- #1
thender
- 39
- 0
Hello all,
I am studying four stroke ICE engines (as a mechanic) and there is something I can't fully understand about the combustion process.
It's repeatedly documented in books that retarding the ignition timing will reduce cylinder temperatures / avoid engine knock.
Though less consistently it seems to also be said that further advancing ignition timing will lead to greater power output.
It's also said that approximately 1/3rd of energy from the fuel is lost through the exhaust and 1/3rd through the cooling system.
So my problem is I don't understand why it seems that advancing ignition timing increases cylinder temperatures and heat to the cooling system and retarding timing appears to increase the heat in the exhaust.
What I believe is that the sooner the mixture is ignited the higher the pressure in the cylinder will be during the time when the piston is rising against and pushing down from the combustion. Whereas if the ignition is later then less work is done because the piston is already more headed down and the remaining fuel air mixture burns as it travels out the exhaust.
Some others have claimed it has to do with the cooling passages around the area of the combustion, like whether the flame burns more toward tdc or lower in the engine block.
So my question is how does ignition timing affect the heat distribution and useful work achieved, does it split the energy between exhaust and engine and why?
Thank you,
Andrew
I am studying four stroke ICE engines (as a mechanic) and there is something I can't fully understand about the combustion process.
It's repeatedly documented in books that retarding the ignition timing will reduce cylinder temperatures / avoid engine knock.
Though less consistently it seems to also be said that further advancing ignition timing will lead to greater power output.
It's also said that approximately 1/3rd of energy from the fuel is lost through the exhaust and 1/3rd through the cooling system.
So my problem is I don't understand why it seems that advancing ignition timing increases cylinder temperatures and heat to the cooling system and retarding timing appears to increase the heat in the exhaust.
What I believe is that the sooner the mixture is ignited the higher the pressure in the cylinder will be during the time when the piston is rising against and pushing down from the combustion. Whereas if the ignition is later then less work is done because the piston is already more headed down and the remaining fuel air mixture burns as it travels out the exhaust.
Some others have claimed it has to do with the cooling passages around the area of the combustion, like whether the flame burns more toward tdc or lower in the engine block.
So my question is how does ignition timing affect the heat distribution and useful work achieved, does it split the energy between exhaust and engine and why?
Thank you,
Andrew