

Edelbrock Performance Tech Discussion 

Optimizing your car's performance requires more than just throwing a bunch of parts under the hood. Understanding the relationship between various systems and the mathematical computations necessary to determine which parts will give you the performance you want is key to improved performance in today's factorytuned cars. Use the info in this section to help you select the correct parts for your application. If you have any questions, give a call to our tollfree Factory Tech Line: 18004168628.  
POWER PACKAGE PERFORMANCE LEVELS (5)  


MILE PER HOUR AND REVOLUTIONS PER MINUTE
First find the vehicle speed, MPH and the consequent engine RPM operating range: 

FORMULA FOR MPH
MPH = TIRE RADIUS ÷ 168 x ENGINE RPM ÷ GEAR RATIO Example: What MPH at 6500 RPM with a 4.9 rear axle and 14 inch radius tire in 4th (1:1) gear?MPH = 14 ÷ 168 x 6500 ÷ 4.90 ÷ 1 = 111 MPH Example: In 3rd gear (1.34)? MPH = 14 ÷ 168 x 6500 ÷ 4.90 ÷ 1.34 = 83 MPH Note: Tire Radius is distance, in inches, from center of wheel to the top of the tire. Note: Gear Ratio is Rear Axle ratio divided by Transmission Gear ratio. 

FORMULA FOR RPM
RPM = 168 x GEAR RATIO x MPH ÷ TIRE RADIUS Example: Using the first example, what will be the RPM after shift from 3rd to 4th gear at 83 MPH?RPM = 168 x 4.90 x 83 ÷ 14 = 4880 RPM 

FORMULA FOR GEAR RATIO (GR)
GEAR RATIO = TIRE RADIUS x RPM ÷ 168 ÷ MPH Example: Using the first example, what Gear Ratio is required for 120 MPH at 6500 RPM?GR = 14 x 6500 ÷ 168 ÷ 120 = 4.51 

FORMULA FOR TIRE RADIUS
TIRE RADIUS = 168 x MPH x GEAR RATIO ÷ RPM Example: Using the first example, what tire radius for 110 MPH but at 6000 RPM with a 4.11 gear?Tire Radius = 168 x 110 x 4.11 ÷ 6000 Tire Radius = 12.7 inches Note: Approximately a 25" diameter tire. Remember that the tire radius will be less during hard acceleration than when the vehicle is standing still. Also, radius will be greater at high speed due to tire expansion from centrifugal force. 

DISPLACEMENT, VOLUMETRIC (VE) EFFICIENCY, AND CFM  
FORMULA FOR VOLUMETRIC (VE) EFFICIENCY
VE = (CFM X 3456) ÷ (CID X RPM) If VE (volumetric efficiency) is less than 1 (or 100%) the amount and quality of charge in the cylinder is reduced so less torque is produced. VE above 100% is a supercharging effect and more torque is produced. 



FORMULA FOR CID (cubic inch displacement)
CID = NUMBER OF CYLINDERS x SWEPT VOLUME Note: CID = N x 0.7854 x bore x bore x stroke (all in inches)Example: What is CID of a V8 with a “30 over”, 4 inch bore and 3.48 inch stroke? CID = 8 x 0.7854 x 4.030 x 4.030 x 3.48 CID = 355 cu. inches 

FORMULA FOR CFM
CFM = CUBIC FEET PER MINUTE A measure of air flow into and out of an engine (CFM = CID x RPM x VE ÷ 3456).Example: What CFM is consumed by a 355 CID engine at 4500 RPM if VE = 105% (1.05)? CFM = 355 x 4500 x 1.05 ÷ 3456 CFM = 485 Example: What CFM by the same engine at 6400 RPM if VE has fallen to 95% (0.9)? CFM = 355 x 6400 x 0.95 ÷ 3456 CFM = 625 

TO CONVERT C.I.D. TO CC'S
C.I.D. = CC ÷ 16.39 Example: What is the cubicinch displacement of a 5000 cc engine?C.I.D. = 5000 ÷ 16.39 C.I.D. = 305 

TO CONVERT CC'S TO C.I.D.
CC = C.I.D. X 16.39 Note: cc = cubic centimeter, 1,000 cc = 1 literExample: What are the cc’s of a 350 C.I.D. engine? cc’s = 350 x 16.39 cc’s = 5736.5 Please Note: The above equations and rules apply only to fourcycle 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. 

COMPRESSION RATIO  
FORMULA FOR COMPRESSION RATIO (CR)
CR = CYL. VOLUME @ BDC ÷ CYLINDER VOLUME @ TDC CV = CLEARANCE VOLUMECR = (CV + SWEPT VOLUME) ÷ CV CR = 1+ SWEPT VOLUME ÷ CV CR = 1+ (SWEPT VOLUME ÷ VOL @ TDC) CR = 1+ (0.7854 x BORE x BORE x STROKE) ÷ (CCV + HGV + PDV) CCV = Combustion Chamber Volume, in cubic inches Note: if volume is given in cc’s then ÷ 16.4 to get cubic inches. HGV = Head Gasket Volume, in cubic inches, HGV = Head gasket compressed thickness x 0.7854 x bore x bore PDV = (Piston Deck Volume) + (Piston Dome Effective Volume) PDV = (0.7854 x bore x bore x deck to piston distance) + (volume of piston depressions  volume of piston bumps) CV = CCV + HCV + PDV Example: What is CR of the engine in #9 if heads have 72 cc chamber, head gasket is compressed to 0.040 inch and flat top pistons give 0.025 deck clearance at TDC? Please Note: The above equations and rules apply only to fourcycle 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. 

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 = (√P2 ÷ √P1) x F1 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 remapping the idle and light load
conditions is usually necessary. The mass flow is proportional to the square root of the pressure ratio:


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
DIVIDE CC/MIN BY 10.5 Please Note: The above equations and rules apply only to fourcycle 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. 

