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Old 05-14-2018, 10:02 PM   #17284
chevota84
 
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Name: chevota84
Title: Too Much Time
Status: Not Here
Join Date: Jul 2009
Location: Prineville, OR
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Posts: 4,926
Quote:
Originally Posted by biggy238 View Post
1:1 has no basis in thrust values, unless you want to get all engineer level and calculate surface area acted upon on.

Opinion: 1:1 ratio has no basis in fact. The mass having work imparted to it and the mass imparting the work are only loosely connected by the turbine shaft. You would have to calculate enthalpy of the exhaust gas stream across the turbine, and calculate the power needed to flow/pump inlet air at any given point of operation. Pressure alone is far from an indicator of the efficiency of the turbocharger as a system. Calculate power in vs power out.

I would like to read if someone has published information to contradict my opinion. I've never had a reason to look in to it either way. I just (think I know) the energy available to the turbine and what's being imparted into the inlet air mass are so wildly different that it's not reliable to use pressure.

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A lot of that is over my head, however, wouldn't the 1:1 ratio lead you to believe that the forces are close to balanced? If the turbine housing is too tight or the wheel is too small, you'll see a much higher drive pressure number vs boost, the same if there's an intake restriction. When it gets a higher than 1:1 ratio you're seeing an inefficiency on one side or the other of the turbo, it's taking way more power than its producing.

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