Quote:
Originally Posted by serialk11r
Yes, this is why I speculate that any sort of possible improvement would be very small if existent at all.
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I gave this idea some more thought on my commute home, and have come to a different conclusion.
Recall that the whole point of creating a vacuum is so that air can be effectively metered into the cylinder to vary the amount of generated mechanical energy (which is then used for various things like pumping work and driving engine accessories and overcoming friction and ultimately pushing the car forward). Therefore, for a given power output, the final in-cylinder vacuum must be the same when the intake valve closes, regardless of throttle system being used.
Normal single-throttle systems for gasoline engines use a relatively huge volume, compared to the volume of a single cylinder. This is to provide simple control, and dampens out variations in vacuum created by each cylinder on its intake stroke. However, it takes away some of the mechanical energy from the engine.
For ITB systems, to generate the same amount of mechanical energy per cylinder as the single throttle system, again the final in-cylinder vacuum must remain the same. So, I don't think that the vacuum is necessarily higher with an ITB system, than with a single throttle system. There will still be pumping work associated with an ITB system.
However, at the beginning of the intake stroke for an ITB system, the intake valve opens against a pressure much nearer to atmospheric than with the single throttle. This will make the pumping loop look more like a triangle, as you have hinted at.
Potentially, an ITB system should see significant gains in fuel economy, compared to a normal single throttle system.
Quote:
Originally Posted by serialk11r
I think it would be cool to see data from someone who has swapped ITBs into their car.
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Yes, it would...