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).
FlashScan's scan tool incorporates...
FlashScan's scan tool incorporates a virtual dashboard that can be easily customized. You can specify either analog or digital gauges, or a combination. Fittingly, virtually every aspect of the virtual dashboard can be altered. A few tuning issues are evident in this particular display. The VE table needs some adjustment because commanded air/fuel ratio is 12.96:1, but the LM1 wide band is reporting 13.3:1. Also evident is a potential fuel supply problem. Pulse width is shown as 18.250 milliseconds at 5,700 rpm. With only 20 milliseconds of time available at 6,000 rpm, the injectors are too small for the amount of power the engine is producing.
Page B of the virtual dashboard...
Page B of the virtual dashboard displays data in strip chart form. The values displayed at left and right correspond to the cursor position. The values at the current cursor position are also displayed on Page A
The white highlighted area...
The white highlighted area on this chart was created by clicking and dragging the cursor on a strip chart. When you do this, the digital values show maximum, minimum, and average values for the highlighted areas. The appropriate cells in the related tuning table are also highlighted.
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).
When FlashScan is plugged...
When FlashScan is plugged into the underdash diagnostic test port, the display illuminates and displays a number of options, which can be selected by depressing one of the function keys (F1 through F4). Ultimately, it will be possible to read and reflash a PCM directly from the unit with no laptop connected. Data can be stored internally or on a secure data memory card.
The FlashScan unit incorporates...
The FlashScan unit incorporates a number of ports to which external data acquisition equipment can be connected. Wide-band O2 sensors are the most commonly used devices, but K-type thermocouples and virtually any other 0-5 volt sensor can also be connected. The scan program can then be set up to record data from these devices, and display it on the same virtual dashboard as data from the original equipment sensors.
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.
| DIFFICULTY INDEX ::: ||NNN |
|ANYONE'S PROJECT | no tools required || N |
|BEGINNER | basic tools || NN |
|EXPERIENCED | special tools || NNN |
|ACCOMPLISHED | special tools and outside help || NNNN |
|PROFESSIONALS ONLY | send this work out || NNNNN |