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Old 08-27-2010, 04:37 PM   #6 (permalink)
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DFCO is employed because when you are engine braking the effective compression is very low, and any fuel injected into the engine has a very good chance of not igniting and being exhausted with very high amounts of unburned hydrocarbons, as well as damage to the converter when the unburned fuel passes through the converter.

With manifold vacuum of higher than 22 inches, the amount of air in the cylinders is only a small percentage of the amount that would create the designed compression ratio. This is a recipe for misfires.

Determining if your car has DFCO is easy, just let the car slow down in gear until you feel the fuel injection engage and the car will either stop slowing down altogether or slow down at a much lower rate. The point is easy to feel.

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