Let us discuss turbo compressor efficiency

[RC K9]

So I am trying to learn how to read compressor maps. Now, I know that comp maps need to be taken with a grain of salt as they do not take into account engine size, VE, intercooler efficiency, etc. But for the sake of reading a map and getting a ballpark idea, I need to know if I am doing this right:

 

Here we have the comp map for an MHI 14b turbo (stock turbo for 5spd 1st gen dsms)

 

http://i49.photobucket.com/albums/f256/smokey18328/14bcfm.jpg

 

Now, my understanding is that the center of the first middle island is where the compressor is most efficient. So in this turbos case, its most efficient at about 10psi (PR of about 1.7)

 

On this turbo, (Garrett 3582), it is most efficient at 18psi (PR 2.25, about 40lbs/min)

 

http://www.himni-racing.com/images/gt3582rcomp_e.jpg

 

Now if I break out of these boost settings/pressure ratios, and lets say on the 14b run 15psi (about 2.0PR), and/or run about 30psi (PR od 3.0 at 52lbs/min), these turbos should still be relatively efficient correct?

 

I just want to know if I am reading these right.

Edited January 6, 2013 by RC K9

[Alfa Turbo]

The islands have an efficiency percentage associated with them and they are not the same turbo to turbo. Just because 2 different turbos are in the middle island does not mean they are at the same efficiency. Also, consider for a moment the middle islands were the same efficiency percentage. The 35 will be moving much more volume (of air) than the 14b so it is not an apples to apples comparison.

 

What is it you are trying to do?

[RC K9]

The islands have an efficiency percentage associated with them and they are not the same turbo to turbo. Just because 2 different turbos are in the middle island does not mean they are at the same efficiency. Also, consider for a moment the middle islands were the same efficiency percentage. The 35 will be moving much more volume (of air) than the 14b so it is not an apples to apples comparison.

 

What is it you are trying to do?

 

I am not trying to compare the turbos. I am just using those two turbos compressor maps of examples in my question of how to properly interpret them.

 

As I believe I stated before, the 14b appears to be most efficient at PR 1.7 (10psi) and 250cfm, but could still be fairly efficient at 15psi and 27lbs/min.

 

My interpretation of the 3582 map is that is it most efficient at a PR of about 2.5 and 45lbs/min, but could still be relatively efficient at a PR of 3-3.5 (29-36psi) and flow 55-60lbs/min.

 

I just want to know if I am looking at these maps right.

 

And for as to what I am trying to do, I am just thinking about if I were to "hypothetically" run a compound setup, at what boost levels each turbo would be in its efficiency range. I would think 15psi on a 14b and 30psi on the 3582 would do nicely for both.