[Diy_efi] Rich detonation?

[Mike]

At 05:22 AM 11/20/06, you wrote:
>F1 engines dont run on alchool...AFAIK.

ok, I might have been thinking of nascar then, long time ago ~`:o

However, I recall that in respect of F1, the AFR shifted from
just over stoich to 4:1 as that thermal management tool mentioned,
which raises the question - where is this "rich detonation" in that
environment has it been sidestepped, did it exist in the first place ?

Is "rich detonation" a clearly defined effect. Or is it perhaps a consequence
of running very rich, causing huge carbon buildup then when normal stoich
occurs these carbon deposits cause pre-ignition which is interpreted
as if its detonation as it appears to be (closely) caused by the rich
condition - until such time as the preignition or detonation scours most
of the carbon off the various surfaces ?

So what is the mechanism of "rich detonation" ?

rgds

Mike





>Citando "Becker, Damon \\(Damon\\)" <damonb at avaya.com>:
>
> I'm not sure what you mean by "shift to use 4:1".  I'm assuming you mean mass
> ratio, and "shift" means they moved to using that ratio, instead of being
> associated with gear shifts.  
>  
> AFR is definitely a thermal management tool, among other things.  What you say
> does make sense if you are seeing excessive EGT.  If you can infer exhaust
> valve temp from an integral of the EGT, then that response would definitely
> make sense.  This doesn't really have much to do with detonation, though.  
>  
> I'm sure the exact AFR (or lambda) that peak combustion speeds happen differ
> with fuel.  Although I haven't seen research to this effect, I'm sure it's the
> case.  I have no idea where 4:1 mass ratio methanol falls on the combustion
> speed charts, as I haven't played with methanol.  
> 
>        -----Original Message----- 
>        From: diy_efi-bounces at diy-efi.org on behalf of Mike 
>        Sent: Sat 11/18/2006 11:58 PM 
>        To: diy_efi at diy-efi.org 
>        Cc: 
>        Subject: RE: [Diy_efi] Rich detonation?
>        
>        
> 
>        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
>        >        _______________________________________________
>        >        Diy_efi mailing list
>        >        Diy_efi at diy-efi.org
>        >        Subscribe: http://lists.diy-efi.org/mailman/listinfo/diy_efi
>        >        Main WWW page:  http://www.diy-efi.org/diy_efi
>        >       
>        >
>        >_______________________________________________
>        >Diy_efi mailing list
>        >Diy_efi at diy-efi.org
>        >Subscribe: http://lists.diy-efi.org/mailman/listinfo/diy_efi
>        >Main WWW page:  http://www.diy-efi.org/diy_efi
>        _______________________________________________
>        Diy_efi mailing list
>        Diy_efi at diy-efi.org
>        Subscribe: http://lists.diy-efi.org/mailman/listinfo/diy_efi
>        Main WWW page:  http://www.diy-efi.org/diy_efi
>        
> 
> 
>
>
>
>__________________________________________________________
>Pare de esbanjar dinheiro!
>Compare o pre?o da sua liga??o ? Internet
>http://acesso.portugalmail.pt/maisbarato
>_______________________________________________
>Diy_efi mailing list
>Diy_efi at diy-efi.org
>Subscribe: http://lists.diy-efi.org/mailman/listinfo/diy_efi
>Main WWW page:  http://www.diy-efi.org/diy_efi