[Diy_efi] Pressure readings perpendicular to airflow

[Greg Hermann]

At 11:02 AM 6/3/03, Grant Beaty wrote:
>> A probe perpendicular to the flow measures "static" pressure. Yes, static
>> pressure goes lower as velocity goes up in an adiabatic flow.
>
>Doh, I should have known that.
>
>> A probe directed into the flow will measure 'total' pressure--which is
>> equal to dynamic (velocity) pressure plus static pressure.
>>
>> A change in velocity converts part of the static pressure into dynamic
>> pressure or vice versa.
>>
>> Greg
>
>Hmm, Corky's book seems to suggest that measuring static pressure is valid
>(from his testing methods on pade 165), while Humphie's book says "The
>pressure ratio is obtained from the outlet total absolute pressure divided
>by the inlet total absolute pressure, and represents the actual pressure
>ratio from compressor inlet to outlet devoid of any ducting losses. Total
>pressure is the sum of the measured static pressure plus the dynamic head."
>on page 65.
>
>So an intercooler reduces the dynamic pressure (through cooling and reducing
>velocity) while ideally keeping the same static pressure correct? The quote
>from Automotive Turbocharging & Supercharging Systems just doesn't seem
>right to me. Isn't the total pressure a constant from one side of the turbo
>to the other (if we ignore how much the compessor heats up the air)?
>
>Thanks,
>Grant Beaty

Nope--you lose static pressure going through ducting and/or an intercooler.

Greg
>
>
>>
>>
>>
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