Quote:
Originally Posted by SaxoVTRacer
the lamba sensor sits in the exhaust before the cat and controls how much fule is injected into the engine by readign the 02 / oxygen levels in the exhaust system using alpha radiation, its tells ur engine if its got too much fuel in the zorsta dn thats why u do more miles on high octane as the lamba adjusts the ecu to spray less petrol making it more efficent
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Careful, you started off OK there but...
The lambda sensor is situated in the exhaust manifold, and its purpose is to send air / fuel ratio signals back to the ECU. You don't have fuel in the exhaust... Your ECU will be programmed to run at a specific AFR, so if the lambda believes the mixture to be too lean or too rich, it will instruct the ECU to adjust to suit.
Higher octane fuel doesn't mean that the lambda sensor will "adjust the ECU to spray less fuel." If this were the case, the engine would run lean, and then potentially overheat, melt the pistons and die and pathetic death. Performance can be gained from higher octane fuels because of the fuel itself being LESS combustible believe it or not. In a simplistic view, a less combustible fuel (high octane) when mixed with air, can be pressurised greater than a normal octane fuel. If used correctly, for exmaple, adjusting / advancing the ignition timing to generate a greater air / fuel pressure in the combustion chamber, (if possible) will allow for a greater energy release upon detonation. The reason that a lower octane fuel cannot be pressurised as greatly, is because of the likelyhood of pre-detonation. This is where the air / fuel mixture becomes unstable during the compression stroke, as the greater the pressure, the more volatile the mixture becomes. As mentioned earlier, the higher octane fuel (less combustable) allows for a greater increase in the compression of the mixture before pre-detonation may occur.
