[Diy_efi] Knock sensing - water injection

[Gary]

> "slowing down the burn rate' is about the opposite of what you want to
> avoid end gas detonation---

There are those that believe running a richer mixture delays the onset
of detonation, due to a cooling effect of the extra fuel.  Actually, fuel is
a
rather inefficient means of cooling the combustion mixture, especially
when compared to H2O.  Although running with a richer mix can result
in cooler operation, it is really a secondary effect, and not the true
cause.

Combustion speed reaches it's max at around 50-75*F RICH of peak
exhaust gas temp.  Either by adding additional fuel, or taking a step in
the opposite direction, by operating the engine 50-75*F LEAN of peak
exhaust gas temp, will SLOW the combustion rate, and DELAY the point
at which peak chamber pressure occurs, and go to great lengths in
eliminating the risk of detonation.  Combustion is most efficient when
the point of peak combustion pressure occurs at 16-18* ATDC.
Therefore the true reason for the delay of detonaton from richer mixture,
(or better yet, from a leaner mixture) appears to be due to the peak
combustion pressure occuring LATER.  So Bear.... AFAIC, this suggests
the frame front is being SLOWED down.   The research was performed
by General Aviation Modification, Inc. located in OK.

GAS


----- Original Message ----- 
From: "Greg Hermann" <bearbvd at mindspring.com>
To: "A list for Do-It-Yourself EFI" <diy_efi at diy-efi.org>
Sent: Thursday, February 24, 2005 8:22 PM
Subject: Re: [Diy_efi] Knock sensing - water injection


> At 10:32 AM 2/25/05, Geoff Harrison wrote:
> >Hi all.
> >IIRC, knocking = pre-ignition = detonation,
>
> NOPE.
>
> Pre-ignition does NOT equal detonation.
>
> The other things which you are stating as 'sort-of' facts are also pretty
> wildly distorted.
>
> If you look through the archives, there is PLENTY of info on what H2O
> injection can do, and why it does it. Your so-called 'rate of expansion'
> ain't it at all--but water's very high latent heat of vaporization has
> quite a lot to do with it--as does its ability to facilitate hydrocarbon
> combustion.
>
> "slowing down the burn rate' is about the opposite of what you want to
> avoid end gas detonation---
>
> Greg


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