Back in "the old days" (2002-2003), the process for tuning a C5 was considerably more intricate than it currently is. At that time, you had to use one program to log and analyze data, and another to reflash the PCM with a new calibration. Tuning was a relatively tedious process because the two programs didn't "talk" to each other. Consequently, you found yourself continually switching back and forth between programs to determine the changes that had to be made. To make matters even more challenging, none of the programs available at the time were particularly user friendly.
Then I came across a scanning/data logging software package called EFILive. It was not only easy to use and to customize, it offered a number of unique capabilities, including a control panel that allowed the user to temporarily alter ignition timing, air/fuel ratio, and torque converter clutch lock/unlock settings-while the engine was running-with a laptop computer.
I hadn't used EFILive for very long before thinking, I wish these guys would develop tuning software. In early 2005, my wish was granted when the EFILive team of Paul Blackmore and Ross Myers released FlashScan, version 7.2. They followed that up with version 7.3 and have continued to add features to it, including the capability to scan and tune LS2/LS7, GM diesel, and four-, five-, and six-cylinder GM engines. Recently, they released version 7.4, which provides even greater scanning and tuning capabilities, and can be used with an even wider selection of General Motors ECMs and PCMs.
A fully integrated software package, FlashScan includes separate scanning and tuning programs, which operate independently but also interface with each other. This extremely well-done interface, which can be easily altered to accommodate individual user preferences, tremendously simplifies the task of implementing tuning changes based on data logged during testing.
To make tuning even more interesting, in late 2006, EFILive released its V2 interface cable that will ultimately allow stand-alone scanning and tuning (without requiring a laptop computer). The V2 cable also accepts data from up to eight external inputs, such as a wide band O2 sensor, thermocouple, or a variety of temperature or pressure sensors, or any analog sensor with a 0-5 volt output.
All LS1/LS2/LS6/LS7 tuning software does pretty much the same thing-it allows you to make changes to a vehicle's calibration data and write that data to the PCM.
What makes one program superior to another is ease of use, documentation, and the extent of changes that can be made to an existing calibration. In these areas, FlashScan is in a league by itself. No other data logging/programming package offers access to over 650 calibration parameters and tables combined with data monitoring and logging capabilities, the ability to link logged data with relevant calibration tables, and a control panel to make temporary changes on the fly.
Although electronic powertrain controls are often regarded as having almost magical capabilities, they simply offer more extensive and precise control of engine and transmission calibrations than nonelectronic mechanisms. Tuning, therefore, is as much a matter of learning to "control the controls," as it is a matter of developing the data that will enable the engine and transmission to deliver optimum performance. With FlashScan providing access to so many control parameters, it's relatively easy to gain control of virtually any aspect of powertrain operation. FlashScan also facilitates the development of the precise calibrations that are required to achieve specific results-such as establishing the fuel, spark, and air flow settings that enable an engine with a radical camshaft to idle as smoothly as possible.
The tuning process itself typically begins with a data logging session to determine the settings that need to be changed. That information may be monitored in real time on FlashScan's virtual dashboard and stored for future playback. The program is supplied with several default dashboards, including one with "Imperial" and another with metric data. These may be easily customized to display virtually any parameter in either measurement system, or a combination of both. As an example, if you want to display air flow in grams per second and inlet air temp in degrees Fahrenheit, all you have to do is set up the appropriate Parameter Identifier (PID) and dash gauge accordingly.
It's also possible to add special PIDs and gauges to display calculated data or data input from an external device-such as a wide-band oxygen sensor. The latter is essential for properly altering fuel flow to achieve air/fuel ratios other than stoichiometric (14.7:1). Although wideband sensor systems, such as Innovate's LM1, include stand-alone data logging capability, the relevance of air/fuel data is much easier to see when it's included in the same log that contains all the relevant PCM/ECM data, such as pulse width, manifold absolute pressure (MAP), and air flow data. If stand-alone data logging/monitoring is not required, Innovate's LC1 is preferable because it's less expensive and is better suited for permanent installation and use with a system like FlashScan.