PRESSURE AND FLOW  
PRESSURE CONVERSION FACTORS  


Example: You have 15 in Hg (inches of Mercury) at idle. How much is this in Kpa?
Kpa = 3.386 x 15 Kpa = 50.8 

FLOW BENCH CONVERSION FACTOR
CFM = CFM x √(28 ÷ P) Typically flow bench values are given for a pressure drop of 28 in H2O. To convert flow figures from a different pressure drop to 28 in H2O use the formula above.Example: You have flow figures of 152 cfm at 10 in H2O. What if the same head was flowed at 28 in H2O? CFM = 152 x √(28÷10) CFM = 254 cfm Please Note: The above equations and rules apply only to fourcycle 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. 

FUEL SYSTEM REQUIREMENTS  
BRAKE SPECIFIC FUEL CONSUMPTION
Brake Specific Fuel Consumption is the ratio of fuel consumed (in lbs. per hour) to horsepower produced. This ratio is a direct indicator of how efficiently the engine converts fuel into power. Most factory gasoline type engines run approximately a .50 to .55 Brake Specific Fuel consumption (BSFC) range while a highly efficient normally aspirated race engine operates at approximately a .40.45 BSFC.
These factors should be considered when sizing & selecting injectors for your particular application. LBS/HR = HP X BSFC Generally BSFC = 0.50.Example: How much fuel flow will you need to feed your new 440 hp ETec EFI crate engine? Lbs/hr = 440 x 0.50 Lbs/hr = 220 GPH = LBS/HR ÷ 6.0 Example: What is the GPH for the 440 hp crate engine?Lbs/hr = 220 ÷ 6 Gals/hr = 37 Please Note: The above equations and rules apply only to fourcycle 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. 

CFM RULES
CFM and Carburetors:
CFM and Manifolds:
CFM and Camshafts:
CFM and Cylinder Heads:
CFM and Exhaust:
CFM and Engine Control:


EFORCE BOOST MEASUREMENT  
Installing A Boost Gauge Or Pressure Tranducer
1. The TMAP sensor mounted on top of the manifold at the rear of the driver's side, outputs a 05 volt signal through pins 1 & 2 (pin 1 is signal & pin 2 is signal return,) that can be converted to an absolute pressure reading using the below calibration curve. Use of this signal requires an ambient pressure correction for calculating boost pressure. 



2. The second option is to utilize the pressure port at the rear of the passenger side intake runner flange. Your supercharger has been predrilled and tapped for a 1/8" NPT fitting. There is currently a plug sealing the hole, which can be removed, and replaced with a fitting to adapt to your sensor.  
CAUTION: Never cut into the vacuum lines leading to the fuel rail pressure sensor and bypass actuator, on the driver's side of the manifold, for the purpose of tapping in a boost gauge. Interruption of the vacuum signal to the fuel rail pressure sensor can affect the fuel pressure reading to the PCM, which can result in engine failure! Furthermore, this port reads pressure before the intercooler, and therefore is before the inherent intercooler pressure drop. Readings from this port will always be approx. 20% higher then what the engine actually sees.
If measured properly on an otherwise stock 4.6L Mustang GT, your boost readings, utilizing an electronic transducer or MAP sensor, on a dyno, should be comparable to this boost curve, shown below, collected from a recent dyno test here at Edelbrock. If you install a mechanical boost gauge in your vehicle, you will see a steady 5 PSI on the gauge during full throttle acceleration on the street. 



EFORCE TMAP INFORMATION FOR FORD & BOSCH SENSORS  
If you are using a custom calibration for your GM based EForce application you will need the following TMAP information in order for the Manifold Absolute Pressure and Intake Air Temperature parameters to read correctly.
To help determine which sensor you have you can look at the serial number. If your superchargers serial number is between 1 and 1611 your system will have the Ford TMAP, unless you have a Z06, all Z06 applications use the Bosch TMAP regardless of what the serial number is. The Ford TMAP will be attached to the supercharger housing with 2 bolts. If your superchargers serial number is 1612 or greater your system will have the Bosch TMAP. The Bosch TMAP will be attached to the supercharger housing with 1 bolt. 

Ford TMAP Sensor Information
For EForce Superchargers with Serial number 0  1611 (other than Z06, all Z06 applications use the Bosch TMAP) 

NOTE: If you have a 2005 LS2 the offset cannot be below 0, so just use 0 and it will be fairly close.  
MAP Sensor Linear: 223.43 kpa  
MAP Sensor Offset: 7.88 kpa  


Bosch TMAP sensor information
For all Z06 applications and GM EForce Superchargers with Serial number 1612 and greater 

NOTE: If you have a 2005 LS2 it will limit the Linear to 255.9 and the offset can't be below 0 so just use those values and it will be fairly close.  
MAP Sensor Linear: 268.9 kpa  
MAP Sensor Offset: 1.65 kpa  
NOTE: The stock IAT values should be fairly close, if they are not you can use the values below.  


EFORCE THROTTLE BODY COMPARISON
Edelbrock EForce (85mm) vs. Ford Mustang GT twin (55mm) and GT 500 twin (62mm) Stock twin 55mm bore with 10mm shaft = 5.66 sq. in. total area GT500 twin 60mm bore with 10mm shaft = 6.91 sq. in. total area Edelbrock single 85mm bore with 8.8mm shaft = 7.64 sq. In. total area In addition, area being equal, a single bore will always flow better than a twin bore because there is less bounding surface area to interrupt the flow. Also, both the stock GT throttle body and the GT500 throttle body have an as cast surface leading into the bores, where the Edelbrock unit is machined through for less wall friction. Last, the inlet is port matched to the throttle body for a perfect matching transition. 
