[Diy_efi] Rich detonation?

vg30dett at portugalmail.com vg30dett
Sun Nov 19 21:22:35 UTC 2006


F1 engines dont run on alchool...AFAIK.

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
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