[Diy_efi] Rich detonation?

[Mike]

Is the rationale for what you say below, excess fuel, or can you
articulate just why the detonation occurs. I understand F1 engines
often shift to  use 4:1 afr (with methanol) and although there is reduced power
than running at just better than stoich for methanol - that the 4:1 ratio
still results in combustion but radically reduce stresses on exhaust
valves - vis a vis cooling the valves immediately after a hard run where the
integral of EGT over the last few seconds exceeds some maxima ?

Rgds

Mike

At 08:43 AM 11/19/06, you wrote:
>Hi, Joe!  It's Damon (flyboy) from the MR2 community.  
> 
>Yes, it's totally possible to get rich detonation.  However, you will usually misfire before you hit this point, unless you are pretty careless with the ignition.  
> 
>Combustion velocity is what dictates spark timing, and it varies with AFR.  The max velocity is around 11.0 mass air/fuel ratio (the exact value is debatable, but the concept still holds).  Therefore, rich of this value, the combustion velocity increases again, necessitating a reduced spark advance.  
> 
>If you leave the spark static and add fuel, then very rich mixtures will detonate, assuming the detonation propensity was there to begin with.  
>
>        -----Original Message----- 
>        From: diy_efi-bounces at diy-efi.org on behalf of Joseph Obernberger 
>        Sent: Sat 11/18/2006 3:10 PM 
>        To: diy_efi at diy-efi.org 
>        Cc: 
>        Subject: [Diy_efi] Rich detonation?
>        
>        
>
>        Hi,
>            I've read in various places that it is possible to run an engine so
>        rich that detonation can occur - or at least the knock sensor would pick
>        up what sounded like detonation.  Has anyone ever experienced this?  Any
>        truth to it?
>        Thanks!
>        
>        -Joe
>        http://www.lovehorsepower.com
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