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Forced Induction

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Forced Induction

Choosing a Turbo

Sizing

CFM

Compressor Maps

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Turbo height compared to Sump oil level (dry sump)

Oil line feed to the Turbo (T-section, turbo fitting, pipe diameter)

Oil drain from turbo (fitting, larger pipe, foamy oil, garvity drain, deep sump, to rocker covers)

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The following equations are taken from the Turbomania book with the values for my engine substituted. Please refer to the Turbomania book for more detailed information.

Engine Size - 2056cc 71mm Stroke x 96mm Bore

Engine Type - Four Stroke

Maximum RPM - 6000

Maximum Turbo Boost - 10 psi

---------------------Boost Pressure + Atmospheric Pressure *
Pressure Ratio = ------------------------------------------------
-------------Atmospheric Pressure *

10psi boost + 14.7 Atmospheric Pressure--------------------------
-------------------------------------------------- = 1.68 Pressure Ratio
14.7 Atmospheric Pressure----------------------

Density Ratio vs. Pressure Ratio chart (to go here)

To convert the engines volume from cc to cid:

2056cc-------------------------
----------- = 125.4 or 125 C.I.D.
16.387*-------------------------

*cc to C.I.D. conversion factor

1/2 C.I.D. x Maximum RPM---------------------------
-------------------------------- x V.E. x D.R. = C.F.M.
1728*------------------------

(* C.I.D. to Cubic Feet Conversion Factor)

1/2 x 125 x 6000-----------------------
-------------------- x .80 x 1.40 = 243 CFM
1728------------------------

So for my engine:

CFM = 243
Pressure Ratio = 1.68

Converting CFM to lb/min

CFM x 0.070 = lb/min

243 x 0.070 = 17.01

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Knowing the pressure ratio (1.68) and the amount air that my engine will flow (17.01 lb/min or 243 cfm) I can check these values on different compressor maps.

Compressor maps

Garrett T3 40 Trim