i need some help figuring out how to read compressor maps.

I found this site:
http://www.lovehorsepower.com/MR2_Do..._flow_maps.htm

so i first calculated the engine air flow rate (CFM) for my semi-built z6. (zex cam and valve springs hence the 7500 rev limit)

CFM = (L x RPM x VE x PR) / 5660

Where L = engine capacity in liters
RPM = maximum engine speed (we'll adjust this later)
VE = engine volumetric efficiency.* From A. Graham Bell's book Forced Induction Performance Tuning some good values for VE are:
Stock 2-valve = 85%
Stock 4-valve = 90%
Street modified = 93%
Competition = 105%
Pr = pressure ratio = To calculate the pressure ratio you need to know what boost pressure you want to run and then plug that into the following formula:
Pr = 14.7 + Boost
**** 14.7
14.7 + 15 = 29.7/14.7 = 2.02

CFM = 1.6 x 7500 x 90 x 2.02 / 5660
CFM = 1.6 x 4000 x 90 x 2.02 / 5660

To convert this value to lb/min take CFM and divide by 14.27.

CFM = 385.44 @ 7500 rpm
lb.min = 27.01 @ 7500 rpm

CFM = 205.57 @ 4000 rpm
lb.min = 14.41 @ 4000 rpm

so now that I have my pressure ratio and air flow I can plot points on the compressor maths (assuming my calculations are correct) what should I be looking for? what exactly do the "islands" mean?

I currently have the small greddy turbo which is fun but i would like to be just shy of 300hp. How do you factor in HP into these calculations?

 

which greddy turbo?

 

the greddy tdo4-15g (92-95 SOHC civic kit) I think that is the map i posted above?

 

The Greddy 18G still uses the same flange pattern for the car internally wastegated and will fit that manifold.

 

yeah, i have read about how you can make that work with a flange spacer. I'm not opposed to switching manifolds and go to an external modified. I was trying to be more self suffient and knowledgeable about reading maps.

i think the gt28 also bolts to my manifold.

but other turbo options could be the t3 57 trim with around the .48 ar? There are many variations, hence the map question.

thanks for the help!