Throttle Body Sizing

[Terry Faugno]

At 02:31 PM 7/26/96 PDT, you wrote:
>At 01:15 PM 26/07/1996 UT, you wrote:
>>
>>
>>What is VE ?  (Volumetric Efficiency)
>
>So,  if I have this right, then as the piston moves to BDC on the intake
>stroke it results in a particular volume opening up;  displacement of the
>individual cylinder.  If this is, for example, 50cc, then 100% VE means that
>at BDC the pressure inside the cylinder is the same as atmospheric pressure?
>
>ie:  50cc of air/fuel has been drawn into the cylinder?
>
>Would lower values mean that there was still a slight vacuum in the
>cylinder?  ie:
>
>VE% = pressure inside cylinder at BDC
>     -------------------------------  * 100
>     atmospheric pressure
>
        As I was taught in college auto tech class, VE is this:

actual fuel air mix in cylinder
-------------------------------   * 100
total possible fuel air mix

For example, at the end of the intake stroke, in a 100CC total volume
cylinder, if you have 75CC of fuel/air mix, then that is 75% volumetric
effeciency. Some engines have their intakes tuned such that at certain
RPM's, it resonates and can achieve better than 100% VE, like 105% or so.
Typically NASCAR uses this technique.

                Terry