FJBen
SILVER Star
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- #981
So onward we go.
Again this all a moving target as pressure, cfm etc change with temp/humidity/elevation as stated earlier. What you find out is not all turbo makers publish compressor maps, not all compressor maps are even in the same format. Some are cfm, some are lbs/min, some are kg/s. A little more math that you thought you would never use will get you going. Most are in lbs/min so lets convert that.
410cfm should be around what the engine needs at 22psi and 3400RPM.
conversion to lbs/min I've found many formula's, but in reality it's again based on actual temp/density. A few turbo publishers use .069 ~ .071 so I'm going with that.
410cfm x .069 = 28.2lbs/min
Lets take a look at some maps of turbos people have thrown out to work here on mud. THe GT2052R is one that has been used in 3B kits with good reports.
Again I'm using around the max flow the 13BT needs at 3400rpm.
Garret GT2052R
So what this is showing us is that Pressure ratio on the "Y" ratio. I'm using 2.5 to get my desired 22psi. The "X" axis is the lbs/min the engine needs, in my case 28lbs at 22psi at 3400rpm.
So that topographic map looking area is where the turbo flows air and how efficiently it does it at the pressure ratio. Those are called efficiency islands. (from a site): The efficiency of a turbocharger is measured by its ability to compress the air without adding excessive heat. The higher the efficiency, the cooler the outlet temperature for a given boost pressure (it will still be above ambient temperature). So ideally you want to be in the middle, the most efficient.
Too far to the right of the map and the turbo will choke out meaning turbo speeds will increase greatly and efficiency goes down quickly. Garret states this line is at 58% or below efficiency. Air stops flowing correctly, heats generated and damage to turbo can occur. Lots of heat = bad.
Too far to the left of the map is the surge line. From garrett: Operation to the left of this line represents a region of flow instability. This region is characterized by mild flutter to wildly fluctuating boost and “barking” from the compressor. Again bad, damage to turbo can occur. Too much air, no where to go.
So looking at the GT2052R, it's going to be choking out big time at 22psi. At lower boost numbers it will be OK, but will run out of air to push rather quickly.
Again this all a moving target as pressure, cfm etc change with temp/humidity/elevation as stated earlier. What you find out is not all turbo makers publish compressor maps, not all compressor maps are even in the same format. Some are cfm, some are lbs/min, some are kg/s. A little more math that you thought you would never use will get you going. Most are in lbs/min so lets convert that.
410cfm should be around what the engine needs at 22psi and 3400RPM.
conversion to lbs/min I've found many formula's, but in reality it's again based on actual temp/density. A few turbo publishers use .069 ~ .071 so I'm going with that.
410cfm x .069 = 28.2lbs/min
Lets take a look at some maps of turbos people have thrown out to work here on mud. THe GT2052R is one that has been used in 3B kits with good reports.
Again I'm using around the max flow the 13BT needs at 3400rpm.
Garret GT2052R
So what this is showing us is that Pressure ratio on the "Y" ratio. I'm using 2.5 to get my desired 22psi. The "X" axis is the lbs/min the engine needs, in my case 28lbs at 22psi at 3400rpm.
So that topographic map looking area is where the turbo flows air and how efficiently it does it at the pressure ratio. Those are called efficiency islands. (from a site): The efficiency of a turbocharger is measured by its ability to compress the air without adding excessive heat. The higher the efficiency, the cooler the outlet temperature for a given boost pressure (it will still be above ambient temperature). So ideally you want to be in the middle, the most efficient.
Too far to the right of the map and the turbo will choke out meaning turbo speeds will increase greatly and efficiency goes down quickly. Garret states this line is at 58% or below efficiency. Air stops flowing correctly, heats generated and damage to turbo can occur. Lots of heat = bad.
Too far to the left of the map is the surge line. From garrett: Operation to the left of this line represents a region of flow instability. This region is characterized by mild flutter to wildly fluctuating boost and “barking” from the compressor. Again bad, damage to turbo can occur. Too much air, no where to go.
So looking at the GT2052R, it's going to be choking out big time at 22psi. At lower boost numbers it will be OK, but will run out of air to push rather quickly.