XSI Twin Turbo

[PugLee]

Nothing physically happening to the car at the moment, but i have been working on mapping the compressor charts.

So here is some mathematics for your enjoyment!

This is for the T28

Its all in american units because 124 cubic inches is easier to work with thatn 2045cc

Cubic Inch Displacement (CID) = 124.8

Volumetric Flow Rate (VFR) = (124.8*7000)/3456 = 252.8 Cubic Feet/Min (CFM)

Ive assumed a Volumetric Efficiency of 85% so...

VE = 252.8*0.85 = 214.9 CFM

Mass Flow Rate (MFR) = (2.703*14.7*214.9)/(70+460) = 16.11 lbs/min (2.703 and 460 are constants, 70 is ambient air temp in fahrenheit)


Pressure Ratio (Pr) = (16+14.7)/(14.7-2) = 2.42 (The -2 is to account for pressure drop, -1 each from air filter and intercooler)


Temperature of air coming out of turbo (COMPt) = (((70+460)*2.42^0.283)-460-70)/0.75 = 200.8+70 = 270.8 Fahrenheit (f) (0.283 is a constant, the 0.75 is an assumed turbo efficiency of 75%)


Temperature of air coming out of intercooler (INTt) = (270-70)*0.75 = 150 f (Again, the 0.75 is an assumed intercooler efficiency of 75%)


Density Ratio (Dr) = ((70+460)/(150+460)) = 0.87*2.42 = 2.1

Now if I take my Dr and multiply it by my MFR = 2.1*16.11 = 34 lbs/min

Doing it all again @3500RPM gives me 17 lbs/min


So now i can map it on the compressor chart, looks a little something like this...