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Originally Posted by Richard L
....I firmly believe that water injection should only be activated when the combustion temperature becomes destructive. Injecting water when your engine is running at an acceptable combustion temperature (refected by the egt ), will loose power and slow down spooling time for sure..
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How very true.
Below is an extract from the excellent book Internal Combustion Engine in Theory and Practice, Vol 1, Second Edition Revised.
I've copied/pasted this from my website.
http://www.max-boost.co.uk/max-boost/intake/WI.htm
Please note that I've only kept the 'core' of the calculations, to make the point clear.
(I have combined and simplified examples 12-3 and 12-4)
Effect of Humidity:
Suppose we have an 8cyl engine producing 300bhp at 4500rpm, 60F and dry air.
Power at humidity 80% and temp 120F (very hot and humid): 230bhp (dry air: 268bhp)
Power at humidity 50% and temp 20F (very cold and humid): 318bhp (dry air: 324bhp)
Note how power is always down when humidity is present.
Another effect of humidity, example 12-5:
Engine producing 300hp, at 100F, humidity zero.
Same engine only produces 243hp, still at 100F but in saturated air.
Here just the effect of reduced air density lost us 57hp, yikes.