I would like to hypothesize on the potential results of installing a smaller crankshaft pulley. Please tell me where my reasoning is wrong and please forgive my long-winded stream-of-thought post.
Smaller crankshaft pulley = slower accessory belt speed. This amounts to less rotational energy available for the devices which use this energy, and more for vehicle propulsion.
1. Slower alternator, but unchanged electrical load means the alternator now must work harder to provide the same energy required. Whatever electrical needs the vehicle has is provided by the alternator - the voltage regulator will adjust the field voltage to compensate. This limits the amount of power the alternator is able to deliver. This has implications beyond the typical high electrical loads such as headlights & A/C operation - think of potential safety concerns such as anti-lock brake & electric steering assist operation. No gains will be found here unless the electrical load is reduced, which does not require a change in rotational speed. It would be helpful to find operational specifications on the alternator, such as maximum amperage generated at any given RPM. The alternator may reach it's peak output at a given RPM and faster rotational speed will have no affect (but not necessarily draw more or less energy.)
2. Slower A/C compressor speed may free up more energy for vehicle propulsion, but similar to the alternator, the A/C compressor still has a load which isn't affected by the change in accessory belt speed. The compressor will either run for longer periods of time or fail to keep pace with it's requirements. Again, no energy gains to be found. However, having the A/C compressor cycle less does have a certain appeal...
3. Slower water pump speed may result in more energy available for vehicle propulsion but at the expense of engine cooling. While the radiator may be able to dump whatever excess heat it is designed for it cannot do it as effectively if this heat isn't delivered & passed through with the same velocity.
The details for heat transfer such as air conditioning and engine cooling are better described by someone more versed in that subject. It is my understanding that faster velocity in terms of fluid flow (both coolant in it's liquid state and air in it's gaseous state) improves heat transfer but somewhere one reaches a point of diminishing returns.
I'm impressed with the efficiency of the Mirage platform as it is and wonder if Mitsubishi engineers thought all this out already.
Probably not. It is, after all an economy car.
View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)