Small Block Head Flow Chart
The key here is.....”pitot style”.
Not all benches are this style.
Neither of the benches I’ve had are that style.
Both of mine are the orifice plate style(like a SuperFlow SF-600), which compare the flow through the head to an orifice of a known flow value.
(If the orifice is 300cfm, and the inclined manometer reads 50%, you’re flowing 150cfm)
Since both sides of the orifice are operating with the same baro pressure...... it’s not supposed to impact the results.
For example, on a high air pressure day, the pressure is trying to push the air through the head...... but that same high pressure is working against the air as its trying get out of the bench.
The rise or fall in pressure helps one side of the orifice...... and impedes the other side.
My old SF-110, that I bought new and had for 14 years and did countless tests on.......whenever I used the calibration plate, and let the temperature differential between the two sides of the pumps stabilize at about 30*....... the reading on the manometer was always the same.
The pitot style bench isn’t comparing to anything, it’s trying gauge what the actual flow of the air is through the flow tube.
And, in order to know what the flow is...... you need to know what the air density is.
So, the weather matters.
I bought this bench new in 2007.
The key here is.....”pitot style”.
Not all benches are this style.
Neither of the benches I’ve had are that style.
Both of mine are the orifice plate style(like a SuperFlow SF-600), which compare the flow through the head to an orifice of a known flow value.
(If the orifice is 300cfm, and the inclined manometer reads 50%, you’re flowing 150cfm)
Since both sides of the orifice are operating with the same baro pressure...... it’s not supposed to impact the results.
For example, on a high air pressure day, the pressure is trying to push the air through the head...... but that same high pressure is working against the air as its trying get out of the bench.
The rise or fall in pressure helps one side of the orifice...... and impedes the other side.
My old SF-110, that I bought new and had for 14 years and did countless tests on.......whenever I used the calibration plate, and let the temperature differential between the two sides of the pumps stabilize at about 30*....... the reading on the manometer was always the same.
The pitot style bench isn’t comparing to anything, it’s trying gauge what the actual flow of the air is through the flow tube.
And, in order to know what the flow is...... you need to know what the air density is.
So, the weather matters.
I bought this bench new in 2007.