>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>On Behalf Of Gerhard Fiedler
>Sent: 28 June 2007 14:43
>To: piclist@mit.edu
>Subject: Re: [EE] Simple fuel-saver, so they say lean mixture
>
>
>Lee Jones wrote:
>
>>> I don't know the difference between burn fast and explode.  
>Does fuel 
>>> burn fast and if the engine flies apart then the fuel was 
>"exploding" 
>>> ?
>> 
>> Modern engines have a knock sensor.  The computer controller 
>leans the 
>> air-fuel mixture as much as possible, usually based on an O2 
>sensor in 
>> the exhaust system.  When it senses the fuel exploding via the knock 
>> sensor, it enrichens the mixture "enough" to stop it.
>
>I don't think the "knocking" is fuel exploding. AFAIK it is 
>fuel expanding before the piston reached its end position. 
>IIRC, you can make any engine knock without changing the 
>mixture, just by moving the ignition point forward. And you 
>can make it stop knocking by moving the point back. Since the 
>time between the spark and the mixture expanding depends on 
>many factors, and you want the mixture to start expanding 
>right after the piston reached the dead point but not before, 
>they control the ignition point now with knock sensors.

http://www.motorcycle.com/how-to/wrenching-with-robchemical-soup-the-mystery-of-detonation-3420.html

Regards

Mike


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