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Discussion Starter #1
On older cars with iron engine blocks I have sprayed a mist of water/ droplets into the inlet to decoke the combustion chamber. I have done this on the Alfa V6 but thought that I should stop as the Alfa v6 is an aluminium alloy block and head. Thus it has a lower melting point than iron. I am also assuming that the compression is a little higher than on older engines.

I want to decoke my engine with water but worry that the extra heat generated from the water and higher compression might damage the block and heads of the Alfa.

Anyone with any thoughts? Experience?
All thoughts are welcome.
 

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Why do you think there would be extra heat from the water? Surely as the water vaporises in the cylinder it would absorb heat and cool the cylinder down. The Latent heat of vaporisation of water (energy required to convert liquid water to vapour) is huge.
 

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Isn't that the same principle that water injection uses on forced induction cars? A fine mist sprayed into the intake to cool the charge to increase air density, and by doing so also lowering piston and combustion chamber temperatures, so by that reasoning it should be fine I'd have thought. I'm no engine technician though!

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Discussion Starter #4
I was assuming that water being partly composed of oxygen, would add more combustion to the combustion generated by the petrol. So extra air added to the fuel air mixture would create a lean mixture. A very lean mixture creates extra heat.


I understand that the latent heat required to turn water into vapour is huge. Would the initial explosion from the spark and petrol provide this extra energy?
 

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I was assuming that water being partly composed of oxygen, would add more combustion to the combustion generated by the petrol. So extra air added to the fuel air mixture would create a lean mixture. A very lean mixture creates extra heat.


I understand that the latent heat required to turn water into vapour is huge. Would the initial explosion from the spark and petrol provide this extra energy?
The reason that the fire brigade use water to put out fires is that it absorbs so much heat from it's surroundings in vaporising. In your cylinder it would absorb heat from the ignition flame front and the cylinder walls.
The oxygen in water is very strongly chemically bonded to the Hydrogen. You would need much higher temperatures than exist in an engine to break that bond and free up the oxygen. Whereupon it would instantly react with the Hydrogen to form water.
 

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Well it's confession time, I have tried this system, I noticed that my sons MG had very clean combustion chambers, inlet and exhaust track when I changed the head gasket. The piston crowns where like new, I put it down to coolant ingress (that was why the head was off). So I tried it on my JTS, set the car to run at a high tick over <>1500 rpm, removed the inlet pipe and cleaned to throttle body, then sprayed water into the throttle body. There was evidence of stream coming from the exhaust and the exhaust pipe was noticeably cleaner. When I put a scope down the plugs holes, there was no doubt that the crowns were cleaner. It was an interesting experiment, did it make a difference, I am not sure, did the car go OK, yes indeed, it took me all over Europe many times and is still going strong (new owner).
 
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