In our first article, Flying Blind: What To Data Log When Tuning A Vehicle, we took a look at some of the basic parameters to look at when tuning a vehicle with EFI Live. This article will expand on this subject matter as we take a look at different operating parameters and tables with the FlashScan V3. So, let’s dive in.
The keys to using logged data successfully to develop an optimal tune file are understanding the operating parameters of various sensors and relating data to actual working conditions.
Typical GM control systems rely on narrowband oxygen sensors (O2) to control fuel flow during idle and part throttle operations. Consequently, data logs should show that the system was in a closed-loop state, which means O2 feedback to the ECM is used to control fuel flow. If the system is in an open loop, the engine hasn’t reached normal operating temperature, the throttle has been depressed far enough to cause a transition out of closed-loop, or a mechanical or electrical problem is preventing the system from activating closed-loop operation. More than one tuner has chased an air/fuel management problem only to eventually learn that the cause was the system not being in a closed-loop.
Closed-loop operation intends to control idle and part throttle air/fuel ratio so that a stoichiometric ratio (+/-14.7:1 with pure gasoline and +/- 14.1 with E10, gasoline containing 10% ethanol) is maintained. Back in the day, before inexpensive wideband O2 sensors were available, many tuners used narrowband voltage readings to adjust wide-open-throttle air/fuel ratios. Those readings may get you close but are not reliable enough to achieve the desired result.
When logging wide-open throttle data, it’s essential to install a wideband O2 sensor and connect its output to a FlashScan or Autocal. That allows the data to be displayed on the same data log as the other ECM data. Wide-open throttle testing should then be done on a racetrack or chassis dyno with the transmission in fourth gear, or the ratio closest to a 1:1 ratio. The longer, slower rate of acceleration in the upper gears will allow more data to be collected during acceleration runs. Be mindful that public streets and highways aren’t the proper places to be doing wide-open throttle tuning.
If long-term fuel trim (LTFT) readings are out of the desired range, the best way to correct fuel flow will differ depending on the complexion of the out-of-range readings. Assuming you’re not dealing with a “whacked” volumetric efficiency (VE) table or a damaged Mass Air sensor (MAF), if the trims are way off across the board (in the same direction), incorrect injector flow rate (B4001) values may be the culprit. In instances with LTFTs being excessively positive at some points and overly negative at others, the most likely suspects are the VE table (B0101) and the Mass Air Flow calibration table (B5001). (Note: in EFILive tuning software, all tables are numbered for easy reference. The numbers in this article refer to LS1 operating systems.)
Several other tables can affect fuel flow. So if the data in the tables mentioned above appears to be correct, or if extreme changes are required to bring LTFT numbers in line, you should look elsewhere:
- B3701- Injector Pulse Width Voltage Adjustment
- B3702- Injection Timing
- B4002- Injector Voltage Correction
- B4003- Minimum Injector Pulse Width
Air/fuel ratio and ignition timing are most commonly the areas of prime interest in a quest for improved performance (and fuel economy). But other “challenges” also exist, so it may be necessary to change the selection of gauges displayed on FlashScan’s virtual dashboard. One of the many advantages of this software is the ease with which existing dashboards can be changed and new ones created.
The system is supplied with many default dashboards with gauges configured for either metric or Imperial data. However, it is possible to alter the “language” displayed in individual gauges. For example, suppose you’re most comfortable with temperatures being displayed in Fahrenheit. In that case, those gauges can be reconfigured to display Imperial data while gauges displaying air flow rates “speak metric” (grams per second).
Notice that the dashboard shown below has been configured as described with temperatures displayed in Fahrenheit and vehicle speed in miles per hour, while air flow and manifold absolute pressure readings are shown in metric units.
Regardless of the flavor of displayed data, it must be consistent with the relevant tables in the tuning program. For example, you don’t want to log temperature in Fahrenheit and correlate data to a table in the tuning program that references Celsius (centigrade back in the day).
In addition to spark and fuel calibrations, the idle quality frequently requires a good bit of tuning work—particularly in vehicles equipped with an automatic transmission. When logging data for use in idle quality tuning, the relevant parameter identifier (PID) is known as Running Air Flow in Gear (RAFIG), which measures the airflow correction performed by the system. If the value in table B4307 is too far off the mark, an excess correction is necessary to provide the airflow required to support the commanded idle speed. The amount of change is shown when RAFIG is displayed on the virtual dashboard.
