Fine Tuning the Engine

Fine Tuning the Engine

When the dyno tuning is complete, it may still be necessary to make some minor adjustments to make the engine pleasant to drive on the road in real world conditions. When fine-tuning the engine for the road, the same principles apply to all engines.

Under full load at all RPM the fuel mixture should be richer than stoichiometric.

  • On naturally aspirated cars, an air to fuel ratio of around 12.5:1 to 13.5:1 is usually best.

  • On forced induction vehicles (turbo or supercharged), the air to fuel ratio may go as rich as 10.5 but should not be leaner than approximately 12.5. Forced induction vehicles may make more power with leaner mixtures, but the excessive combustion chamber heat may cause damage to engine components.

When cruising (light to medium load) the mixture should be as close to stoichiometric (best mixture) as possible and decelerating conditions may allow the engine to be run lean to save fuel. This will result in a particular shape for the map.

Note: All maps for all engines should be relatively smooth. A map with a "lumpy" curve is most likely wrong.

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