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Old 02-19-2010, 10:09 AM   #1093 (permalink)
Silo
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Join Date: Jun 2009
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Quote:
Originally Posted by RCZ View Post
Also, guys, the whole bigger turbo makes more power thing.... From what I understand its not because it flows more, we know that 5psi is 5psi. What matters is the charge density of that 5psi.
That was my point. A larger turbo, and i have to state more specific, at a given psi might be more efficient, which means will it heat the charge less, hence more oxygen in that charge.

Quote:
Originally Posted by RCZ View Post
According to what Silo posted, a turbo that is in its peak efficiency zone (or island if you've ever seen a turbo flow chart) will create a more dense 5psi than one that is not. Think of it this way... colder air is denser, air particles are more compact therefore there is more oxygen to burn therefore you make more power. The same apparently goes for a turbo operating at peak efficiency vs one that isnt. The one operating at peak eff. somehow produces a more dense charge (at the same temperature) as the one that is out of its efficiency zone. The post by silo didnt explain why, but I have a feeling it has something to do with how the air is compressed in a more efficiently sized tc than a less efficiently sized one. Efficiency relating to the size of the engine and the amount of psi you are targeting.
One simple factor is that it has to "shovel" less. You have a larger shovel you will dig that whole more efficiently than with a spoon. The other factor might be that the exhaust side is larger and therefore pumping loss is reduced. The larger turbo might still be less efficient at a lower psi but usually we compare the peak operating psi range.
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