tech turbo quiestion
raven_240
05-10-2004, 05:18 PM
OK. Now I have a good idea on how to fined the right compressor for my engine by maping my engine's air requierments at any given boost on a compressor map. You can do this using one of two equations
First the esiast one to use is CFM = (L x RPM x VE x Pr)/5660
where L=liters of your engine, VE= your engins eficiancy usaly between 85-95% and Pr= pressure ration found by the equation Pr=(14.7+(boost you are running))/14.7.
this worked for maping my t25 turbo out on my 2.0 liter sr20det pritty acuratly at 10psi.
the other one you can use is EVF=(engineCID)/1728 * (rpm/2)
then take the evf, witch is in CMF, and convert it to lbs/min using this formula
N=(P*EVF*29)/(10.3*T)
Where N is the airflow in lb/min, P is the absolute pressure in psi, and T is the absolute ambient temperature in Rankin.
Finally, multiply N by the volumetric efficiency of your engine (VE). This compensates for the fact that upon every cycle of the engine, not all of the old air/fuel mix in the cylinders is forced out the exhaust. Thus there is a difference .
Firs question is wich method is more acurate, second anyone know how to match the turbine to your engine?
First the esiast one to use is CFM = (L x RPM x VE x Pr)/5660
where L=liters of your engine, VE= your engins eficiancy usaly between 85-95% and Pr= pressure ration found by the equation Pr=(14.7+(boost you are running))/14.7.
this worked for maping my t25 turbo out on my 2.0 liter sr20det pritty acuratly at 10psi.
the other one you can use is EVF=(engineCID)/1728 * (rpm/2)
then take the evf, witch is in CMF, and convert it to lbs/min using this formula
N=(P*EVF*29)/(10.3*T)
Where N is the airflow in lb/min, P is the absolute pressure in psi, and T is the absolute ambient temperature in Rankin.
Finally, multiply N by the volumetric efficiency of your engine (VE). This compensates for the fact that upon every cycle of the engine, not all of the old air/fuel mix in the cylinders is forced out the exhaust. Thus there is a difference .
Firs question is wich method is more acurate, second anyone know how to match the turbine to your engine?
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