Note: Valve timing for the Dual Intake Engine could not be maximized in the same way as the baseline engine. For in the case of maximum horsepower valve timing would favor the high pressure air to a point where thermal efficiency became unexpectedly low. And in the case of maximum thermal efficiency the low pressure air was favored to a point that the engine power output became significantly lower than the baseline engine.

It is not real evident by the PV diagram due to the scale, but it is true that the Dual Pressure Intake Engine does not benefit from positive pumping work to the extent that the baseline engine does. But why should useful work be "pumped" back into and engine where some of that work is lost to friction?

Anyway the dual intake engine has at least 4 things going for it that on the balance make it a more efficient engine.

1) Due to the lower boost of the one compressor, less of the work from the turbine will be consumed. And since this engine's turbo shaft is connected to the crankshaft this remaining work can be considered useful work.

2) The "low" pressure air will be coming in at a lower temperature since it will have experienced less compression heating. So after the "high" intake air enters the cylinder it will result in a higher volumetric efficiency due to the fact the air will be denser due to the lower temperature of this mix. This will improve indicated work by a higher percentage than any increase in friction losses.

3) Also this low temperature mix will result in a lower maximum temperature, reducing heat losses to the cylinder walls and thus improving thermal efficiency.

4) This is not accounted for in the simulation program. But it is thought that swirl and turbulence of the intake air should be greater at the time of combustion helping improve the combustion efficiency and the burn rate. This high kinetic action should occur since a higher portion of the induced air enters the cylinder later in the cycle and at a higher velocity due to the high pressure differential between the cylinder and intake manifold.

Importance of Uniport Valve

In the simulation for the baseline H series engine the intake port area was equal to 22.47 in². In the dual intake engine simulation there was 19.87 in² for the low pressure gas and 11.36 in²for the high pressure gas. So, the dual pressure intake engine had 39% more port areas than the baseline H-series engine.

So though it is possible to have a dual pressure intake engine without using a Uniport Valve it would reduce the power rating of an engine significantly.