for a 210cc/min fuel injector

LBS = 210 / 10.5 = 20

Miles to Kilometers Conversion

To convert miles to kilometers, multiply the miles value by 1.61.


Kilometers = miles × 1.61

Kilometers to Miles Conversion

To convert kilometers to miles, divide the kilometers value by 1.61.


Miles = kilometers / 1.61

Example: How fast is 60mph in kph?

KPH = 60mph x 1.61 = 96.6kph

Example: How far is 60 miles in kilometers?

Kilometers = 60 miles x 1.61 = 96.6 kilometers

Example: How fast is 80kph in mph?

MPH = 80kph / 1.61 = 49.69mph

Example: How far is 80 kilometers in miles?

Miles = 80 kilometers / 1.61 = 49.69 miles

Kilowatt to Horsepower Conversion

To convert kilowatt to horsepower, multiply the Kw by 1.34102209.



Horsepower = kilowatt × 1.34102209Hp

Horsepower to Kilowatt Conversion

To convert horsepower to kilowatt, divide the horsepower value by 1.34102209.


Kilowatt = horsepower / 1.34102209Kw

Example: How many horsepower is 130Kw?

Hp = 130Kw x 1.34102209 = 174.33Hp

Example: How many kilowatts is 200Hp?

Kw = 200Hp / 1.34102209 = 149.14Kw

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