Ionization current measured at the spark plug during combustion in spark ignition engines has often been proposed to determine the crank-angle at combustion pressure peak, namely the peak pressure angle, for the purpose of regulating spark timing to attain maximum brake torque (MBT). The proposal is based on the assumption that agreement exists between peak pressure angle and the angular position of the ionization current second peak, although no one has ever proved it by an appropriate statistical analysis. The aim of this work, for the first time and by rigorous statistical methods, is to prove the agreement between Peak Pressure Angle and Ionization Current Second Peak Angle (ICSPA), without which a MBT control via ICSPA would be ineffective. Our experimental database consisted of about 9000 pairs of Peak Pressure Angle and Ionization Current Second Peak Angle values corresponding to 90 different operating conditions of a spark ignition engine. A two-sample comparison was first carried out between mean values of Peak Pressure Angle and Ionization Current Second Peak Angle, which showed a statistically significant difference between them. Then Bland-Altman analysis (Lancet, 1986), widely known and used for checking agreement between two different measurement methods, was conducted. It demonstrated that under almost all the experimental operating conditions, there was no agreement between the Ionization Current Second Peak Angle and the Peak Pressure Angle.

在火花点火发动机燃烧期间在火花塞处测量的电离电流经常被提议用于确定燃烧压力峰值处的曲轴转角，即峰值压力角，以便调节点火正时以获得最大制动扭矩（MBT）。该提议基于峰值压力角和电离电流第二个峰值的角位置之间存在一致的假设，尽管没有人通过适当的统计分析证明这一点。这项工作的目的是首次通过严格的统计方法证明峰值压力角和电离电流第二峰值角 (ICSPA) 之间的一致性，否则通过 ICSPA 的 MBT 控制将是无效的。我们的实验数据库包含大约 9000 对峰值压力角和电离电流第二峰值角值，对应于火花点火发动机的 90 种不同操作条件。首先对峰值压力角和电离电流第二峰值角的平均值进行了双样品比较，结果表明它们之间存在统计学上的显着差异。然后进行了广为人知并用于检查两种不同测量方法之间一致性的 Bland-Altman 分析（Lancet，1986）。它表明在几乎所有的实验操作条件下，电离电流第二峰值角和峰值压力角之间没有一致性。首先对峰值压力角和电离电流第二峰值角的平均值进行了双样品比较，结果表明它们之间存在统计学上的显着差异。然后进行了广为人知并用于检查两种不同测量方法之间一致性的 Bland-Altman 分析（Lancet，1986）。它表明在几乎所有的实验操作条件下，电离电流第二峰值角和峰值压力角之间没有一致性。首先对峰值压力角和电离电流第二峰值角的平均值进行了双样品比较，结果表明它们之间存在统计学上的显着差异。然后进行了广为人知并用于检查两种不同测量方法之间一致性的 Bland-Altman 分析（Lancet，1986）。它表明，在几乎所有的实验操作条件下，电离电流第二峰值角和峰值压力角之间没有一致性。