boost presser and power gain

Greg Hermann bearbvd at sni.net
Mon Aug 31 23:26:48 GMT 1998


>Hi  Guys!
>
>What interdependence is between boost presser  and power gain?
>If not turbo engine is 100 hp, what power growth will obtain by 2 bar
>(absolute) boost? And how march reduction of compression ratio will
>needed?

Boost pressure is not the significant thing. DENSITY is what you need to
figure. Mass/hour of air through engine relates directly to HP (or KW)
output. Density is a function of both manifold absolute pressure and
manifold absolute temperature, based on PV=nRT or PV= rho k T (gas law) (R,
k, and  n  and V remain constant for a given gas in a given engine at a
given speed, so formula simplifies to PV/T=k (rho) (where rho =density) for
a given engine situation. Sorry this is not too clear, e-mail doesn't do
subscripts and Greek very well. In British units, Rho=.0762 lbs./cu. ft. at
standard temperature and pressure, which are 14.69 psia and 69 degrees F
(same as 528.9 degrees Kelvin (absolute). You should be able to do simple
ratio calculations based on these numbers and you proposed (or actual)
manifold pressure and temperature to arrive at you manifold density. Mass
flow of air through engine is equal to displacement times .5 (for a four
stroke) times engine speed times manifold density times volumetric
efficiency. Depending greatly on engine characteristics, particularly
compression ratio, Each 1 pound per hour of air flow through an engine will
give in the range of 7 to 8.5 HP of output from a turbocharged engine.

Regards, Greg
>
>If anyone has these formulas,  please let me know!
>
>Sergey Stopov
>
>EmailToefi335 at hotmail.com
>
>
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