EFI 102 “Understanding EFI Processes Through Detailed EFI Sub-system Analysis”
by Christian Krahenbuhl
This is the second of four EFI articles from Cobb Tuning. This article will provide a more precise focus on modern EFI Systems; introducing you to various closed-loop control systems and explain how some of the basic calibration/tuning feedback systems are used. We will again introduce you to the new terminology and rhetoric used by tuners, engineers, & engine calibrators. This article will use more advanced animations and hands on exercises (with a spreadsheet) to educate you as to how calibration of modern EMS is done. We will breakdown the EMS into sub-systems; we will look at separately understanding and calibrating the Fuel System, the Ignition Advance System, the Boost Control System, the Camshaft Phasing System & Other Control Systems.
Many think that modern EMS is too complex…which is not the case. Modern EMS has not changed much since the mid 90’s so have no fears about something being too complex. Simply take the time to break down the entire EMS into various sub-systems, then sub-components from there and the bigger picture becomes much more simplified. How fuel is injected or spark is delivered has not changes significantly for several decades so relax and enjoy the ride.
Below is some additional common vocabulary, acronyms, terms, & rhetoric used in EMS tuning…and how they are used in EMS calibration. Some of these variables are not available in every vehicle; they are only available in specific vehicles.
ATDC – An acronym for After Top Dead Center, which is usually referring to crankshaft degrees.
Algorithm – A finite set of well-defined instructions set-up to process data by taking a given input and terminating to an output. The algorithm is essentially how a computer processes information.
BTDC – An acronym for Before Top Dead Center, which is usually referring to crankshaft degrees.
CI – Compression Ignition diesel or gasoline engine.
Closed Loop System – An EMS sub-system which has a dynamic ability to trim (or modify) its performance based on feedback from various sensor inputs.
DISI – Direct Injection Spark Ignition internal combustion engine.