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    #11
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    ya not really listening the lower the fuel quality the more the engine will knock as it detonates at a lower temp than premium fuel creating more engine knock noise, so the sensor detects that knock and tells the ECU so it knows what type of fuel is being used by the engines knock characteristics and so adjusts the ignition timing etc etc...the higher the fuel quality the engine will knock less so the ECU knows its premium fuel and it has no need to trim the ECU MAP from its base MAP to smooth the engine...
    330i sport a big chunk of berlin...

     
     

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    #12
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    Quote Originally Posted by dailydoggy View Post
    ya not really listening the lower the fuel quality the more the engine will knock as it detonates at a lower temp than premium fuel creating engine knock, so the sensor detects that knock and tells the ECU so it knows what type of fuel is being used bythe engines knock and so adjusts the igntion timing ect ect...
    I am listening, I don't think you read my original question though. I already said I fully understand how engine knock is detected and the timing is lowered, what I don't understand is how it detects that higher than regular fuel is present thus it knows it should advance the engine timing.
     
     

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    #13
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    see above...ya just not listening at all...

    low octane fuel=more engine knock
    better or higher octane fuel=less engine knock

    thats before the ECU does anything with ignition and timing to lessen the knock to keep it smoother for low octane fuel useage...
    330i sport a big chunk of berlin...

     
     

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    #14
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    Quote Originally Posted by edber View Post
    Cant ya do a search on lambda sensors and how they work?
    The wikipedia page suggests they are more to do with reducing emissions than regulating the engine timing.
     
     

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    Some people

    Go get an engineering book or spend time on youtube watching videos on your subject...explained

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    Im pretty sure the ecu keeps it on the verge of knocking as this is the most efficient point. Therefore if you put higher octane fuel in it will also adjust the other way. If you gp from 98 to 91 you dont notice it knock because it adjusts very quickly when knocking is detected.


    Sent from AutoGuide.com Free App
     
     

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    Quote Originally Posted by dailydoggy View Post
    see above...ya just not listening at all...
    So you're saying that even with 99 RON fuel the engine will still knock, just less than with regular fuel? That seems unlikely, from what I've read engine knock is bad and causes damage, most articles on fuel grade suggest that knock is unusual and only occurs when the timing is faster than the fuel grade can deal with. Poor quality fuel detonates prematurely and causes knock, and then the engine reduces the timing to compensate and eliminate the knock. I find it hard to believe that engine knock is a normal feature of a healthy engine running on premium fuel.
     
     

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    all fuel will cause an engine to knock depending on the engine design bore n stoke etc and timing, some more, some hardly at all its the ECU jobs to smooth it out once it knows what fuel its using, which info it gets from? yes youve guessed it the KNOCK SENSOR...95ron is always gonna cause the engine to knock at a set figure for said engine because of its octane content so if the ECU detects this figure from the sensor it now knows the fuel being used as its preprogrammed to recognise the knock sensor data value, so now it adjusts the engine timing to smooth it...

    same with 97ron fuel it will detect less of an initial knock from the higher octane, so it then know its 97ron being used and trims accordingly to keep knock control at a premium for the engine...
    330i sport a big chunk of berlin...

     
     

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    Quote Originally Posted by negev View Post
    The wikipedia page suggests they are more to do with reducing emissions than regulating the engine timing.
    Lambda sensors also sense the amount of oxygen which depends on a high burn rate=low oxygen=high ron or low burn rate=high oxygen=low ron.
    Much the same as doggy has already said.
     
     

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    There's a stack of different maps inside most modern ECUs, usually a couple of basic ones for high and low octane, an optimal best advance map, maps for different vanos positions and engine temps, and it'll blend them all together to come up with a result at the end.

    It will push the advance if you are running on low octane, but I can't say exactly how long it takes to switch between the high octane and low octane maps.
     
     

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