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Power Enrichment Operation 
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Joined: Tue Jan 15, 2008 2:31 pm
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Contrary to the beliefs of some ignorant engine management developers, it IS possible to be at the same airflow (measured or inferred from MAP) at different throttle openings. Also contrary to these buffoons thoughts, there is not a single optimum AFR/timing combo for each given load/RPM site. Nor, for most of the load/RPM range, is there a single reliable AFR/timing combo. Most engines will run acceptably over a range of conditions at any given load/RPM site.

There are in fact two, in some cases mutually exclusive, optimums:

  1. Optimum torque/power (minimise BSAC)
  2. Optimum fuel efficiency (minimise BSFC)

Each of these is a precise tuned point, for a specific load/RPM combination, and 3d curve, in general. Each, therefore, requires both a timing curve and lambda curve as a matched pair. How does one, or the EMS, know which tune to use at any given time? Driver input! This can come in several forms, most obviously the TPS and/or a dedicated PE switch. Switch operation is somewhat obvious and the most basic of table switching implementations. In terms of using the TPS input for controlling this, a single 2d RPM vs. TPS % table with some hysteresis is required too.

Regardless of whether you're running MAP, Alpha-N (switch only), or MAF derived load/airflow, this feature is applicable. It is, however most certainly to be considered fine-tuning and/or optimisation. Therefore, it won't get implemented until someone shows me a near perfectly tuned VE table or MAF calibration, with logs across a wide range of conditions. Of course, such a tune and log have as a prerequisite a perfect sensor and solenoid (injector) configuration.

But everyone always says one tune gets you both economy AND power, are you saying that it's not true??? Because the vast majority of standalones never get fine tuned to this extent, and because the majority of the engine operating areas are only attainable with a single throttle input, you might have heard people, including me simplify the situation slightly. The reality is that without this feature you CAN get excellent economy AND excellent power, all you lose is either some part throttle torque in some areas, and/or some part throttle economy in others.

PS, it took me 1.5 hours to write this tapping away with one hand at a snail's pace :-/


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Sun Jun 03, 2012 5:45 pm
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