I agree with Kona about the stoichiometric combustion tempterature, here is a graph showing ideal Temperature & pressure for the 2 adiabatic combustion types. A 4 stroke engine is a constant volume adiabatic combustion process.
http://en.wikipedia.org/wiki/File:Flametemp.jpg
I disagree about the speed of combustion however and the timing adjustment required. A lean mixture is far more prone to pre-ignition than a stoichiometric one. A lean mixture tends to burn more quickly or even detonate.
The timing of the engine is set taking into account the speed of combustion for a stoichiometric mixture in order to develop maximum pressure as the piston is just a hair beyond TDC. By burning the mixture faster and sooner the max pressure from the combustion charge occurs BTDC.
Pre-ignition is what gives you the 'pinging' or rattling sound - which we all know is a symptom of something bad happening in the engine. In order to reduce the effects of pre-ignition one needs to retard the timing.
Also the fuel charge in the air mixture has greater enthalpy than the air in the mixture and cools the piston head, valves and valve seats. When you don't have as much fuel in the mixture you don't get that cooling and therefore those engine components run hotter.
Due to the timing of the valves there is an overlap between the opening of the intake and the closing of the exhaust valve. So some of the intake charge, unburnt and cooler, goes out the exhaust port and cools the exhaust port and reduces the temperature of the exhaust header slightly. With a lean mixture the heat builds up and you see it in the greater extent of bluing in the header.
A race ECM is a good place to start, it will help the engine run better and produce more power, but I would also check my intake for leaks just in case…
http://en.wikipedia.org/wiki/File:Flametemp.jpg
I disagree about the speed of combustion however and the timing adjustment required. A lean mixture is far more prone to pre-ignition than a stoichiometric one. A lean mixture tends to burn more quickly or even detonate.
The timing of the engine is set taking into account the speed of combustion for a stoichiometric mixture in order to develop maximum pressure as the piston is just a hair beyond TDC. By burning the mixture faster and sooner the max pressure from the combustion charge occurs BTDC.
Pre-ignition is what gives you the 'pinging' or rattling sound - which we all know is a symptom of something bad happening in the engine. In order to reduce the effects of pre-ignition one needs to retard the timing.
Also the fuel charge in the air mixture has greater enthalpy than the air in the mixture and cools the piston head, valves and valve seats. When you don't have as much fuel in the mixture you don't get that cooling and therefore those engine components run hotter.
Due to the timing of the valves there is an overlap between the opening of the intake and the closing of the exhaust valve. So some of the intake charge, unburnt and cooler, goes out the exhaust port and cools the exhaust port and reduces the temperature of the exhaust header slightly. With a lean mixture the heat builds up and you see it in the greater extent of bluing in the header.
A race ECM is a good place to start, it will help the engine run better and produce more power, but I would also check my intake for leaks just in case…
