compressor maps?

[egpower904]

ive seen compressor maps posted all over here and i would really like for someone to explain to me how to read it. im just guessing that the shaded area is its efficiency?? even if i figure out how to read it on my own, what do the different things mean in terms of how a car will perform with "x" turbo. thanks. heres one i saw.

[gastroker]

The further up and to the right you go the more power you make. But the hotter your intake temps get and the higher your shaft speed is spinning. Add a zero to the numbers along the bottom and that is a rough idea of where the horsepower will be. So, this turbo is most efficient in the 200 hp range but could make around 350 really pushing the boost up. But you better have a really good intercooler.

[egpower904]

thanks man that makes sense. i figured i had to be something about efficiency but wasnt sure. and i just picked this turbo at random for the threads sake. i have a garrett .57 trim t3t4 now im gonna go look it up keeping this in mind. thanks dude rep

[gastroker]

here's a really great explanation on reading a compressor map. I'ts a little complicated, but the dummy version is:
Pressure ratio equals boost + 14.7 and then divided by 14.7 at sea level.
The example they use is: your boost gauge reads 12 psi.
So 12 + 14.7 (atmospheric )= 26.7. This is your absolute pressure.
Now divide 26.7 by 14.7 = 1.82.
This is your pressure ratio along the left side of the compressor map.


Make sense?

http://www.turbobygarrett.com/turbob...o_tech103.html

[crashtke]

The little islands on the map are also how efficient the turbo is at those levels/airflows. So you want your car to stay in the efficeincy range of the turbo. To the right of the map is generally where the turbo runs out and is no longer able to flow efficiently. To the left of the map, the turbo will surge and not perform.

[egpower904]

thanks both of you guys reps. i get it now will come in handy when selecting my next bigger turbo ....