This article will attempt to explain the basics of compressor maps and how to read them.<br /> <br /> for this we will be using a GT35R compressor map:<br /> <br /> <img src="http://www.drag240sx.com/datas/users/1-gt35rcompress.gif" align="left">Along the left you will see the Pressure Ratio ranging from 1.0 to 3.4.<br /> <br /> The pressure ratio is a calculation of sea level atmospheric pressure + boost / sea level atmospheric pressure. sea level atmospheric pressure being 14.7psi<br /> <br /> For this example, lets say we want to run our GT35R at 20psi ( 14.7 + 20 / 14.7 = 2.36) which we will round up to 2.4 for simplicity sake.<br /> <br /> Along the bottom of the map you will see airflow, in lbs per min. This is how much air you want your turbo to flow.<br /> <br /> assuming your engine and setup will allow it, your GT35R should be pushing roughly 60lbs per min at 20PSI. putting it at around 65% efficiency. Generally, you want to keep your efficiency above or close to 65%, but it really depends on your application.<br /> <br /> At 65% your at the furthest ring away from the "island". The closer you get to the island, the cooler air the turbocharger will produce. the more airflow, the more power. With just like anything else, there are trade offs.<br /> <br /> If your dropping below 65% at a desired pressure ratio for a desired airflow, its probably time to get a bigger turbo.<br /> <br /> A very rough guess of HP at a given airflow is airflow * 10. While there are much more accurate ways of calculating HP from airflow, this is generally true. a turbo able to flow 40lbs per min, is able to produce 400hp, 60lbs per min 600hp, and so on.<br /> <br /> Hopefully you have found thisbasic article helpful... Happy compressor map reading! Shae Petersen www.drag240sx.com
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