Brother here is the explanation for you that the phenomenon is called The Law of Heat Exchange in the field of thermodynamics. The reason you're seeing water coming out of the tailpipe is that the petrol is combusting at very high temperatures in the chamber (I'd imagine this would be varying temperatures based on engine design, and according to the heat engine model, a hotter temperature engine is more efficient) and the gases are cooling down as it leaves the pipe. Now the exhaust system is hot, don't get me wrong, but it's nowhere near as hot as the gas coming out of the pistons, which is the main source of the heat in the first place.
Since the gas coming out of the engine is fully saturated with moisture, any drop in temperature will cause the water to precipitate out. A cold winter's day is going to amplify this effect and this will continue till the temperature of the exhaust pipe is nearly equal to that when it first left the chamber. I hope it’s simple enough now to understand the chemistry/ physics behind it.
Friend Zulfiqar asked if we idled the engine for 8 hours??? Where in the highlighted text I used the word IDLE? I said static running. Now what difference does it make if I idle the car for 8 hours or I rev it for 8 hours or anything in between while its stationary when the end result is that I am getting 15.3KM/L combined average which is 99.9% of the reported factory average. If anybody still thinks that piston rings have not seated well, that head will cause low compression and power loss and static running is a bad practice then surely it would not be an efficient engine, but it seems our build has thrown a lot theory right out of the window.
I will be blunt here, the only technical detail I could share, I already have; that the head is the same. Since the car has been delivered, I think there is no point in making a mountain out of a mole hill. If in any case our work has left bemused looks and more questions than answers, well that is a prize in itself.
