Max Boost Before a Charge-Air Temperature Limit
The gauge boost at which the compressor-outlet charge-air temperature reaches a limit.
Example
You enter
- Charge-air temperature limit (°F) 250
- Compressor inlet air temp (°F) 80
- Compressor isentropic efficiency (%) 70
- Ambient pressure (psia, 14.7 at sea level) 14.7
You get
- Max boost (gauge) 14.8 psi
- Pressure ratio at the limit 2.01
Checked against published worked examples from: GFB Performance.
Details, formula, and sources
Scopeboost = ambient x ([1 + eff x (T_out/T_in - 1)]^(1/0.2857) - 1). An 80 F inlet, 70% compressor, 250 F limit tops out near 15 psi; a more efficient compressor or a cooler inlet buys more. Compressor-outlet temp (ignores intercooling). A planning estimate; the compressor map and engine build govern.
Formula or tablePR = [1 + (efficiency/100) x (T_out/T_in - 1)]^(1/0.2857); max_boost = ambient_psia x (PR - 1); temperatures absolute (Rankine). The charge-air-temperature model solved for the boost.
Source and editionTurbocharger charge-air-temperature model (compressor-map sizing; ideal-gas adiabatic compression with gamma = 1.4) solved for the boost, first-principles, by name; the compressor map and the engine build govern.
Free accessThe pressure-ratio and adiabatic-temperature relations are first-principles thermodynamics; the temperatures, efficiency, and ambient come from the application and the compressor map.
What governsEstimate. AHJ and licensed professional govern.
API field namesmax_charge_temp_f, inlet_temp_f, compressor_eff_pct, ambient_psia, max_boost_psi, pressure_ratio
- Gauge boost PR uses absolute pressures; max_boost = ambient x (PR - 1) recovers the gauge boostcompressor-map sizing
- Heat of compression solves T_out = T_in x [1 + (PR^0.2857 - 1)/efficiency] for PRadiabatic compression (gamma = 1.4)
- No intercooler the limit is the compressor-outlet temperature, not the post-intercooler manifold temperaturescope of this tile