Estimating engine power

This calculator will help you estimate the potential of an engine. Roll your pointer to the left of the table to see typical values. There are tooltips over each input to tell you which values are affected by this input.

For the theory behind the calculator see the engine page.

Atmospheric air conditions:

pressure* :	99 kPa	temperature* :	25 °C	density :	1.1575 kg/m³
*For SAE J1349 Certified Power use pressure = 99 kPa and temperature = 25°C.

typical piston engine

typical Wankel engine

other reciprocating/rotary engine

other

strokes per cycle : 4

revolution per stroke : 0.5 rev

revolution per cycle : 2 rev

I want to build the thermodynamic cycle

Thermodynamic cycle

Legend

PR: Pressure Ratio − η_∞c: Polytropic efficiency − η_int: Intercooler effectiveness − T_c: Coolant temperature − P: Output air pressure − T: Output air temperature − ρ: Output air density − W: Work done (kJ/kg) − CR: Compression Ratio − ER: Expansion Ratio − n: Polytropic index − q_f: Fuel heating value (MJ/kg) − AFR: Stoichiometric Air-Fuel Ratio − r_v: Constant-volume combustion portion − n_o: Combustion overall efficiency − N₂O: Quantity of nitrous oxyde added (lbm/min)

Units for pressure, temperature and density are the same as for the atmospheric air conditions above.

Show compressors & intercoolers                                  Show turbines

dummy value

Intake	Engine	Exhaust
LP compressor <none> turbo centrifugal roots screw vane axial comprex <custom> LP intercooler <none> air-to-air liquid-to-air <custom> PR  η∞c  % ηint  % Tc P T ρ W MP compressor <none> turbo centrifugal roots screw vane axial comprex <custom> MP intercooler <none> air-to-air liquid-to-air <custom> PR  η∞c  % ηint  % Tc P T ρ W HP compressor <none> turbo centrifugal roots screw vane axial comprex <custom> HP intercooler <none> air-to-air liquid-to-air <custom> PR  η∞c  % ηint  % Tc P T ρ W	compression cast iron head aluminum head water injection <custom> CR  :1 n  P T ρ W combustion regular gas premium gas super gas aviation gas diesel kerosene methanol nitromethane ethanol propane LNG hydrogen methane butane ether acetone acetylene <custom> worst ret. ign. poor typical good best <custom> 0 hp 25 hp 50 hp 100 hp 200 hp 300 hp 400 hp <custom> qf AFR  :1 rv % ηo % N2O P T ρ W expansion ER = CR <custom> ER  :1 n  P T ρ W	HP turbine <none> LP compressor MD compressor HP compressor crankshaft low eff. typical hi eff. <custom> PR  η∞t  % P T ρ W MD turbine <none> LP compressor MD compressor HP compressor crankshaft low eff. typical hi eff. <custom> PR  η∞t  % P T ρ W LP turbine <none> LP compressor MD compressor HP compressor crankshaft low eff. typical hi eff. <custom> PR  η∞t  % P T ρ W

engine type BMEPd* @ max power 2-stroke − diesel 8.3 bar 2-stroke − no tuning 8.8 bar 4-stroke − diesel 9.4 bar 4-stroke − Wankel** (turbocharged) 9.5 bar 2-stroke − tuned 9.6 bar 4-stroke − forced induction (crankshaft driven) 9.6 bar 4-stroke − Wankel** 9.9 bar 4-stroke − low CR 10.0 bar 4-stroke − forced induction (exhaust gas driven) 10.5 bar 4-stroke − typical 11.0 bar 4-stroke − high performance 12.0 bar Dragster - Top Fuel 45.0 bar *Note: Based on SAE J1349 air conditions. **Note: Modern Wankel engines tend to have values closer to typical piston 4-stroke engines.

Air factor (λ) : 0.85 AFR (stoich) : 14.7 BSFC : 0.50 lbm/hp/h

BMEPd : 11.0 bar

intake & exhaust tuning VEun-boost @ max power None (2-stroke & Wankel) 55% None (4-stroke) 75% Mild intake tuning (4-stroke) 80% Mild intake & exhaust tuning (4-stroke) 90% Tuned 95% Fully tuned 100% Best 110%	VEun-boost : 90 %   boost gauge pressure : 0 psi   pressure ratio : 1	VEboost :  90 %   BMEP :  9.9 bar Torque :  100 lb.ft
engine type mean piston speed @ max power small industrial engine 7 m/s marine & generator 8.5 m/s train & truck 11 m/s automobile (low speed) 14 m/s automobile (typical) 16 m/s automobile (hi-performance) 18 m/s racing (endurance) 22 m/s racing (short race) 25 m/s drag racing 30 m/s	mean piston speed :  17 m/s  mean rotor tip speed :  24.00 m/s	RPM :  2000 rpm

number of cylinders : 8 bore : 4 in   bore/stroke ratio : 1.333 stroke : 3 in   total bore area : 100 in²   number of rotors - Nr : 2 radius - R : 7 in   R/e : 7 width - W : 5 in   W/R : 0.75 eccentricity - e : 1 in   NrWe : 100 in²

displacement (per rev) : 301.5 ci   displacement (per cycle) : 301.592895 ci

Volumetric flow rate: 100 cfm

c o m p u t e d  b y :

Power: 100 hp