One of the most common methods of trimming the fuel delivery on each cylinder is to use individual cylinder EGT (exhaust gas temperature) sensors. These sensors are K-type thermocouples that are placed in the exhaust header to directly measure the exhaust gas temperature. The theory is that as we richen the mixture, the combustion temperature and hence EGT is cooled by the additional fuel. Now we can trim each cylinder’s fuel delivery in an effort to achieve consistent EGT values. For the most part, EGT sensors are a pretty good way of monitoring engine operation, however for ultimate accuracy they do have some limitations. For example, the EGT reading will depend on how far from the exhaust valve the sensor is located, how far the tip of the sensor extends into the exhaust runner, and the actual type of sensor (exposed tip vs encased tip). Then, aspects such as ignition timing and cylinder head and block temperature can also play a part in the readings. Lastly, EGT sensors also respond quite slowly – Even the best have a response time of 150 ms or worse. If you want a true indication of how each cylinder is operating, individual cylinder lambda sensors are the best option.
If you want to learn more about EFI tuning, check High Performance Academy’s EFI Fundamentals course.