BMW: Water Injection Can Boost Power And Cut Fuel Consumption

[Occasionally6]

Originally Posted by Daox

I'd imagine they'd have a 'low water' light. If you run out of water, they'd really have to retard timing I would think to avoid knock.

Maybe just drop the boost pressure?

I honestly can't see the A/C system providing that much water, but I could be wrong. Also, that fuel efficiency increase is really going to take a hard hit if you have to use the A/C to refill the water supply.

From a psych chart, here:

https://lehighcheme.wordpress.com/20...etric-chart-2/

If the ambient air is at 25C and 60% RH and cooled to 5C there is ~12g - ~6g of water available per kg of air.

The heat energy that the A/C has to extract is ~56 - ~18kJ/kg. The power required is that figure divided by the A/C's COP and multiplied by the (in)efficiencies.

At 1.225kg/m^3.

How much water is needed?