somewhat similar to the decrease in engine braking in diesels because of the absence of a throttle plate Bone?
because of this:why all that?
in addition to the tune, if I can make the car coast for a longer distance with my foot off the gas and / or lose less speed while coasting, it wouldn't hurt. the trick as far as I see it is to stop the ECU from squirting fuel while keeping the throttle wide open, which should be achievable with a bypass valve and ignoring MAP input.http://en.wikipedia.org/wiki/Engine_braking said:The term engine braking usually refers to the braking effect caused by the closed-throttle partial-vacuum in petrol (gasoline) engines when the accelerator pedal is released. While some of the braking force is due to friction in the drive train, this is negligible compared to the effect from the vacuum.
When the throttle is closed, the air flow to the intake manifold is greatly restricted. The concept can be illustrated by the amount of effort required to blow/suck through a thin tube vs. a thicker one. It is the work the engine has to do against this restricted air flow that provides the braking effect.
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Diesel engines
Diesel engines do not have engine braking in the above sense. Unlike petrol engines, diesel engines vary fuel flow to control power rather than throttling air intake and maintaining a constant fuel ratio as petrol engines do. As they do not maintain a throttle vacuum, they are not subjected to the same engine braking effects.