To study the economic advantages of hydrogen internal combustion engine,an experimental study was carried out using a 2.0Lport fuel-injected(PFI)hydrogen internal combustion engine.Influences of fuel-air equivalence ratioΦ,speed,and ignition advance angle on heat efficiency were determined.Test results showed that indicated thermal efficiency(ITE)firstly increased with fuel-air equivalence ratio,achieved the maximum value of 40.4%(Φ=0.3),and then decreased whenΦ was more than 0.3.ITE increased as speed rises.Mechanical efficiency increased as fuel-air equivalence ratio increased,whereas mechanical efficiency decreased as speed increased,with maximum mechanical efficiency reaching 90%.Brake thermal efficiency(BTE)was influenced by ITE and mechanical efficiency,at the maximum value of 35%(Φ=0.5,2 000r/min).The optimal ignition advance angle of each condition resulting in the maximum BTE was also studied.With increasing fuel-air equivalence ratio,the optimal ignition angle became closer to the top dead center(TDC).The test results and the conclusions exhibited a guiding role on hydrogen internal combustion engine optimization. To study the economic advantages of hydrogen internal combustion engine, an experimental study was carried out using a 2.0Lport fuel-injected (PFI) hydrogen internal combustion engine. Influences of fuel-air equivalence ratioΦ, speed, and ignition advance angle on heat efficiency were determined.Test results showed that that indicated thermal efficiency (ITE) prior increased with fuel-air equivalence ratio, achieved the maximum value of 40.4% (Φ = 0.3), and then decreased decreased whenΦ was more than 0.3.ITE increased as speed rises. efficiency increased as fuel-air equivalence ratio increased, increased the mechanical efficiency decreased as speed increased, with maximum mechanical efficiency reaching 90% .Brake thermal efficiency (BTE) was influenced by ITE and mechanical efficiency, at the maximum value of 35% (Φ = 0.5,2 000 r / min). The optimal ignition advance angle of each condition resulting in the maximum BTE was also studied. With increasing fuel-air equivalence ratio, the optimal ignition angle became clos the test results and the conclusions exhibited a a guiding role on hydrogen internal combustion engine optimization.