Quote:
Originally Posted by Patrick
Please explain how the engine increased torque with the same amount of air.
Also, please explain how the engine (a positive displacement pump) pulled in the same amount of air at a lower rpm with the throttle plate at the same position.
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The volume [displacement] of air is the same for every cycle and at all rpm. What changes is the mass of the air in the cylinder when the intake valve closes. The mass of air is controled by the throatle plate in spark ignition engines, therefore if more torque is produced the throatle plate should have to be more open [less restiction].
To produce the same amount of power the engine must consume the same mass of of air and fuel with the same thermal efficiancey at the lower and higher rpm. So the volume of air is directly proportional to the rpm the mass is changed by the throatle plate.
The only thing that changes is the amount of time [longer] the intake valve is open at the lower rpm so with the same rate of flow [mass] past the throatle plate the longer time would allow a greater mass of air to enter the combustion chamber. The question that I don't know the answer to is; is that enough to raise the torque as much as is needed to produce the same amount of power, I some how doubt it. So unless the time difference is enough then the plate has to be less restrictive [more open] to allow the same mass of air to enter the engine at the lower rpm.
Do I have it right yet?
