An automobile engine operates at a fuel air ratio of 0.05,

An automobile engine operates at a fuel air ratio of 0.05, volumetric efficiency of 90% and indicated thermal efficiency of 30%. Given that the calorific value of the fuel is 45 MJ/kg and the density of air at intake in 1 kg/m³, the indicated mean effective pressure for the engine is

Given,	Fuel	= 0.05
	Air

η_volumetric = 90%
η_thermal = 30%
Calorific value = 45 MJ/kg

	m_f	= 0.05
	m_a

ρ_air = 1 kg/m³
Volumetric efficiency,

η_v=		actual volume	=	v_ac
		swept volume		v_s

∴ V_ac = 0.9 V_s
m_a = ρ_airV_ac
= 1 × 0.9 × V_s
= 0.9 V_s
m_f = 0.05 × 0.9 V_s = .045 V_s

η_thermal =	p_mep × LAN
	m_f × 45 × 10⁴⁶

0.3 =	p_mep × V_s
	0.45V_s × 45 × 10⁶

... since LAN = V_s
p_mep =0.3 × 0.045 × 45 × 10⁶ = 6.075 × 10⁵N/m²
= 6.075 bar