The process of using logged data to revise PCM calibrations can be long and tedious, but FlashScan's linking capabilities significantly streamlines the process. When you open a stored data log and move the cursor to a position within the recorded chart, the "coordinates" of that point are highlighted on the relevant calibration data table and/or graph within the tuning program. As an example, if you move the cursor along a recorded data graph to a position where spark knock is indicated and then click over to the spark map in the tuning program, the cell that corresponds to the engine rpm and engine load, when the knock occurred, will be highlighted. The contents of that cell can then be changed to a lower value that will not precipitate spark knock.
Similarly, if you move the cursor to a position where excessive fuel trim is indicated, or where the wide-band O2 sensor indicates the actual and commanded AFR are off a good amount, the appropriate cell in the VE map is highlighted. It's also possible to "click and drag" across a data chart to highlight a range of data points. When you switch from the scanning to the tuning program, all the cells that relate to the data points on the graph are highlighted. This capability eliminates guess work as to which calibration values relate to actual operating conditions and greatly simplifies tuning.
Unfortunately, EFILive's extensive capabilities can't guarantee that an engine or transmission will be optimally calibrated, or that a drivability problem will be resolved. The power to accomplish those goals reside with the person operating the keyboard. If you've paid to have your C5 or C6 tuned and weren't happy with the results, you know first-hand that the ability to operate tuning software doesn't guarantee the ability to properly tune an engine.
To be fair, some tuners don't hit the required marks because the software they use is a bit too cumbersome. If certain tables are too difficult to access, or aren't available, the tuner is left with no recourse other than attempting to apply a variety of band-aids because he can't fix a particular problem properly. This is a fairly common scenario when attempting to obtain decent idle quality after an aggressive camshaft has been installed.
Typically, desired idle speed has to be increased as does desired air flow (at idle). The question is, how much? Determining idle speed is easy enough- 800-900 rpm usually provides acceptable idle quality with cams designed for street-driven vehicles. But achieving a relatively smooth idle within that rpm range, and a smooth transition from idle to part throttle under load (as when accelerating) requires adjustments to a number of tables including desired air flow, spark timing, and throttle follower. Finding the optimum settings can be a bit tedious, requiring a lot of trial-and-error testing (with error being the operative term).
EFILive's scan program control panel is a useful tool for eliminating some of the trials and the resulting errors. The changes made through this panel are effective only while it's open, and the desired function is active, but the information can be used to subsequently alter settings through the tuning program. As an example, you can vary timing settings up and down while you monitor idle quality. Then you note the setting that produced the best idle quality and enter that in the appropriate position within the timing map.
Similarly, many of the calculated parameter identifiers or PIDs found in the scan program simplify identification of changes that are required to optimize performance. In the case of idle quality, you can access four PIDs that display the amount of air-flow correction being applied by the system to achieve the specified desired idle speed (correction with transmission in gear, air conditioning on, air conditioning off; transmission in park/neutral, air conditioning on, air conditioning off). By logging the appropriate PID you can see the amount of air flow increase or decrease being applied by the operating system. That provides a guide for determining the optimum setting-simply add or subtract the logged correction values to the current settings in the Desired Airflow Table, and the new values will reduce air flow corrections to a minimum, and the engine will idle as smoothly as the camshaft will allow (providing fuel and spark settings are on target).
Another superb aspect of EFILive is the availability of custom operating systems. Although custom operating systems can be used with stock engines, they're designed to address the challenges of tuning engines equipped with radical camshafts, are turbocharged or supercharged, or are equipped with a nitrous-oxide system. Features include VE table scaling for two- or three-bar map sensors, the capability of eliminating the mass air flow sensor and operating in true speed density mode, a VE table that references throttle position instead of manifold pressure, and a "valet mode" to limit engine speed when drivers of questionable judgment are behind the wheel.
In spite of some people's opinions to the contrary, you can't tune a C5 or C6 effectively if your departure from the turnip truck has been fairly recent. However, if you understand the basics of internal combustion and spend a few evenings learning how to operate FlashScan (reference information and a number of tutorials are included with the package), you'll be able to start tuning in short order. But before you make any changes, download and store the original calibration from the PCM or ECM. That way if your trials are filled with errors, you can easily revert to the original calibration and try a different approach.