Learn to read compressor maps
03-31-2003, 09:48 PM
#1
0.0 BAR
Thread Starter
Join Date: Feb 2003
Posts: 0
Learn to read compressor maps
Will somebody please develop a way to explain how to read compressor maps in english. I have looked into many ways and still don't fully understand what the vertical and horizontal lines mean together. I just get confused on the conversions of ? to cfm and so on. Is it possible in ENGLISH? I think this would help many of our "Which turbo should I use" people. 
04-01-2003, 05:09 AM
#3
3.0 BAR
Join Date: Dec 2002
Posts: 3,830
Re:Learn to read compressor maps
Heres my 2
0am, just got home from the bar, grossly over simplified explanation:
y-axis: pressure ratio. 1=0psi, 1.5=7.35psi, 2.0=14.7psi etc
x-axis: air flow expressed in lbs/min. (the cool thing about lbs/min is that is roughly translates into HP potential. 100hp = 10lbs/min, 250hp = 25lbs/min, etc...)
The large area circles with %'s on them are efficiency islands that express the compressors efficiency at a given plot point.
By looking at dyno sheets from similar engines/setups as your own, you can realistically guess hp potential, and apply it to a turbo's compressor map.
A ZC at 7psi applied to a T3 map:
x-axis airflow lbs/min= 17 (170ish hp)
y-axis pressure ratio= 1.47 (14.7+7)/14.7
Plotting this point puts you on the 70% 'island'. This compressor is 70% effecient at feeding a ZC at 7psi. (roots superchargers blush at these #'s...heheheh)
Turn the boost up to 10-12 and the compressor approaches the 74% island.
Heres a more indepth example that google came up with:
http://shingles.no-ip.com
080/cars/crx/turbo/compmap.asp
'Maximum Boost' has a simple layout on compressor maps as well.
HTH,
Dave
0am, just got home from the bar, grossly over simplified explanation:y-axis: pressure ratio. 1=0psi, 1.5=7.35psi, 2.0=14.7psi etc
x-axis: air flow expressed in lbs/min. (the cool thing about lbs/min is that is roughly translates into HP potential. 100hp = 10lbs/min, 250hp = 25lbs/min, etc...)
The large area circles with %'s on them are efficiency islands that express the compressors efficiency at a given plot point.
By looking at dyno sheets from similar engines/setups as your own, you can realistically guess hp potential, and apply it to a turbo's compressor map.
A ZC at 7psi applied to a T3 map:
x-axis airflow lbs/min= 17 (170ish hp)
y-axis pressure ratio= 1.47 (14.7+7)/14.7
Plotting this point puts you on the 70% 'island'. This compressor is 70% effecient at feeding a ZC at 7psi. (roots superchargers blush at these #'s...heheheh)
Turn the boost up to 10-12 and the compressor approaches the 74% island.
Heres a more indepth example that google came up with:
http://shingles.no-ip.com
080/cars/crx/turbo/compmap.asp'Maximum Boost' has a simple layout on compressor maps as well.
HTH,
Dave
04-02-2003, 02:07 AM
#4
0.0 BAR
Thread Starter
Join Date: Feb 2003
Posts: 0
Re:Learn to read compressor maps
Wow Dave,
Thanks alot. It took me like an hour on that link, but I think I figured out my flow rates and stuff. That's alot of damn math. Thanks
Shortyz- If you could put that into English for others, that would be great. I mean, we shouldn't be here to have people tell us what we should do, we should want to understand it ourselves. Thanks.
P.S. I was just ------' with you in the chat room, I promise.
Thanks alot. It took me like an hour on that link, but I think I figured out my flow rates and stuff. That's alot of damn math. Thanks
Shortyz- If you could put that into English for others, that would be great. I mean, we shouldn't be here to have people tell us what we should do, we should want to understand it ourselves. Thanks.
P.S. I was just ------' with you in the chat room, I promise.
04-02-2003, 02:45 AM
#5
0.0 BAR
Thread Starter
Join Date: Feb 2003
Posts: 0
Re:Learn to read compressor maps
Ok, I went on turbonetics.com and started plotting my points on all the compressor maps. I found that the t3 60 trim was the best. Question- when trying to spot a t3 to buy, how do I know/find out if it is the "60 trim". Maybe you guys know what factory turbo is similar. Please help.
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