SMART TUNER SMT8-C - CAM MODIFICATIONS
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Perfect Power Application Notes. |
Application Note : AN 1 |
Introduction
CRANK and CAM TIMING Background
Technical Considerations
The SMT8-C does not work with ABSOLUTE crank/CAM angles but with differences or modifications. It requires the crank signal as a reference and retard/advances the CAM signals accordingly. Of course, it can also modify the crank signal for ignition timing.
The CAM's are linked to the crank. A much better way to put it is : The CAM's are driven by the ECU to a position signaled by the crank signal. If you are modifying the crank signal to affect the ignition timing, then the CAM timing is affected adversely. Let's assume you ADVANCE the ignition by lets say 3 degrees and you like to maintain the CAM timing. Then you need to RETARD both CAM's by 3 degrees. I am not sure that you notice 3 degree CAM timing, but the point is made.
Of course you can change the CAM timing to any point you like, as long as you consider that the ECU is changing it as well. The following diagram explains it :
It is practical to make an approximate sketch of your particular engine CAM behavior and your desired CAM timing for the exhaust and inlet CAM's and then punch in the numbers in the respective maps.
Very Technical
The following diagram shows how everything fits together.
The CAM inputs have in internal pull-up to +5V and are optimized for 2.5V trigger level. The CAM map entry is in degrees. Positive entries advance, negative entries retard.
An engine with SMT8-C CAM tuning without ignition tuning looks like :