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#### scott25

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can someone explain why and how 8psi is different in one turbo then to the next? 8lbs is 8lbs isn't? and how to you figure out how much boost should be used from one another... thanksf

#### EnJoiThaRex

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Psi is a measurement of Pressure or restriction. Think of fuel pressure and how a pressure regulator works. As engine speed increases (vacuum decreases) the diaphragm closes to make more of a restriction. More restriction means faster velocity of flow. Another way of thinking is like putting your finger on the tip of hose to make it a thin streamline flow.

The measurement to use in determining how much air is actually flowing is by measuring the mass. The volume is calculated in CFM and you can use that to determine the weight of the volume, or more specifically, its mass which is in lb/ft.

For simplicity i can use 2 rooms as an example. A small room and a big room. Now figuring out the volume of a room is quite simple Lwh=V (length x Width x Height= Vol). With that equation youll see that the larger room will have MORE volume. Now fill the rooms with 100psi of air and hold it there air in it. Which room has more volume of air? The larger room. Now measure that mass of the air, which has more mass? The larger room. From the example we have at a constant 100psi there is more volume resulting in more mass of the larger room

The same is for turbos but you dont use the formula LWH. For pressure using boyles law it. P V=DRT (pressure x volume = Density x R (gas constant) x Temp and then the density formula is D=M/V (Density= Mass/Volume). If you know how to do math then you can change them around. V= (DRT)/P (vol= (Density x R Gas Constant x Temp)/Pressure)
and using the density formula M=D V (Mass=Denisty x Volume)

PSI gets you to the surge line, which can kill turbos. Mass kills motors

#### scott25

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ok cool im beginning to understand a little bit more. thanks, so like ive read before boost doesnt kill motor bad tuning does?

#### EnJoiThaRex

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ok cool im beginning to understand a little bit more. thanks, so like ive read before boost doesnt kill motor bad tuning does?
Bascially, but they all do have some relation to each other. Bad tuning does kill motors, but if your engine internals are not even designed to support the increased cylinder pressures then even with good tuning your still screwed.

But in my opinion "tuning" isnt simply defined to ECU programming.

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