Mr. Gasket 8703 Hot Rod Calculator - Manual (Page 48)

46 —
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Carburetor size — Based on RPM, engine Displacement
and Volumetric Efficiency
Building off of the previous example, you want to calculate your
user-defined Carburetor Size based on a known vE value.
Suppose through your experience and knowledge of your 1968
Pontiac GTo’s engine specs and modifications, you know you
can reach a vE of 95%.
KeysTroKe disPlay
3. Enter your user-specified VE of 95%:

eff%
Vol
95.
%
4. Calculate the Carburetor Sizes:

User
Carb siZe
593.75
CfM
**

THeor
Carb siZe
625.
CfM

sTreT
Carb siZe
531.25
CfM
 *
raCe
Carb siZe
687.5
CfM
* Repeated presses of  will toggle through the inputs and outputs,
starting with the entered VE.
** Notice the User Carburetor Size appears first in the output. This
Carburetor Size is calculated using the entered VE value of 95%. As
previously mentioned, you are not likely to find an exact size of 594 cfm.
volumetRIC effICIenCy
volumetric Efficiency (vE) is the actual measured airflow capac-
ity at a particular RPM divided by the theoretical airflow capacity
at the same RPM. vE is generally expressed as a percentage.
To calculate the vE of your vehicle, you need to know a few
things. First, you need to know your actual measured airflow ca-
pacity at maximum speed or maximum Torque (a local dyno shop
can help you with this if they have an air-flow meter), as well as
your Engine Displacement.
(cont'd)
UG8703E-B-inside.indd 46 3/3/2010 3:03:59 PM