intake design v1 8

Quick Intake Design Calculator v1.8Independent Throttle Body TuningBy Stefan Vince

For use with ITB induction or plenum type induction with very large plenum sizes ( > 1 x engine capacity).

Bore: 103.25 mmStroke: 90.932 mm

Rod length: 155.52 mmPort C/L length: 0 mm

Peak HP RPM: 6900Intake cam

duration (0.050"): 280 degIntake air

temperature: 37 deg C98.6 deg F

Suggested Runner Diameters. Suggested Runner Areas.Minimum: 45.3 mm Minimum: 1610.9 mm^2

1.78 in 2.497 in^2Best: 46.2 mm Best: 1674.4 mm^2

1.82 in 2.595 in^2Maximum: 47.1 mm Maximum: 1743.3 mm^2

1.85 in 2.702 in^2

Suggested Runner Mach Numbers at Peak HP RPM.Minimum: 0.502

Best: 0.483Maximum: 0.463

Suggested Runner Entry Diameter/Area For Tapered Runners.Best: 61.4 mm Best: 2961.9 mm^2

2.42 in 4.591 in^2

Suggested Runner CFM at 28"H2O For Peak HP RPM.246.0 (At 100% VE)270.6 (At 110% VE)295.2 (At 120% VE)319.8 (At 130% VE)

Suggested Runner Lengths.1st Harmonic: 895 mm (Total: 895 mm)

35.25 in (Total: 35.25 in)2nd Harmonic: 501 mm (Total: 501 mm)

19.71 in (Total: 19.71 in)3rd Harmonic: 358 mm (Total: 358 mm)

14.10 in (Total: 14.10 in)4th Harmonic: 287 mm (Total: 287 mm)

11.28 in (Total: 11.28 in)5th Harmonic: 239 mm (Total: 239 mm)

9.40 in (Total: 9.40 in)

Suggested Peak Torque RPM Using 2nd Harmonic.5245 TO 5745

Base Engine Data

Calculation Results

Notes.Peak torque rpm is based on 2nd Harmonic intake length only and will be affected by other factors than the intake length alone and so actual values could be lower or higher than calculated values. Intake length calculations are based on NACA-TN-935 by Boden et al and the work of Prof. G. P. Blair. Diameters based on mean runner speed of 73-79m/sec (240-260ft/sec). Suggested runner CFM from David Vizard's "How to Build & Modify Cheverolet Small-block V-8 Cylinder Heads".

At Peak Piston Speed - Mach number should be 0.500 or less for the runner diameter being used or choke in the port will occur.

D14

If 0.050" checking height figures are not available either measure cam duration or deduct 40-50 degrees from advertised duration as starting point.

D16

For typical street type systems use a figure that's 2-3 x ambient temp. With ram air/cold air induction, temps would lower. Carbon fibre/plastic intakes on racing cars can get close to ambient temps.

C34

Runner entry diameter for tapered runners is from the best flow coefficient found from NACA-TR-933 by Grey et al. Best nozzle diameter ratio was found to be 0.75 for low included angles. The inverse of this is 1-1/3 and is used as the multiplyer.

Calculation Results

Notes.Peak torque rpm is based on 2nd Harmonic intake length only and will be affected by other factors than the intake length alone and so actual values could be lower or higher than calculated values. Intake length calculations are based on NACA-TN-935 by Boden et al and the work of Prof. G. P. Blair. Diameters based on mean runner speed of 73-79m/sec (240-260ft/sec). Suggested runner CFM from David Vizard's "How to Build & Modify Cheverolet Small-block V-8 Cylinder Heads".

Quick Intake Design Calculator v1.8Resonance TuningBy Stefan Vince

For use with OEM style plenum manifolds for EFI and Turbo.

Natural frequency ofIntake air temp: 40 deg C total intake system: 57.7 Hz

Runner average dia D1: 37.2 mm Natural frequency ofTotal runner length L1: 245 mm runner only: 347.0 Hz

No. of runners: 4Runner tuned rpm

1

(2nd harmonic): 9713 to 10113Plenum volume V: 1.8 Litres Runner tuned rpm

Zip tube dia D2: 63 mm (3rd harmonic): 6515 to 6915Zip tube length L2: 1000 mm Runner tuned rpm

