I've read the turbo basics link posted by WDRacing and still want to clear up some things that I don't understand about the turbo.
http://www.automotivearticles....pid=1
First trim and and A/R. How does trim and A/R affect efficiency? Tell me both the negatives and positives please. For instance by increasing A/R you make " " better but hurt " ". What exactly is A/R and how is it calculated? Trim I believe is just turbine or compressor wheel size compared to the housing that its in. Correct me if I'm wrong. Also how is trim calculated? And the negatives and positives of increasing or decreasing trim size.
Lastly this is gonna seem stupid to you turbo guys, but someone chart the flow of air to me from the turbo. Turbo compresses air > intercooler > intake piping or intake manifold? > engine? --- I don't understand where a regular intake system comes into play if its being force fed air from the turbo?
Help me understand turbo's better.
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C-Kwik
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Trim affects efficiency similarly to the way size does. Bigger wheels tend to have better efficiency at higher pressure ratios and flowrates since they thrash the air around less. Trim is typically changed within a turbo grouping(T3 or T4B or T4E, etc) by changing the minor diameter. Typically the major diameter stays the same, unless you go to an overall larger or smaller turbo. Not sure of the actual math involved with calculating trim. As far as the pros and cons, it depends. What you have to do is map out the boost/airflow curve on compressor maps to determine the best match for your motor and boost level.
A/R doesn't affect efficiency. It inversely affects response and flow. A/R tends to be more critical to the turbine section, but can have a small affect if you change the A/R in the compressoer section. I'll refer to the turbine A/R as it is a bit easier to understand. When air is entering the turbo, it has to pass through a "nozzle" before it hits the turbine wheel. The size of this nozzle is the area, or the "A" in A/R. The smaller the nozzle, the faster the velocity of the air going through it. But smaller nozzles are more restrictive. And the opposite is true of larger nozzles. Faster air will speed up a turbo quicker. The "R" refers to radius. Basically the distance from the center of the nozzle to the center of the turbine wheel. Typically, for a given turbo size, the A/R is changed only by changing the size of A. Radius is in there though since the location of the nozzle in relation to the center of the turbine wheel changes how much leverage the air has on the turbine wheel. Air on the outer edge of a turbine wheel will spool up a turbo faster than it would if the air was aimed fartehr in.
As far as the path of air, your flow chart is the way air would go through a turbo system. You don't use a regular intake(if you are referring to say an Injen or Hotshot intake, etc). It's possible you could incorporate it, but you'ld likely have to make some modifications to it or the way some lines run to it.
A/R doesn't affect efficiency. It inversely affects response and flow. A/R tends to be more critical to the turbine section, but can have a small affect if you change the A/R in the compressoer section. I'll refer to the turbine A/R as it is a bit easier to understand. When air is entering the turbo, it has to pass through a "nozzle" before it hits the turbine wheel. The size of this nozzle is the area, or the "A" in A/R. The smaller the nozzle, the faster the velocity of the air going through it. But smaller nozzles are more restrictive. And the opposite is true of larger nozzles. Faster air will speed up a turbo quicker. The "R" refers to radius. Basically the distance from the center of the nozzle to the center of the turbine wheel. Typically, for a given turbo size, the A/R is changed only by changing the size of A. Radius is in there though since the location of the nozzle in relation to the center of the turbine wheel changes how much leverage the air has on the turbine wheel. Air on the outer edge of a turbine wheel will spool up a turbo faster than it would if the air was aimed fartehr in.
As far as the path of air, your flow chart is the way air would go through a turbo system. You don't use a regular intake(if you are referring to say an Injen or Hotshot intake, etc). It's possible you could incorporate it, but you'ld likely have to make some modifications to it or the way some lines run to it.
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Emperor240
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=) It's all starting to make sense now.
For further clarification for me - Lets say for instance we have the hybrid turbo the T3/T04E one at 50, 57, and 60 trim. Now I know C-Kwik said to look a compressor map for best efficiency. But typically - is smaller trim for lower boost levels and larger trim for larger boost levels? Does changing trim affect responsiveness? I'm just looking for a general idea on how trim affects turbo. Any other info that you may think would be helpful, please add. C-Kwik's response just about nailed it down on the head for me.
Ok, so now I know the turbo flow. But does the engine draw air thru the intercooler w/out boost if say you're idling or just starting the engine? And if you don't have an intercooler, where would the engine draw air from in previous example?
For further clarification for me - Lets say for instance we have the hybrid turbo the T3/T04E one at 50, 57, and 60 trim. Now I know C-Kwik said to look a compressor map for best efficiency. But typically - is smaller trim for lower boost levels and larger trim for larger boost levels? Does changing trim affect responsiveness? I'm just looking for a general idea on how trim affects turbo. Any other info that you may think would be helpful, please add. C-Kwik's response just about nailed it down on the head for me.
Ok, so now I know the turbo flow. But does the engine draw air thru the intercooler w/out boost if say you're idling or just starting the engine? And if you don't have an intercooler, where would the engine draw air from in previous example?
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C-Kwik
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Larger trims have a higher max flow capability, so for the most part, yes, higher trims tend to be designed with higher flow in mind, but in actual application, it doesn't always work out that way. Since efficiency in part determines how much actual air your engine takes in, a larger trim can actually flow less than a smaller trim for a given engine size, speed and boost level.
When you are off boost, the air still goes through the intercooler. The air actually takes the same path when you are on and off boost. The only exception would be vent air from the blow-off valve, which could be rerouted before the turbo or vented into the atmosphere depending on the set-up.
When you are off boost, the air still goes through the intercooler. The air actually takes the same path when you are on and off boost. The only exception would be vent air from the blow-off valve, which could be rerouted before the turbo or vented into the atmosphere depending on the set-up.
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mynameisjonas
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great basic article on how turbos work, with pictures and other links
http://auto.howstuffworks.com/turbo.htm
http://auto.howstuffworks.com/turbo.htm