28" of water is one psi. For fully developed tubulent flow, the flow is
proportional to the square root of the pressure drop, so it is easy to
convert from one pressure drop to another.
Randall wrote:
>>When heads and manifolds are flowed, you can use any pressure you want. I
>>use 7" because it makes the math easier, and also because of the max
>>capabilities of my flow bench vacuum source. However, to compare to
>>readings taken by other flow benches or on other products, there
>>must be a
>>common standard vacuum for comparison purposes. The 'industry'
>>has settled
>>on 28" of water.
>>
>>
>
>Thanks, Jack, Ron & others who responded.
>
>28" still seems high to me, after all that's roughly 1/10 of the total
>pressure you have to stuff air into the cylinders, and there's still the
>drop through the carbs and valves to consider. I guess the industry is
>mostly interested in big numbers and, as usual, doesn't care if those
>numbers actually mean anything.
>
>Randall
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