| There is a better way of looking at this I think. The reason the turbo charts are calibrated in lbs/min is It is a constant. If I can hypothesize a bit. If we assume 1000 air molecules weigh 1 lb. It doesnt matter wether the space they take up is a cubic foot or a cubic inch they still weigh a pound. The amount of pressure they are being subjected to really only determines the volume of those molecules. They still weigh the same. So if we look at the exhaust manifold temp (and we all know that as air heats up the molecules vibrate more so the volume of the gas expands) At say 21 PSI and 500degrees F and look at the volume of air that 1000 molecules of air inhabit. It is different to the air volume that the molecules would inhabit at 900 degrees F. Therefore the lower the temperature of the exhaust charge (due to the free flowing nature of the engine/manifold) the more air molecules it can pass per minute. Meaning the same amount of power at lower boost levels. This why the lbs/min axis on the turbo graph is more relevant and is used instead of PSI even though its harder to quantify to us in the real world. Its a constant independant of temp.
If we have
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