Quote:
Originally Posted by Circlotron
If ambient air temp is 30 deg C and it gets warmed to 60 deg C, an increase of 30 deg, if that increases combustion temp by 30 deg then that is not going to do a lot as regards NOx. If it increases combustion temp by more than 30 deg then you have gained something thermodynamically. (excluding the energy consumed in additional NOx production) Thermal losses to the coolant would have to be extremely nonlinear for this increase to produce an overall loss. If that were so, cooling peak flame temp marginally instead of increasing it would produce worthwhile increases in overall thermal efficiency.
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When it comes to NOx, warmer IAT cause the charge to increase in volume. This in turn displaces EGR and increases NOx. Its also why photo chemical smog happens in summer.
When it comes to efficiency lets look at a diesel engine so that we isolate any effects such as throttle for a moment. The changes in efficiency are measurable and due only to thermal loses to the block and cooling system.