There are many factors that affect how fast PIDs are refreshed, including the connected vehicle, the adapter, and the number of PIDs you are monitoring and logging. This page provides a number of suggestions on how to monitor and improve the PID refresh rate.
You can monitor the Total Refresh Rate on the Settings > About > Information page when connected to the vehicle or by selecting the System > PID refresh rate PID. The Total Refresh Rate is displayed in PIDs/second and represents the total number of PIDs read from the vehicle each second. The refresh rate for each individual PID, referred to as the Individual Refresh Rate, depends on the Total Refresh Rate and the number of PIDs that you are monitoring and logging. For example, if the Total Refresh Rate is 40 PIDs/second and you are monitoring/logging 10 PIDs, then the Individual Refresh Rate will be approximately 4 refreshes per second. Similarly, if you are only monitoring/logging 4 PIDs, then the Individual Refresh Rate will be approximately 10 refreshes per second.
In general, the Total Refresh Rate will stay fairly constant regardless of the number of PIDs that you are monitoring. However, this is not always the case because different PIDs return different amounts of data from the vehicle. For example, a PID that returns 12 bytes of data will take slightly longer to read than a PID that only returns 2 bytes of data. In addition, if you are using an enhanced diagnostic add-on and displaying PIDs from different modules, the Total Refresh Rate will be reduced due to the time required to switch between each of the different modules. There are a few settings that can improve the Total Refresh Rate, and each setting is explained below.
Fast Polling
Fast Polling can be enabled on the Settings > Preferences > Communications page. This setting reduces the amount of time that the adapter waits for a response from the vehicle. When enabled, this setting can greatly improve the total refresh rate. However, there are some adapters that do not support this setting, so you might have to disable it if you experience any issues reading PIDs with it enabled.
Combine SAE PID Requests
Combine SAE PID Requests can be enabled on the Settings > Preferences > Communications page. This setting can drastically improve the total refresh rate by requesting multiple SAE PIDs from the vehicle at the same time. There might be some vehicles that do not support this setting, so you might have to disable it if you experience any issues reading PIDs with it enabled. This setting only applies to vehicles that use the CAN protocol.
Dwell Time
Dwell Time can be configured on the Settings > Preferences > Communications page. The dwell time is the time that the app waits between each subsequent data request from the vehicle. The default value for this setting is 0 (do not wait).
Increasing the Total Refresh Rate will improve the Individual Refresh Rate. The suggestions listed below are additional ways that you can improve the refresh rate for each individual PID.
Reduce The Number Of PIDs Being Logged
Logging is configured on the Settings > Preferences > Logging page. PIDs that are being logged to file are read from the vehicle regardless of the page you are viewing. If you don't need to log data to file, then you can disable logging. If you do need to log data to file, then review the PIDs that you configured in the logging settings and only select the PIDs that you need to log.
Reduce The Number Of PIDs Being Monitored
In addition to any PIDs that you configured for logging, the PIDs being displayed on the active page are constantly being read from the vehicle. If you are displaying a large number of PIDs, then the individual refresh rate for each PID will be reduced. Review the PIDs that you have configured for display and remove any that you don't need.
Disable Background Calculations If Not Needed
PIDs that are required for fuel, trip, and EV/hybrid calculations are read from the vehicle regardless of the page you are viewing. If you don't care about the trip calculations, such as distance, fuel, EV/hybrid energy etc., and you don't care to view or log the fuel rate, fuel economy, or power and torque PIDs, then you can disable these calculations by enabling the Disable Background Calculations preference on the general preferences page. We don't recommend disabling background calculations unless you need to view PIDs that are unrelated to these calculations at the fastest rate possible.
The refresh rates are ultimately limited by the adapter you are using and the connected vehicle. This section provides some information on those limitations.
Adapter Limitations
Some adapters perform better than others and can read data and communicate with the app and vehicle must faster. Some of the cheap ELM327 adapters can drastically reduce the refresh rates because they return errant data. When an error is detected in a response from the adapter, the request has to be re-tried which will slow down the refresh rate.
Vehicle Limitations
One of the biggest factors that affect the refresh rate is the protocol used by the vehicle. Most newer vehicles that were sold after 2006 use the CAN protocol, which is currently the fastest protocol and results in the best refresh rate. Older vehicles use either J1850, ISO-9142-2, or ISO-14230-4 (KWP). The ISO protocols are by far the slowest protocols and in some cases, can only transmit about four PIDs per second. Unfortunately, if your vehicle uses one of these slower protocols, there is not much that you can do to improve the refresh rate because the rate is limited at the vehicle hardware layer. You can see which protocol your vehicle uses on the Settings > About > Information page when connected.