Need help on Turbocharging a 318
First you need to set a horsepower target & stay with it through the design process. You first said 400 horsepower, then 450 horsepower.
Second, you need to learn to read a compressor map & begin thinking in mass air flow, generally expressed in pounds of air per minute on compressor maps.
For your initial goal of 400 horsepower from a 318, the basic calculation shows 40 lbs/min. airflow, and a little under 7 psi of boost with a discharge temp of 160f. For 450 horsepower, you need 45 pounds per minute & 9.5 psi of boost.
Next you need to calculate the pressure ratio. That is atmospheric pressure plus boot pressure, then divided by atmospheric pressure:
14.7 + 7= 21.7 then 21.7/14.7 =1.476 That leaves you with a 1.476 : 1 pressure ratio.
Garrett shows 3 compressor maps for the GT35 series. None of them will support 40 pounds per minute flow at that pressure ratio. The map shows that compressor way out in the choke area. However two of them would be just about right.
For a single turbine on a 318 a T70 would be as much as you would need at that power level. A T72 would be ok, but it would barely be spinning - look at the T72 map:
Now, that same unit @ 650 horsepower pushing 65 lbs / min & a 2.80 pressure ratio (23psi) puts things right in the sweet spot on the map.
Good luck with your project.
B.
First you need to set a horsepower target & stay with it through the design process. You first said 400 horsepower, then 450 horsepower.
Second, you need to learn to read a compressor map & begin thinking in mass air flow, generally expressed in pounds of air per minute on compressor maps.
For your initial goal of 400 horsepower from a 318, the basic calculation shows 40 lbs/min. airflow, and a little under 7 psi of boost with a discharge temp of 160f. For 450 horsepower, you need 45 pounds per minute & 9.5 psi of boost.
Next you need to calculate the pressure ratio. That is atmospheric pressure plus boot pressure, then divided by atmospheric pressure:
14.7 + 7= 21.7 then 21.7/14.7 =1.476 That leaves you with a 1.476 : 1 pressure ratio.
Garrett shows 3 compressor maps for the GT35 series. None of them will support 40 pounds per minute flow at that pressure ratio. The map shows that compressor way out in the choke area. However two of them would be just about right.
For a single turbine on a 318 a T70 would be as much as you would need at that power level. A T72 would be ok, but it would barely be spinning - look at the T72 map:
Now, that same unit @ 650 horsepower pushing 65 lbs / min & a 2.80 pressure ratio (23psi) puts things right in the sweet spot on the map.
Good luck with your project.
B.