[Diy_efi] Rich detonation?
niche at iinet.net.au
Sun Nov 19 00:58:04 CST 2006
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 ?
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
> Subject: [Diy_efi] Rich detonation?
> 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?
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