[brianhn1]

Originally Posted by Mike@N54Tuning.com

This is a bit of a departure from the thread, but funny that Shiv and Steve want to dig their heels in to the ground and fight about what was essentially a funny comment. The water reduces combustion temps and thus lowers the octane requirements. At the same time it reduces power, due to those lower combustion temperatures, and that oxygen has been displaced by the water. A small amount of water can make a big difference though as evidenced by water injection systems. All tuners know this and setup dyno testing with it to their advantage. Dry air on race gas, higher humidity on pump gas.

Mike

More fuel to defeat, the issue of high humidity recently has been a highly studied issue in engine management. With the EPA mandating lower CO2 emission requirements these coming years, manufacturers are developing more powerful catalyst converters that require EGT to be above a certain threshold for optimal effectiveness. Under high humidity conditions, the engine will either lean the fuel mixture or retard the timing further under low load conditions to compensate for the reduced EGTs. Obviously our N54s don't have a humidity sensor so this sort of logic is not implemented. We will definitely see it in newer cars.