Running Air Flow in Park/Neutral (RAFPN) is another PID available in FlashScan. Both RAFIG and RAFPN are computed by adding long-term and short-term airflow correction, so those PIDs must also be selected. However, these values don’t have to be displayed when setting up a dashboard for monitoring or data logging idle airflow correction. RAFPN is the relevant PID when an engine is idling and the transmission is either Park or Neutral.
Two other PIDs of interest are RAFACIG and RAFACPN, which display airflow correction when air conditioning is turned on. These PIDs consider the airflow modification activated to compensate for the additional load put on an engine when engine air conditioning is switched on. Tables B4354 through B4370 relate to air and spark compensation for air conditioning load. Although spark settings have no direct impact on airflow, they can indirectly affect the amount of airflow compensation required to maintain commanded idle speed.
The need to address idle quality usually arises after a long duration camshaft is installed, especially if the torque converter isn’t “loose” enough to accommodate the increased idle speed necessitated by the cam. When an automatic transmission is in gear, a relatively high idle speed played against a “tight” converter puts the engine under significantly more load than exists at lower speeds. That additional load increases an engine’s demand for air, and consequently, desired idle air flow must be increased, as specified in table B4307. Even with a high stall converter, or a manual transmission, idle airflow usually has to be increased, if for no other reason than to support an uptick in desired idle speed.
Another special-purpose configuration option the scanning program offers is setting maximum and minimum values for a gauge or chart. Default settings for gauges encompass the entire range of normal operations. However, it may be advantageous to narrow the scope, thereby increasing definition, for specific tasks. For example, when working with issues related to idle, throttle position will remain in the lower end of the range. Minor changes will become much more apparent if the maximum reading is reduced from 100- to 20-percent. Minimum and maximum values are easily changed, so there’s no need to create a unique gauge. However, you may want to do just that and incorporate it into a dashboard that you design for a specific tuning operation.
When monitoring idle airflow, you’ll most likely find a discrepancy between the observed and commanded data due to adjustments initiated by the data in various tables. LS1 PCMs adjust idle airflow to compensate for engine and vehicle conditions changes and can also learn idle airflow correction. These modifiers may cause actual airflow to be higher or lower than the value in table B4307. Consequently, it may require considerable time and effort to bring RAFIG correction to minimum levels. As long as the necessary amount of correction is within limits, proper idle quality can be achieved; the airflow correction (as shown on the RAFIG gauge) deemed acceptable is primarily a matter of personal preference.
During the set up of a custom dashboard, you may well find that the gauges incorporated on “Page A” differs from the charts shown on “Page B” and “Page C.” These pages must be set up separately and allow you to view data in a continual graph format. In addition, you may find that you want different PIDs displayed on each page. Fortunately, it’s possible to accomplish that fairly easily. Extensive dashboard setup and PID selection guidelines are provided with the FlashScan software package.
Correlating Logged Data to Cells in a Table
When tuning, one of the challenges is determining the location of the specific data that must be altered to correct a problem or enhance engine operation. The integration of FlashScan’s scanning and tuning programs simplifies this process by highlighting the cells in a specific table corresponding to the operating conditions selected on a graph of logged data.
For example, if knock retard is evident, click hold and drag the cursor across the appropriate section of the graph. Then switch to the tuning program (both can be open simultaneously) and open table B5913 (High Octane Spark Table). Again, the cells containing spark advance settings for the operating conditions (rpm and engine load) that existed when knock was detected will be highlighted.
As noted previously, the parameters for the PIDs displayed on a chart must be in the same units like those used in the relevant tuning table. Separate metric and Imperial PIDs exist for all parameters expressed in either type of unit, so be sure to select the correct one. Most tables have rows and columns within the tuning program, and unit types may be specified for each.
With these two articles under your belt, you should have a much better understanding of what to data log and what tables to use with EFI Live’s FlashScan V3. In our next article, we will take a look at what’s involved with a remote tune, the process, and the tools needed from EFI Live.