[Diy_efi] Knock sensing - water injection

Greg Hermann bearbvd at mindspring.com
Fri Feb 25 06:20:09 GMT 2005


At 11:10 PM 2/24/05, Daniel Nicoson wrote:

Dan--

You should actually make more power at about 14.2 than at 14.7 with the WI.
At a slight penalty in bsfc. This is because with the slightly richer
mixture, you will selectively burn hydrogen and add the first O to the
carbon. Adding the second O to carbon--to get from CO to CO2-- gives less
heat of combustion than the prior steps do, thus the gain in power with the
slightly rich of stoich mixture for a given amount of O2 getting pumped
through the motor.

Greg

>I've been working on a sequential water injection system for almost two
>years now.  I did 21 dyno pulls last fall testing out a few ideas.  I was
>able to show about a 10% fuel savings at high load by running a very lean
>mixture (14.7) and making up the internal cooling with the water.
>
>When the snow goes away, I'm going to use the same system to experiment with
>30% nitro and 70% methanol, see if I can make more power on account of the
>nitro...
>
>Lots of WI info on the web.  Several interesting papers in the NACA archives
>from WWII aircraft research.  Google.  Google.
>
>All my dyno stuff and possibly those NACA papers are on my web site
>www.myo-p.com
>
>Have fun.
>
>Dan Nicoson
>
>
>-----Original Message-----
>From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
>Behalf Of Gary
>Sent: Thursday, February 24, 2005 10:28 PM
>To: A list for Do-It-Yourself EFI
>Subject: Re: [Diy_efi] Knock sensing - water injection
>
>
>> "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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