How do engines detect higher octane fuel?

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  1. How do engines detect higher octane fuel? 
    #1
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    Greetings,

    I understand how engines can detect knock and then reduce the timing, that makes perfect sense, like if you put low RON grade fuel in and it knocks, it can detect this and reduce the timing to compensate. What I struggle to understand though is how it increases the timing when you fill it with super unleaded 99 RON. I've read that it takes a couple of full tanks before the timing adjusts, but how does it know you're using higher grade fuel? Does it gradually try to increase the timing in minute amounts every now and then and see if it works without knocking? This kind of trial and error approach which would inevitably cause knock at some point just doesn't make sense in my head.

    Enlighten me?
     
     

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    I used v-power for about 9 months straight only noticed approx 30 extra miles per tank compared with normal unleaded i think if you remap then running v-power might see performance gain

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    Thanks, doesn't really answer my question though I use vpower too because I want more performance, I just want to understand technically how the ecu figures out that it can advance the timing for higher octane.
     
     

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    Im not 100% but i think they have two standard ecu maps which enables the car to switch when higher ron unleaded is used best talking to the tuners in that section

    End tuning hes clued up he was explaining it all the other week to me on the phone good fella

    When u say more performance what are you expecting by using super unleaded exactly?

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    I'm not expecting anything, like I said I just want to understand how the adjustment is made by the ecu for higher grade fuel. It makes sense technically that it can retard the timing when knock is detected, I just can't figure out how it does it in the other direction.
     
     

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    Not sure but I think the lambda sensors will tell the ecu.
     
     

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    That's vague.. what are lambda sensors and how do they work? I want to understand the process in detail
     
     

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    pretty sure its the engine knock sensors that detects the fuel type from the engine detonations of the fuel...as it suggests the poorer the fuel quality the more it will rattle and knock and the sensor will detect it and inform the ECU to adjust the MAP...
    330i sport a big chunk of berlin...

     
     

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    Cant ya do a search on lambda sensors and how they work?
     
     

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    Quote Originally Posted by dailydoggy View Post
    pretty sure its the engine knock sensors that detects the fuel type from the engine detonations...as it suggests the poorer the fuel quality the more it will rattle and knock and the snsor will detect it and inform the ECU to adjust the MAP...
    Yes, I know, like I said I understand perfectly how it works when detecting knock and reducing the timing. It's the other direction I don't get.
     
     

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