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Following this, move on to the Engine Diagnostics. Here you can deactivate the diagnostic routines for the catalytic converters (we removed them so they don't create a fire hazard during extremely hard running at the track), the rear O2 sensors, the MAP/MAF airflow correlation tables and of course the misfire diagnostics. Any cam with even a medium amount of valve overlap can cause enough rumble and shake at idle to trick the ECM into falsely detecting an engine misfire. It's best to leave as many diagnostic routines on as possible to make diagnosing problems or issues easier, but with some mods, such as mild to wild cams and open exhausts, many diagnostic routines simply must be deactivated. Below is an example of the modifications made to the MAP/MAF correlation parameters as well as the Catalyst and Post O2 tests.

‚ÄčThe next steps you'll need to take before tuning a cammed engine is to modify the Torque Management and Engine Diagnostic tables and parameters. Torque Management is simple enough: If you look at the illustration below, you can see that you click on the Engine tab, then Torque Management (bringing you to the screen show, and then click on the Max Torque buttons, modifying from 1st Gear through 6th Gear. In the window below you can see that the 1st Gear button has been selected and all of the values have been modified to the maximum allowable 6,042 lbs/ft. This will prevent the ETC or spark timing from interfering with maximum potential engine torque output, but it will not disable Traction Control. Should the Traction Control sense that the rear wheels are spinning (and of course the driver has not manually deactivated TC), the ECM can still command reduced spark advance or close the throttle to prevent rear wheel spin. All of the benefit of power, none of the fright should you choose to let lesser driver's take a crack at the wheel.

With the new long-duration/high-lift cam, you can expect manifold vacuum levels to tank pretty badly at idle speed and up through about 2,000 RPM. This is simply a function of intake air flow reversion due to valve overlap and there's nothing you can do to prevent this. It's just plain physics. Bumping up compression ratio helps, but only so much as the cam timing is what it is. This being the case, you must modify the spark advance at idle to get cylinder pressure back to where it does the most work (about 7-15 degrees ATDC). If you leave the ignition spark advance tables in stock form, the ECM won't command enough spark advance at lower engine speeds and higher loads. This can result in miserable fuel economy, lower-than-necessary power output, the exhaust valves will run excessively hot, etc. Since we added extra airflow through the Airflow Final Minimum table, we don't necessarily have to run too much spark advance at idle speed and low load, but we will need more ignition advance when at idle and higher loads (think added electrical system loading with additional alternator torque requirement, air conditioning, power steering loads, engine deceleration while at a stop in the pits, etc). The following tables can give you a head start. You'll see the actual values we started with along with the difference of the values as seen in the "Show Differences" window of the HP Tuners Editor software (yes, extremely handy feature, this). The factory settings work great for a stock cam that has little valve overlap and good manifold vacuum, but for any mild to wild cam, you not only won't hurt the engine with more spark advance at idle speed, you will in fact need it as the dynamic compression will be lower and the fuel mixture will take longer to burn.

TUNING

LS7 - CAM - Page 2