(4th harmonic): 4877 to 5277Runner Spacing

0

Total system uppertuned rpm: 6720 to 7120

2

Total system lowertuned rpm: 3260 to 3660

Inputs Results

Notes.Tuned RPM values are derived from SAE 820407 by Ohata et al, SAE 2006-01-3653 and SAE 2007-01-1399 by Brennan et al. Calculating the natural frequency of a total manifold system is not entirely accurate. Higher accuracy is obtained with simple plenum designs. The more complex a manifold system is the more chance it's actual natural frequency will be higher or lower than the calculated values. The only accurate way of finding the natural frequency of a total manifold system is by performing a frequency sweep using CFD or by using the actual manifold and using acoustical methods (loudspeaker and microphone) to determine at what frequency it will go into resonance.Tuning values for the total manifold are dependent on the runner spacing and internal geometry of the plenum. Close runner spacings will dampen or cancel frequencies excited by single cylinder frequency and be excited by multiple cylinder frequencies and their harmonics. Large runner spacings will dampen or cancel some multiple cylinder frequencies whilst allowing excitation by single cylinder frequencies. The user is referred to the above SAE papers for more details.*Use the I.T.B Tuning worksheet to determine initial runner lengths and diameters*

Less than port spacing

Port spacing or greater

Runner bellmouth?

Zip tube bellmouth?

Quick Intake Design Calculator v1.8Throttle Body Sizing.By Stefan Vince

Maximum RPM: 6500 Intake air density: 0.173 lb/ft^3Engine Displacement: 1998 cc's Intake air velocity: 163.4 ft/sec

122 ci'sNumber of Cylinders: 4 Average CFM demand: 230.6 CFM

Peak CFM demand: 230.6 CFMVolumetric efficiency: 100 %

Throttle body size: 58 mmIntake air temp: 104 Degrees F 2.3 inches

40.0 Degrees C Throttle body mach no: 0.140Intake air pressure: 21.5 Psi

1.48 BarCompressor or

intercooler flowrate: 40 lb/min

Throttle CD value: 0.836

Pressure drop: 0.5 Psi

Coefficient of Discharge Calculator.

Throttle body size: 57 mm Throttle body size: 65 mm2.24 inches 2.56 inches

Throttle shaft dia: 6 mm Flow bench [email protected]" H2O: 509 CFM0.24 inches

CD: 0.836 CD: 0.788

Inputs Results

Area Method Measurement Method

Notes.This spreadsheet uses simplified calculations and that greater accuracy would be obtained by using formulas for compressible flow through orifices and accurately determined CD maps.

C8

For ITB (independent throttle body) or one choke per cylinder equiped engines, set this to the cylinder volume.

C10

For ITB (independent throttle body) or one choke per cylinder equiped engines, set this to 1.

C12

80 - 100% for production engines (2 valve 85% - 4 valve 95%). Race engines can be up to 125 - 130%.

H13

For more than one throttle use the following to determine size: 1. Square throttle body size. 2. Then divide by the number of throttles you have. 3. Then find the square root of that value and that will be your throttle size. E.G. If a 3" TB is recommended but two throttles are required - 3^2=9sqin. 9/2=4.5. sqrt of 4.5=2.12" - so two 2.12" throttles are required.

H15

This should not exceed 0.528 or choke will occur

C16

Use 0 psi for N/A engines. Enter gauge or compressor map pressure for turbo/supercharged engines.

C19

Use 0 lb/min for N/A engines. Enter compressor map or calculated intercooler values for turbo/supercharged engines.

C21

Set at 0.8 if value unknown. Use CD calculator to determine values for existing throttle body.

C23

Normally set to 0.737 psi. Can go lower for fuel injected engines, 0.5 psi pressure drop is common. Weber or Dellorto carbs use 1.473 psi minimum.

H31

Corrected to standard temp and pressure - 68 degrees F and 29.92 inches Hg.

Quick Intake Design Calculator v1.8Bellmouth Design.By Stefan Vince

Runner diameter: 37.2 mm

Runner area: 0 mm^2Runner circumference: 0 mm

Hydraulic diameter: #DIV/0! mm

1

Major axis: 37.2 mm Major axis: 37.2 mm

Minor axis: 18.6 mm Minor axis: 24.8 mm

Radius R: 7.4 mm Radius R: 7.4 mm

Inlet diameter: 74.4 mm Inlet diameter: 86.8 mm

Area ratio: 4.0 :1 Area ratio: 5.4 :1

Minimum centres: 92.3 mm Minimum centres: 104.7 mm

Inputs

Results

Type A Type B

If the runner is non-circular it’s hydraulic diameter needs to be calculated and used to determine the

major and minor axis of the bellmouth.

Runner diameter Hydraulic diameter

Notes.This worksheet is used to design bellmouths for runner entries. They are both based on ASME nozzle/bellmouth design principles and both have Cd values of over 0.95. Type A works well up to ~Mach 0.65 and is quite compact. Type B is more efficient and works up to ~Mach 0.95 but is limited to larger runner spacings. Bellmouth profiles are elliptical and can be easily drawn using CAD or traditional drafting methods. Always make a template to check the internal profile.

intake design v1 8

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