water into efi system before injectors.

[Mike (Perth, Western Australia)]

At 08:11 AM 14/3/2000 -0700, bearbvd at cmn.net (Greg Hermann) wrote:
>>mmm Can you clarify - for say 100ml of fuel flow per minute you want
>>75 to 85 ml water flow ?
>
>!00 GRAMS of fuel flow would equate to 75 or 85 GRAMS of fuel flow--the
>water is denser than the fuel, though.

Of course by 0.78 or thereabouts...

>Precisely. What is going on is the compression stroke begins to act a lot
>more like an isothermal process than an adiabatic one. Consequently, much
>less power goes into the compression stroke. Temperature at TDC (ignition
>event) is MUCH lower--on the order of 235 to 250 degrees F, instead of 900
>degrees or so.

That seems like a *very* large difference - can you approximate the minimum
level of water injection for the largest drop in TDC temperature ?

>Lower peak temp after burn means less power available on the expansion
>(power) stroke, but this is more than completely balanced by the lower
>negative power on the compression stroke. (About 1.5% net gain.)

This may well explain why many who try WI say - "it makes no difference"
or the "difference is hardly worth it" - when the reality is its an
alteration of the combustion putting less overall stress on the chamber etc.

>Lower peak cycle temp means significantly lower losses to water jackets,
>though, so net gain becomes still greater.
>
>Durability is of course significantly improved with the lower temps.

Thats something I wanted to impart to a local chap (not net savy) who
says "just add more fuel instead" to get rid of pinging, when I'm
suggesting the heat of vaporisation is useful to reduce charge temp
and WI will improve fuel economy over just adding fuel to stop pinging.

Here is a classic case of practical experience not showing the whole
story - unless we could measure instantaneous temp in chamber at TDC.
Because the average outcome looks the same as before WI - most people
dismiss it as a waste of time and point to risk of corrosion to engine
and exhaust from Nitric acids - reality is less Nox produced due to lower
charge temp...There's also the inconvenience factor of adding water
all the time.

Does it really have to be distilled water - can regular tap water be
used given the turbulence in the chamber would likely flush out most
deposits.

One local did say that using WI for long periods results in far less
carbon buildups in the chamber.

>Lower temps and lower partial air and fuel vapor pressures at TDC help
>avoid detonation, and there is also the detonation resistance added by the
>highly polar chemical nature of the water molecules themselves  and that
>effect on the free radical detonation precursor molecules during the
>combustion process itself.

Interesting, never knew that - great description.

>Basically this means that with higher compression ratio, there is more work
>available to provide latent heat with which to evaporate the water.
>
>Lots of folks don't realize that engines running straight methanol fuel
>have _NOT_ evaporated all of the fuel at TDC!! Not enough work available to
>provide the needed latent heat! The first part of the burn provides heat to
>finish evaporating the fuel.

mmm - Tah - never knew that either

>>Has anyone published any actual curves, water flow vs power vs CR vs Fuel
>>or anything even similar ?
>
>Never seen any, Riccardo published as much as I have seen.

Don't know of that - any pointers ?

Rgds

:) mike


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